aboutsummaryrefslogtreecommitdiffhomepage
path: root/docs/SkPixmap_Reference.bmh
blob: 86d89e53d1fd6f7b31bf4f554fac744b99339e3d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
#Topic Pixmap
#Alias Pixmap_Reference

#Subtopic Overview
    #Subtopic Subtopic
    #Populate
    ##
##

#Class SkPixmap

Pixmap provides a utility to pair SkImageInfo with pixels and row bytes. 
Pixmap is a low level class which provides convenience functions to access
raster destinations. Canvas can not draw Pixmap, nor does Pixmap provide
a direct drawing destination.

Use Bitmap to draw pixels referenced by Pixmap; use Surface to draw into
pixels referenced by Pixmap.

Pixmap does not try to manage the lifetime of the pixel memory. Use Pixel_Ref
to manage pixel memory; Pixel_Ref is safe across threads.

#Subtopic Related_Function
#Populate
##

#Subtopic Constructor
#Populate
##

#Subtopic Member_Function
#Populate
##

#Subtopic Initialization
#Line # sets fields for use ##

# ------------------------------------------------------------------------------

#Method SkPixmap()

#In Initialization
#Line # constructs with default values ##
Creates an empty Pixmap without pixels, with kUnknown_SkColorType, with
kUnknown_SkAlphaType, and with a width and height of zero. Use
reset() to associate pixels, SkColorType, SkAlphaType, width, and height
after Pixmap has been created.

#Return empty Pixmap ##

#Example
void draw(SkCanvas* canvas) {
    const char* alphas[] = {"Unknown", "Opaque", "Premul", "Unpremul"};
    const char* colors[] = {"Unknown", "Alpha_8", "RGB_565", "ARGB_4444", "RGBA_8888", "RGB_888x",
                            "BGRA_8888", "RGBA_1010102", "RGB_101010x", "Gray_8", "RGBA_F16"};
    SkPixmap pixmap;
    for (int i = 0; i < 2; ++i) {
       SkDebugf("width: %2d  height: %2d", pixmap.width(), pixmap.height());
       SkDebugf("  color: k%s_SkColorType", colors[pixmap.colorType()]);
       SkDebugf("  alpha: k%s_SkAlphaType\n", alphas[pixmap.alphaType()]);
       pixmap.reset(SkImageInfo::Make(25, 35, kRGBA_8888_SkColorType, kOpaque_SkAlphaType),
                    nullptr, 0);
    }
}
#StdOut
width:  0  height:  0  color: kUnknown_SkColorType  alpha: kUnknown_SkAlphaType
width: 25  height: 35  color: kRGBA_8888_SkColorType  alpha: kOpaque_SkAlphaType
##
##

#SeeAlso SkPixmap(const SkImageInfo& info, const void* addr, size_t rowBytes) reset() SkAlphaType SkColorType

##

# ------------------------------------------------------------------------------

#Method SkPixmap(const SkImageInfo& info, const void* addr, size_t rowBytes)
        
#In Initialization
#Line # constructs from Image_Info, pixels ##
Creates Pixmap from info width, height, SkAlphaType, and SkColorType.
addr points to pixels, or nullptr. rowBytes should be info.width() times
info.bytesPerPixel(), or larger.

No parameter checking is performed; it is up to the caller to ensure that
addr and rowBytes agree with info.  

The memory lifetime of pixels is managed by the caller. When Pixmap goes
out of scope, addr is unaffected.

Pixmap may be later modified by reset() to change its size, pixel type, or
storage.

#Param info  width, height, SkAlphaType, SkColorType of Image_Info ##
#Param addr  pointer to pixels allocated by caller; may be nullptr ##
#Param rowBytes  size of one row of addr; width times pixel size, or larger ##

#Return initialized Pixmap ##

#Example
#Image 3
#Description
SkImage::MakeRasterCopy takes const SkPixmap& as an argument. The example 
constructs a SkPixmap from the brace-delimited parameters.
##
    SkDebugf("image alpha only = %s\n", image->isAlphaOnly() ? "true" : "false");
    SkPMColor pmColors = 0;
    sk_sp<SkImage> copy = SkImage::MakeRasterCopy({SkImageInfo::MakeA8(1, 1),
                                                  (uint8_t*)&pmColors,
                                                  1});
    SkDebugf("copy alpha only = %s\n", copy->isAlphaOnly() ? "true" : "false");
#StdOut
image alpha only = false
copy alpha only = true
##
##

#SeeAlso SkPixmap() reset() SkAlphaType SkColorType

##

# ------------------------------------------------------------------------------

#Method void reset()

#In Initialization
#Line # reuses existing Pixmap with replacement values ##
Sets width, height, row bytes to zero; pixel address to nullptr; SkColorType to 
kUnknown_SkColorType; and SkAlphaType to kUnknown_SkAlphaType.

The prior pixels are unaffected; it is up to the caller to release pixels
memory if desired.

#Example
void draw(SkCanvas* canvas) {
    const char* alphas[] = {"Unknown", "Opaque", "Premul", "Unpremul"};
    const char* colors[] = {"Unknown", "Alpha_8", "RGB_565", "ARGB_4444", "RGBA_8888", "RGB_888x",
                            "BGRA_8888", "RGBA_1010102", "RGB_101010x", "Gray_8", "RGBA_F16"};
    SkPixmap pixmap(SkImageInfo::Make(25, 35, kRGBA_8888_SkColorType, kOpaque_SkAlphaType),
                    nullptr, 0);
    for (int i = 0; i < 2; ++i) {
       SkDebugf("width: %2d  height: %2d", pixmap.width(), pixmap.height());
       SkDebugf("  color: k%s_SkColorType", colors[pixmap.colorType()]);
       SkDebugf("  alpha: k%s_SkAlphaType\n", alphas[pixmap.alphaType()]);
       pixmap.reset();
    }
}
#StdOut
width: 25  height: 35  color: kRGBA_8888_SkColorType  alpha: kOpaque_SkAlphaType
width:  0  height:  0  color: kUnknown_SkColorType  alpha: kUnknown_SkAlphaType
##
##

#SeeAlso SkPixmap() SkAlphaType SkColorType

##

# ------------------------------------------------------------------------------

#Method void reset(const SkImageInfo& info, const void* addr, size_t rowBytes)

#In Initialization
Sets width, height, SkAlphaType, and SkColorType from info.
Sets pixel address from addr, which may be nullptr. 
Sets row bytes from rowBytes, which should be info.width() times
info.bytesPerPixel(), or larger.

Does not check addr. Asserts if built with SK_DEBUG defined and if rowBytes is
too small to hold one row of pixels.  

The memory lifetime pixels are managed by the caller. When Pixmap goes
out of scope, addr is unaffected.

#Param info  width, height, SkAlphaType, SkColorType of Image_Info ##
#Param addr  pointer to pixels allocated by caller; may be nullptr ##
#Param rowBytes  size of one row of addr; width times pixel size, or larger ##

#Example
#Image 4
#Height 64
void draw(SkCanvas* canvas) {
    std::vector<int32_t> pixels;
    pixels.resize(image->height() * image->width() * 4);
    SkPixmap pixmap(SkImageInfo::Make(image->width(), image->height(), kN32_SkColorType,
            image->alphaType()), (const void*) &pixels.front(), image->width() * 4);
    image->readPixels(pixmap, 0, 0);
    int x = 0;
    for (auto colorType : { kRGBA_8888_SkColorType, kBGRA_8888_SkColorType } ) {
        pixmap.reset(SkImageInfo::Make(image->width(), image->height(), colorType, 
                image->alphaType()), (const void*) &pixels.front(), image->width() * 4);
        SkBitmap bitmap;
        bitmap.installPixels(pixmap);
        canvas->drawBitmap(bitmap, x, 0);
        x += 128;
    }
}
##

#SeeAlso SkPixmap(const SkImageInfo& info, const void* addr, size_t rowBytes) reset() SkAlphaType SkColorType

##

# ------------------------------------------------------------------------------

#Method void setColorSpace(sk_sp<SkColorSpace> colorSpace)

#In Initialization
#Line # sets Image_Info Color_Space ##

Changes Color_Space in Image_Info; preserves width, height, SkAlphaType, and
SkColorType in Image, and leaves pixel address and row bytes unchanged.
Color_Space reference count is incremented.

#Param colorSpace  Color_Space moved to Image_Info ##

#Example
void draw(SkCanvas* canvas) {
    SkPixmap pixmap;
    sk_sp<SkColorSpace> colorSpace1 = SkColorSpace::MakeRGB(SkColorSpace::kLinear_RenderTargetGamma,
                                                            SkColorSpace::kRec2020_Gamut);
    SkDebugf("is %sunique\n", colorSpace1->unique() ? "" : "not "); 
    pixmap.setColorSpace(colorSpace1);
    SkDebugf("is %sunique\n", colorSpace1->unique() ? "" : "not ");   
}
#StdOut
is unique
is not unique
##
##

#SeeAlso Color_Space SkImageInfo::makeColorSpace

##

# ------------------------------------------------------------------------------

#Method bool SK_WARN_UNUSED_RESULT reset(const SkMask& mask)
#Deprecated soon
##

# ------------------------------------------------------------------------------

#Method bool SK_WARN_UNUSED_RESULT extractSubset(SkPixmap* subset, const SkIRect& area) const

#In Initialization
#Line # sets pointer to portion of original ##
Sets subset width, height, pixel address to intersection of Pixmap with area,
if intersection is not empty; and return true. Otherwise, leave subset unchanged
and return false. 

Failing to read the return value generates a compile time warning.

#Param subset  storage for width, height, pixel address of intersection ##
#Param area    bounds to intersect with Pixmap ##

#Return true if intersection of Pixmap and area is not empty ##

#Example
#Image 3
#Height 128
void draw(SkCanvas* canvas) {
    std::vector<int32_t> pixels;
    pixels.resize(image->height() * image->width() * 4);
    SkPixmap pixmap(SkImageInfo::Make(image->width(), image->height(), kN32_SkColorType,
            image->alphaType()), (const void*) &pixels.front(), image->width() * 4);
    image->readPixels(pixmap, 0, 0);
    SkPixmap inset;
    if (pixmap.extractSubset(&inset, {128, 128, 512, 512})) {
        SkBitmap bitmap;
        bitmap.installPixels(inset);
        canvas->drawBitmap(bitmap, 0, 0);
    }
}
##

#SeeAlso reset() SkIRect::intersect

##

#Subtopic Initialization ##

#Subtopic Image_Info_Access
#Line # returns all or part of Image_Info ##

# ------------------------------------------------------------------------------

#Method const SkImageInfo& info() const 

#In Image_Info_Access
#Line # returns Image_Info ##
Returns width, height, Alpha_Type, Color_Type, and Color_Space.

#Return reference to ImageInfo  ##

#Example
#Image 3
    std::vector<int32_t> pixels;
    pixels.resize(image->height() * image->width() * 4);
    SkPixmap pixmap(SkImageInfo::Make(image->width(), image->height(), kN32_SkColorType,
            image->alphaType()), (const void*) &pixels.front(), image->width() * 4);
    image->readPixels(pixmap, 0, 0);
    SkPixmap inset;
    if (pixmap.extractSubset(&inset, {128, 128, 512, 512})) {
        const SkImageInfo& info = inset.info();
        const char* alphas[] = {"Unknown", "Opaque", "Premul", "Unpremul"};
        const char* colors[] = {"Unknown", "Alpha_8", "RGB_565", "ARGB_4444", "RGBA_8888",
                "RGB_888x", "BGRA_8888", "RGBA_1010102", "RGB_101010x", "Gray_8", "RGBA_F16"};
        SkDebugf("width: %d height: %d color: %s alpha: %s\n", info.width(), info.height(),
                 colors[info.colorType()], alphas[info.alphaType()]);
    }
#StdOut
width: 384 height: 384 color: BGRA_8888 alpha: Opaque
##
##

#SeeAlso Image_Info

##

# ------------------------------------------------------------------------------

#Method size_t rowBytes() const 

#In Image_Info_Access
#Line # returns interval between rows in bytes ##
Returns row bytes, the interval from one pixel row to the next. Row bytes
is at least as large as: 
#Formula
width() * info().bytesPerPixel()
##
.

Returns zero if colorType is kUnknown_SkColorType.
It is up to the Bitmap creator to ensure that row bytes is a useful value.

#Return  byte length of pixel row ##

#Example
SkPixmap badPixmap = {SkImageInfo::MakeA8(4, 4), nullptr, 2};
SkPixmap okPixmap = {SkImageInfo::MakeA8(4, 4), nullptr, 8};
for (auto& pixmap : { badPixmap, okPixmap } ) {
    SkDebugf("rowBytes: %d minRowBytes: %d\n", pixmap.rowBytes(), 
       pixmap.info().minRowBytes());
}
#StdOut
rowBytes: 2 minRowBytes: 4
rowBytes: 8 minRowBytes: 4
##
##

#SeeAlso addr() info() SkImageInfo::minRowBytes

##

# ------------------------------------------------------------------------------

#Method const void* addr() const 

#In Image_Info_Access
#Line # returns readable pixel address as void pointer ##
Returns pixel address, the base address corresponding to the pixel origin.

It is up to the Pixmap creator to ensure that pixel address is a useful value.

#Return  pixel address ##

#Example
#Image 3
    std::vector<int32_t> pixels;
    pixels.resize(image->height() * image->width() * 4);
    SkPixmap pixmap(SkImageInfo::Make(image->width(), image->height(), kN32_SkColorType,
            image->alphaType()), (const void*) &pixels.front(), image->width() * 4);
    image->readPixels(pixmap, 0, 0);
    SkDebugf("pixels address: 0x%llx\n", pixmap.addr());
    SkPixmap inset;
    if (pixmap.extractSubset(&inset, {128, 128, 512, 512})) {
         SkDebugf("inset address:  0x%llx\n", inset.addr());
    }
#StdOut
#Volatile
pixels address: 0x7f2a440bb010
inset address:  0x7f2a440fb210
##
##

#SeeAlso addr(int x, int y) addr8 addr16 addr32 addr64 info() rowBytes()

##

# ------------------------------------------------------------------------------

#Method int width() const 

#In Image_Info_Access
#Line # returns pixel column count ##
Returns pixel count in each pixel row. Should be equal or less than:

#Formula
rowBytes() / info().bytesPerPixel()
##
. 

#Return  pixel width in Image_Info ##

#Example
    SkImageInfo info = SkImageInfo::MakeA8(16, 32);
    SkPixmap pixmap(info, nullptr, 64);
    SkDebugf("pixmap width: %d  info width: %d\n", pixmap.width(), info.width());
#StdOut
pixmap width: 16  info width: 16
##
##

#SeeAlso height() SkImageInfo::width()

##

# ------------------------------------------------------------------------------

#Method int height() const 

#In Image_Info_Access
#Line # returns pixel row count ##
Returns pixel row count.

#Return  pixel height in Image_Info ##

#Example
    SkPixmap pixmap(SkImageInfo::MakeA8(16, 32), nullptr, 64);
    SkDebugf("pixmap height: %d  info height: %d\n", pixmap.height(), pixmap.info().height());
#StdOut
pixmap height: 32  info height: 32
##
##

#SeeAlso width() ImageInfo::height()

##

# ------------------------------------------------------------------------------

#Method SkColorType colorType() const 

#In Image_Info_Access
#Line # returns Image_Info Color_Type ##
Returns Color_Type, one of: #list_of_color_types#.

#Return  Color_Type in Image_Info ##

#Example
    const char* colors[] = {"Unknown", "Alpha_8", "RGB_565", "ARGB_4444", "RGBA_8888", "RGB_888x",
                            "BGRA_8888", "RGBA_1010102", "RGB_101010x", "Gray_8", "RGBA_F16"};
    SkPixmap pixmap(SkImageInfo::MakeA8(16, 32), nullptr, 64);
    SkDebugf("color type: k" "%s" "_SkColorType\n", colors[pixmap.colorType()]);
#StdOut
color type: kAlpha_8_SkColorType
##
##

#SeeAlso alphaType() SkImageInfo::colorType

##

# ------------------------------------------------------------------------------

#Method SkAlphaType alphaType() const 

#In Image_Info_Access
#Line # returns Image_Info Alpha_Type ##
Returns Alpha_Type, one of: kUnknown_SkAlphaType, kOpaque_SkAlphaType,
kPremul_SkAlphaType, kUnpremul_SkAlphaType.

#Return  Alpha_Type in Image_Info ##

#Example
    const char* alphas[] = {"Unknown", "Opaque", "Premul", "Unpremul"};
    SkPixmap pixmap(SkImageInfo::MakeA8(16, 32), nullptr, 64);
    SkDebugf("alpha type: k" "%s" "_SkAlphaType\n", alphas[pixmap.alphaType()]);
#StdOut
alpha type: kPremul_SkAlphaType
##
##

#SeeAlso colorType() SkImageInfo::alphaType

##

# ------------------------------------------------------------------------------

#Method SkColorSpace* colorSpace() const 

#In Image_Info_Access
#Line # returns Image_Info Color_Space ##
Returns Color_Space associated with Image_Info. The
reference count of Color_Space is unchanged. The returned Color_Space is
immutable.

#Return Color_Space, the range of colors, in Image_Info ##

#Example
#Description
SkColorSpace::MakeSRGBLinear creates Color_Space with linear gamma
and an sRGB gamut. This Color_Space gamma is not close to sRGB gamma.
##
    SkPixmap pixmap(SkImageInfo::MakeN32(16, 32, kPremul_SkAlphaType, 
            SkColorSpace::MakeSRGBLinear()), nullptr, 64);
    SkColorSpace* colorSpace = pixmap.colorSpace();
    SkDebugf("gammaCloseToSRGB: %s  gammaIsLinear: %s  isSRGB: %s\n",
            colorSpace->gammaCloseToSRGB() ? "true" : "false",
            colorSpace->gammaIsLinear() ? "true" : "false",
            colorSpace->isSRGB() ? "true" : "false");
#StdOut
gammaCloseToSRGB: false  gammaIsLinear: true  isSRGB: false
##
##

#SeeAlso Color_Space SkImageInfo::colorSpace

##

# ------------------------------------------------------------------------------

#Method bool isOpaque() const 

#In Image_Info_Access
#Line # returns true if Image_Info describes opaque pixels ##
Returns true if Alpha_Type is kOpaque_SkAlphaType.
Does not check if Color_Type allows Alpha, or if any pixel value has
transparency.

#Return true if Image_Info has opaque Alpha_Type ##

#Example
#Description
    isOpaque ignores whether all pixels are opaque or not.
##
    std::vector<uint32_t> pixels;
    const int height = 2;
    const int width = 2;
    pixels.resize(height * width * 4);
    SkPixmap pixmap(SkImageInfo::Make(width, height, kN32_SkColorType,
            kPremul_SkAlphaType), (const void*) &pixels.front(), width * 4);
    for (int index = 0; index < 2; ++index) {
        pixmap.erase(0x00000000);
        SkDebugf("isOpaque: %s\n", pixmap.isOpaque() ? "true" : "false");
        pixmap.erase(0xFFFFFFFF);
        SkDebugf("isOpaque: %s\n", pixmap.isOpaque() ? "true" : "false");
        pixmap.reset(pixmap.info().makeAlphaType(kOpaque_SkAlphaType),
                     (const void*) &pixels.front(), width * 4);
    }
#StdOut
isOpaque: false
isOpaque: false
isOpaque: true
isOpaque: true
##
##

#SeeAlso computeIsOpaque SkImageInfo::isOpaque

##

# ------------------------------------------------------------------------------

#Method SkIRect bounds() const 

#In Image_Info_Access
#Line # returns width and height as Rectangle ##
Returns IRect { 0, 0, width(), height() }.

#Return  integral rectangle from origin to width() and height() ##

#Example
    for (int width : { 0, 2 } ) {
        for (int height : { 0, 2 } ) {
             SkPixmap pixmap(SkImageInfo::MakeA8(width, height), nullptr, width);
             SkDebugf("width: %d height: %d empty: %s\n", width, height,
                      pixmap.bounds().isEmpty() ? "true" : "false");
        }
    }
#StdOut
width: 0 height: 0 empty: true
width: 0 height: 2 empty: true
width: 2 height: 0 empty: true
width: 2 height: 2 empty: false
##
##

#SeeAlso height() width() IRect 

##

# ------------------------------------------------------------------------------

#Method int rowBytesAsPixels() const 

#In Image_Info_Access
#Line # returns interval between rows in pixels ##

Returns number of pixels that fit on row. Should be greater than or equal to
width().

#Return  maximum pixels per row ##

#Example
    for (int rowBytes : { 4, 5, 6, 7, 8} ) {
        SkPixmap pixmap(SkImageInfo::MakeN32(1, 1, kPremul_SkAlphaType), nullptr, rowBytes);
        SkDebugf("rowBytes: %d rowBytesAsPixels: %d\n", rowBytes, pixmap.rowBytesAsPixels());
    }
#StdOut
rowBytes: 4 rowBytesAsPixels: 1
rowBytes: 5 rowBytesAsPixels: 1
rowBytes: 6 rowBytesAsPixels: 1
rowBytes: 7 rowBytesAsPixels: 1
rowBytes: 8 rowBytesAsPixels: 2
##
##

#SeeAlso rowBytes shiftPerPixel width SkImageInfo::bytesPerPixel

##

# ------------------------------------------------------------------------------

#Method int shiftPerPixel() const 

#In Image_Info_Access
#Line # returns bit shift from pixels to bytes ##
Returns bit shift converting row bytes to row pixels.
Returns zero for kUnknown_SkColorType.

#Return one of: 0, 1, 2, 3; left shift to convert pixels to bytes ##

#Example
    const char* colors[] = {"Unknown", "Alpha_8", "RGB_565", "ARGB_4444", "RGBA_8888", "RGB_888x",
                            "BGRA_8888", "RGBA_1010102", "RGB_101010x", "Gray_8", "RGBA_F16"};
    SkImageInfo info = SkImageInfo::MakeA8(1, 1);
    for (SkColorType colorType : { kUnknown_SkColorType,   kAlpha_8_SkColorType,
                                   kRGB_565_SkColorType,   kARGB_4444_SkColorType, 
                                   kRGBA_8888_SkColorType, kBGRA_8888_SkColorType,
                                   kGray_8_SkColorType,    kRGBA_F16_SkColorType } ) {
        SkPixmap pixmap(info.makeColorType(colorType), nullptr, 4);
        SkDebugf("color: k" "%s" "_SkColorType" "%*s" "bytesPerPixel: %d shiftPerPixel: %d\n",
                colors[colorType], 10 - strlen(colors[colorType]), " ",
                pixmap.info().bytesPerPixel(), pixmap.shiftPerPixel());
    }
#StdOut
color: kUnknown_SkColorType   bytesPerPixel: 0 shiftPerPixel: 0
color: kAlpha_8_SkColorType   bytesPerPixel: 1 shiftPerPixel: 0
color: kRGB_565_SkColorType   bytesPerPixel: 2 shiftPerPixel: 1
color: kARGB_4444_SkColorType bytesPerPixel: 2 shiftPerPixel: 1
color: kRGBA_8888_SkColorType bytesPerPixel: 4 shiftPerPixel: 2
color: kBGRA_8888_SkColorType bytesPerPixel: 4 shiftPerPixel: 2
color: kGray_8_SkColorType    bytesPerPixel: 1 shiftPerPixel: 0
color: kRGBA_F16_SkColorType  bytesPerPixel: 8 shiftPerPixel: 3
##
##

#SeeAlso rowBytes rowBytesAsPixels width SkImageInfo::bytesPerPixel

##

# ------------------------------------------------------------------------------

#Method size_t computeByteSize() const

#In Image_Info_Access
#Line # returns size required for pixels ##
Returns minimum memory required for pixel storage.
Does not include unused memory on last row when rowBytesAsPixels exceeds width().
Returns zero if result does not fit in size_t.
Returns zero if height() or width() is 0.
Returns height() times rowBytes if colorType is kUnknown_SkColorType.

#Return size in bytes of image buffer ##

#Example
    SkPixmap pixmap;
    for (int width : { 1, 1000, 1000000 } ) {
        for (int height: { 1, 1000, 1000000 } ) {
            SkImageInfo imageInfo = SkImageInfo::MakeN32(width, height, kPremul_SkAlphaType);
            pixmap.reset(imageInfo, nullptr, width * 5);
            SkDebugf("width: %7d height: %7d computeByteSize: %13lld\n", width, height,
                     pixmap.computeByteSize());
        }
    }
#StdOut
width:       1 height:       1 computeByteSize:             4
width:       1 height:    1000 computeByteSize:          4999
width:       1 height: 1000000 computeByteSize:       4999999
width:    1000 height:       1 computeByteSize:          4000
width:    1000 height:    1000 computeByteSize:       4999000
width:    1000 height: 1000000 computeByteSize:    4999999000
width: 1000000 height:       1 computeByteSize:       4000000
width: 1000000 height:    1000 computeByteSize:    4999000000
width: 1000000 height: 1000000 computeByteSize: 4999999000000
##
##

#SeeAlso SkImageInfo::computeByteSize

##

#Subtopic Image_Info_Access ##

#Subtopic Reader
#Line # examine pixel value ##

# ------------------------------------------------------------------------------

#Method bool computeIsOpaque() const

#In Reader
#Line # returns true if all pixels are opaque ##
Returns true if all pixels are opaque. Color_Type determines how pixels
are encoded, and whether pixel describes Alpha. Returns true for Color_Types
without alpha in each pixel; for other Color_Types, returns true if all
pixels have alpha values equivalent to 1.0 or greater.

For Color_Types kRGB_565_SkColorType or kGray_8_SkColorType: always
returns true. For Color_Types kAlpha_8_SkColorType, kBGRA_8888_SkColorType,
kRGBA_8888_SkColorType: returns true if all pixel Alpha values are 255.
For Color_Type kARGB_4444_SkColorType: returns true if all pixel Alpha values are 15.
For kRGBA_F16_SkColorType: returns true if all pixel Alpha values are 1.0 or
greater.

Returns false for kUnknown_SkColorType. 

#Return true if all pixels have opaque values or Color_Type is opaque  ##

#Example
    std::vector<uint32_t> pixels;
    const int height = 2;
    const int width = 2;
    pixels.resize(height * width * 4);
    SkPixmap pixmap(SkImageInfo::Make(width, height, kN32_SkColorType,
            kPremul_SkAlphaType), (const void*) &pixels.front(), width * 4);
    for (int index = 0; index < 2; ++index) {
        pixmap.erase(0x00000000);
        SkDebugf("computeIsOpaque: %s\n", pixmap.computeIsOpaque() ? "true" : "false");
        pixmap.erase(0xFFFFFFFF);
        SkDebugf("computeIsOpaque: %s\n", pixmap.computeIsOpaque() ? "true" : "false");
        pixmap.reset(pixmap.info().makeAlphaType(kOpaque_SkAlphaType),
                     (const void*) &pixels.front(), width * 4);
    }
#StdOut
computeIsOpaque: false
computeIsOpaque: true
computeIsOpaque: false
computeIsOpaque: true
##
##

#SeeAlso isOpaque Color_Type Alpha

##

# ------------------------------------------------------------------------------

#Method SkColor getColor(int x, int y) const

#In Reader
#Line # returns one pixel as Unpremultiplied Color ##
Returns pixel at (x, y) as Unpremultiplied Color.
Returns black with Alpha if Color_Type is kAlpha_8_SkColorType.

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined; and returns undefined values or may crash if
SK_RELEASE is defined. Fails if Color_Type is kUnknown_SkColorType or
pixel address is nullptr.

Color_Space in Image_Info is ignored. Some Color precision may be lost in the
conversion to Unpremultiplied Color; original pixel data may have additional 
precision.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  pixel converted to Unpremultiplied Color ##

#Example
    const int w = 4;
    const int h = 4;
    std::vector<SkPMColor> storage;
    storage.resize(w * h);
    SkDebugf("Premultiplied:\n");
    for (int y = 0; y < h; ++y) {
        SkDebugf("(0, %d) ", y);
        for (int x = 0; x < w; ++x) {
            int a = 0xFF * (x + y) / (w - 1 + h - 1);
            storage[x + y * w] = SkPackARGB32(a, a * x / (w - 1), a * y / (h - 1), a);
            SkDebugf("0x%08x%c", storage[x + y * w], x == w - 1 ? '\n' : ' ');
        }
    }
    SkPixmap pixmap(SkImageInfo::MakeN32(w, h, kPremul_SkAlphaType), &storage.front(), w * 4);
    SkDebugf("Unpremultiplied:\n");
    for (int y = 0; y < h; ++y) {
        SkDebugf("(0, %d) ", y);
        for (int x = 0; x < w; ++x) {
            SkDebugf("0x%08x%c", pixmap.getColor(x, y), x == w - 1 ? '\n' : ' ');
        }
    }
#StdOut
Premultiplied:
(0, 0) 0x00000000 0x2a0e002a 0x55380055 0x7f7f007f 
(0, 1) 0x2a000e2a 0x551c1c55 0x7f542a7f 0xaaaa38aa 
(0, 2) 0x55003855 0x7f2a547f 0xaa7171aa 0xd4d48dd4 
(0, 3) 0x7f007f7f 0xaa38aaaa 0xd48dd4d4 0xffffffff 
Unpremultiplied:
(0, 0) 0x00000000 0x2a5500ff 0x55a800ff 0x7fff00ff 
(0, 1) 0x2a0055ff 0x555454ff 0x7fa954ff 0xaaff54ff 
(0, 2) 0x5500a8ff 0x7f54a9ff 0xaaaaaaff 0xd4ffaaff 
(0, 3) 0x7f00ffff 0xaa54ffff 0xd4aaffff 0xffffffff 
##
##

#SeeAlso addr() readPixels

##

#Subtopic Reader ##

#Subtopic Readable_Address
#Line # returns read only pixels ##

# ------------------------------------------------------------------------------

#Method const void* addr(int x, int y) const

#In Readable_Address
Returns readable pixel address at (x, y). Returns nullptr if Pixel_Ref is nullptr.

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined. Returns nullptr if Color_Type is kUnknown_SkColorType.

Performs a lookup of pixel size; for better performance, call 
one of: addr8, addr16, addr32, addr64, or addrF16.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  readable generic pointer to pixel ##

#Example
    const int w = 4;
    const int h = 4;
    std::vector<SkPMColor> storage;
    storage.resize(w * h);
    SkPixmap pixmap(SkImageInfo::MakeN32(w, h, kPremul_SkAlphaType), &storage.front(), w * 4);
    SkDebugf("pixmap.addr(1, 2) %c= &storage[1 + 2 * w]\n",
              pixmap.addr(1, 2)  == &storage[1 + 2 * w] ? '=' : '!');
#StdOut
pixmap.addr(1, 2) == &storage[1 + 2 * w]
##
##

#SeeAlso addr8 addr16 addr32 addr64 addrF16 getColor writable_addr SkBitmap::getAddr

##

# ------------------------------------------------------------------------------

#Method const uint8_t* addr8() const 

#In Readable_Address
#Line # returns readable pixel address as 8-bit pointer ##
Returns readable base pixel address. Result is addressable as unsigned 8-bit bytes.
Will trigger an assert() if Color_Type is not kAlpha_8_SkColorType or
kGray_8_SkColorType, and is built with SK_DEBUG defined.

One byte corresponds to one pixel.

#Return  readable unsigned 8-bit pointer to pixels ##

#Example
    const int w = 4;
    const int h = 4;
    uint8_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kGray_8_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr8() %c= storage\n",
              pixmap.addr8()  == storage ? '=' : '!');
#StdOut
pixmap.addr8() == storage
##
##

#SeeAlso addr() addr16 addr32 addr64 addrF16 getColor writable_addr writable_addr8

##

# ------------------------------------------------------------------------------

#Method const uint16_t* addr16() const 

#In Readable_Address
#Line # returns readable pixel address as 16-bit pointer ##
Returns readable base pixel address. Result is addressable as unsigned 16-bit words.
Will trigger an assert() if Color_Type is not kRGB_565_SkColorType or
kARGB_4444_SkColorType, and is built with SK_DEBUG defined.

One word corresponds to one pixel.

#Return  readable unsigned 16-bit pointer to pixels ##

#Example
    const int w = 4;
    const int h = 4;
    uint16_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kARGB_4444_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr16() %c= storage\n",
              pixmap.addr16()  == storage ? '=' : '!');
#StdOut
pixmap.addr16() == storage
##
##

#SeeAlso addr() addr8 addr32 addr64 addrF16 getColor writable_addr writable_addr16

##

# ------------------------------------------------------------------------------

#Method const uint32_t* addr32() const 

#In Readable_Address
#Line # returns readable pixel address as 32-bit pointer ##
Returns readable base pixel address. Result is addressable as unsigned 32-bit words.
Will trigger an assert() if Color_Type is not kRGBA_8888_SkColorType or
kBGRA_8888_SkColorType, and is built with SK_DEBUG defined.

One word corresponds to one pixel.

#Return  readable unsigned 32-bit pointer to pixels ##

#Example
    const int w = 4;
    const int h = 4;
    uint32_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::MakeN32(w, h, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr32() %c= storage\n",
              pixmap.addr32()  == storage ? '=' : '!');
#StdOut
pixmap.addr32() == storage
##
##

#SeeAlso addr() addr8 addr16 addr64 addrF16 getColor writable_addr writable_addr32

##

# ------------------------------------------------------------------------------

#Method const uint64_t* addr64() const 

#In Readable_Address
#Line # returns readable pixel address as 64-bit pointer ##
Returns readable base pixel address. Result is addressable as unsigned 64-bit words.
Will trigger an assert() if Color_Type is not kRGBA_F16_SkColorType and is built
with SK_DEBUG defined.

One word corresponds to one pixel.

#Return  readable unsigned 64-bit pointer to pixels ##

#Example
    const int w = 4;
    const int h = 4;
    uint64_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kRGBA_F16_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr64() %c= storage\n",
              pixmap.addr64()  == storage ? '=' : '!');
#StdOut
pixmap.addr64() == storage
##
##

#SeeAlso addr() addr8 addr16 addr32 addrF16 getColor writable_addr writable_addr64

##

# ------------------------------------------------------------------------------

#Method const uint16_t* addrF16() const 

#In Readable_Address
#Line # returns readable pixel component address as 16-bit pointer ##
Returns readable base pixel address. Result is addressable as unsigned 16-bit words.
Will trigger an assert() if Color_Type is not kRGBA_F16_SkColorType and is built
with SK_DEBUG defined.

Each word represents one color component encoded as a half float.
Four words correspond to one pixel.

#Return  readable unsigned 16-bit pointer to first component of pixels ##

#Example
    const int w = 4;
    const int h = 4;
    uint16_t storage[w * h * 4];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kRGBA_F16_SkColorType, kPremul_SkAlphaType),
                    storage, w * 4 * sizeof(storage[0]));
    SkDebugf("pixmap.addrF16() %c= storage\n",
              pixmap.addrF16()  == storage ? '=' : '!');
#StdOut
pixmap.addrF16() == storage
##
##

#SeeAlso addr() addr8 addr16 addr32 addr64 getColor writable_addr writable_addrF16

##

# ------------------------------------------------------------------------------

#Method const uint8_t* addr8(int x, int y) const 

#In Readable_Address
Returns readable pixel address at (x, y).

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined.

Will trigger an assert() if Color_Type is not kAlpha_8_SkColorType or
kGray_8_SkColorType, and is built with SK_DEBUG defined.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  readable unsigned 8-bit pointer to pixel at (x, y) ##

#Example
    const int w = 4;
    const int h = 4;
    uint8_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kGray_8_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr8(1, 2) %c= &storage[1 + 2 * w]\n",
              pixmap.addr8(1, 2)  == &storage[1 + 2 * w] ? '=' : '!');
#StdOut
pixmap.addr8(1, 2) == &storage[1 + 2 * w]
##
##

#SeeAlso addr() addr16 addr32 addr64 addrF16 getColor writable_addr writable_addr8

##

# ------------------------------------------------------------------------------

#Method const uint16_t* addr16(int x, int y) const 

#In Readable_Address
Returns readable pixel address at (x, y).

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined.

Will trigger an assert() if Color_Type is not kRGB_565_SkColorType or
kARGB_4444_SkColorType, and is built with SK_DEBUG defined.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  readable unsigned 16-bit pointer to pixel at (x, y) ##

#Example
    const int w = 4;
    const int h = 4;
    uint16_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kARGB_4444_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr16(1, 2) %c= &storage[1 + 2 * w]\n",
              pixmap.addr16(1, 2)  == &storage[1 + 2 * w] ? '=' : '!');
#StdOut
pixmap.addr16(1, 2) == &storage[1 + 2 * w]
##
##

#SeeAlso addr() addr8 addr32 addr64 addrF16 getColor writable_addr writable_addr16

##

# ------------------------------------------------------------------------------

#Method const uint32_t* addr32(int x, int y) const 

#In Readable_Address
Returns readable pixel address at (x, y).

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined.

Will trigger an assert() if Color_Type is not kRGBA_8888_SkColorType or
kBGRA_8888_SkColorType, and is built with SK_DEBUG defined.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  readable unsigned 32-bit pointer to pixel at (x, y) ##

#Example
    const int w = 4;
    const int h = 4;
    uint32_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kRGBA_8888_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr32(1, 2) %c= &storage[1 + 2 * w]\n",
              pixmap.addr32(1, 2)  == &storage[1 + 2 * w] ? '=' : '!');
#StdOut
pixmap.addr32(1, 2) == &storage[1 + 2 * w]
##
##

#SeeAlso addr() addr8 addr16 addr64 addrF16 getColor writable_addr writable_addr64

##

# ------------------------------------------------------------------------------

#Method const uint64_t* addr64(int x, int y) const 

#In Readable_Address
Returns readable pixel address at (x, y).

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined.

Will trigger an assert() if Color_Type is not kRGBA_F16_SkColorType and is built
with SK_DEBUG defined.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  readable unsigned 64-bit pointer to pixel at (x, y) ##

#Example
    const int w = 4;
    const int h = 4;
    uint64_t storage[w * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kRGBA_F16_SkColorType, kPremul_SkAlphaType),
                    storage, w * sizeof(storage[0]));
    SkDebugf("pixmap.addr64(1, 2) %c= &storage[1 + 2 * w]\n",
              pixmap.addr64(1, 2)  == &storage[1 + 2 * w] ? '=' : '!');
#StdOut
pixmap.addr64(1, 2) == &storage[1 + 2 * w]
##
##

#SeeAlso addr() addr8 addr16 addr32 addrF16 getColor writable_addr writable_addr64

##

# ------------------------------------------------------------------------------

#Method const uint16_t* addrF16(int x, int y) const 

#In Readable_Address
Returns readable pixel address at (x, y).

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined.

Will trigger an assert() if Color_Type is not kRGBA_F16_SkColorType and is built
with SK_DEBUG defined.

Each unsigned 16-bit word represents one color component encoded as a half float.
Four words correspond to one pixel.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  readable unsigned 16-bit pointer to pixel component at (x, y) ##

#Example
    const int w = 4;
    const int h = 4;
    const int wordsPerPixel = 4;
    const int rowWords = w * wordsPerPixel;
    uint16_t storage[rowWords * h];
    SkPixmap pixmap(SkImageInfo::Make(w, h, kRGBA_F16_SkColorType, kPremul_SkAlphaType),
                    storage, rowWords * sizeof(storage[0]));
    SkDebugf("pixmap.addrF16(1, 2) %c= &storage[1 * wordsPerPixel + 2 * rowWords]\n",
              pixmap.addrF16(1, 2)  == &storage[1 * wordsPerPixel + 2 * rowWords] ? '=' : '!');
#StdOut
pixmap.addrF16(1, 2) == &storage[1 * wordsPerPixel + 2 * rowWords]
##
##

#SeeAlso addr() addr8 addr16 addr32 addr64 getColor writable_addr writable_addrF16

##

#Subtopic Readable_Address ##

#Subtopic Writable_Address
#Line # returns writable pixels ##

# ------------------------------------------------------------------------------

#Method void* writable_addr() const 

#In Writable_Address
#Line # returns writable pixel address as void pointer ##
Returns writable base pixel address.

#Return  writable generic base pointer to pixels ##

#Example
    const int w = 4;
    const int h = 4;
    SkPMColor storage[w * h * 4];
    SkPixmap pixmap(SkImageInfo::MakeN32(w, h, kPremul_SkAlphaType), storage, w * 4);
    SkDebugf("pixmap.writable_addr() %c= (void *)storage\n",
              pixmap.writable_addr()  == (void *)storage ? '=' : '!');
    pixmap.erase(0x00000000);
    *(SkPMColor*)pixmap.writable_addr() = 0xFFFFFFFF;
    SkDebugf("pixmap.getColor(0, 1) %c= 0x00000000\n",
              pixmap.getColor(0, 1)  == 0x00000000 ? '=' : '!');
    SkDebugf("pixmap.getColor(0, 0) %c= 0xFFFFFFFF\n",
              pixmap.getColor(0, 0)  == 0xFFFFFFFF ? '=' : '!');
#StdOut
pixmap.writable_addr() == (void *)storage
pixmap.getColor(0, 1) == 0x00000000
pixmap.getColor(0, 0) == 0xFFFFFFFF
##
##

#SeeAlso writable_addr8 writable_addr16 writable_addr32 writable_addr64 writable_addrF16 addr()

##

# ------------------------------------------------------------------------------

#Method void* writable_addr(int x, int y) const 

#In Writable_Address
Returns writable pixel address at (x, y).

Input is not validated: out of bounds values of x or y trigger an assert() if
built with SK_DEBUG defined. Returns zero if Color_Type is kUnknown_SkColorType.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  writable generic pointer to pixel ##

#Example
    const int w = 4;
    const int h = 4;
    SkPMColor storage[w * h * 4];
    SkPixmap pixmap(SkImageInfo::MakeN32(w, h, kPremul_SkAlphaType), storage, w * 4);
    SkDebugf("pixmap.writable_addr() %c= (void *)storage\n",
              pixmap.writable_addr()  == (void *)storage ? '=' : '!');
    pixmap.erase(0x00000000);
    *(SkPMColor*)pixmap.writable_addr(1, 2) = 0xFFFFFFFF;
    SkDebugf("pixmap.getColor(0, 0) %c= 0x00000000\n",
              pixmap.getColor(0, 0)  == 0x00000000 ? '=' : '!');
    SkDebugf("pixmap.getColor(1, 2) %c= 0xFFFFFFFF\n",
              pixmap.getColor(1, 2)  == 0xFFFFFFFF ? '=' : '!');
#StdOut
pixmap.writable_addr() == (void *)storage
pixmap.getColor(0, 0) == 0x00000000
pixmap.getColor(1, 2) == 0xFFFFFFFF
##
##

#SeeAlso writable_addr8 writable_addr16 writable_addr32 writable_addr64 writable_addrF16 addr()

##

# ------------------------------------------------------------------------------

#Method uint8_t* writable_addr8(int x, int y) const 

#In Writable_Address
#Line # returns writable pixel address as 8-bit pointer ##
Returns writable pixel address at (x, y). Result is addressable as unsigned
8-bit bytes. Will trigger an assert() if Color_Type is not kAlpha_8_SkColorType
or kGray_8_SkColorType, and is built with SK_DEBUG defined.

One byte corresponds to one pixel.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  writable unsigned 8-bit pointer to pixels ##

#Example
#Height 64
#Description
Altering pixels after drawing Bitmap is not guaranteed to affect subsequent
drawing on all platforms. Adding a second SkBitmap::installPixels after editing
pixel memory is safer.
##
void draw(SkCanvas* canvas) {
    uint8_t storage[][5] = {{ 0,   0,  64,   0,  0},
                            { 0, 128, 255, 128,  0},
                            {64, 255, 255, 255, 64},
                            { 0, 128, 255, 128,  0},
                            { 0,   0,  64,   0,  0}};
    SkImageInfo imageInfo = SkImageInfo::Make(5, 5, kGray_8_SkColorType, kPremul_SkAlphaType);
    SkPixmap pixmap(imageInfo, storage[0], 5);
    SkBitmap bitmap;
    bitmap.installPixels(pixmap);
    canvas->scale(10, 10);
    canvas->drawBitmap(bitmap, 0, 0);
    *pixmap.writable_addr8(2, 2) = 0;
//  bitmap.installPixels(pixmap);      // uncomment to fix on GPU
    canvas->drawBitmap(bitmap, 10, 0);
}
##

#SeeAlso writable_addr writable_addr16 writable_addr32 writable_addr64 writable_addrF16 addr() addr8

##

# ------------------------------------------------------------------------------

#Method uint16_t* writable_addr16(int x, int y) const 

#In Writable_Address
#Line # returns writable pixel address as 16-bit pointer ##
Returns writable_addr pixel address at (x, y). Result is addressable as unsigned
16-bit words. Will trigger an assert() if Color_Type is not kRGB_565_SkColorType
or kARGB_4444_SkColorType, and is built with SK_DEBUG defined.

One word corresponds to one pixel.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  writable unsigned 16-bit pointer to pixel ##

#Example
#Description
Draw a five by five bitmap, and draw it again with a center black pixel.
The low nibble of the 16-bit word is Alpha.
##
#Height 64
    uint16_t storage[][5] = {{ 0xCABF, 0xDABE, 0xCA9D, 0xC96C, 0xA39B },
                             { 0xACEE, 0xA87C, 0x893A, 0x4779, 0x8708 },
                             { 0x4B7C, 0x255B, 0x2559, 0x2557, 0x4656 },
                             { 0x9099, 0x8128, 0x2557, 0x4124, 0x3323 },
                             { 0x7547, 0x5505, 0x4434, 0x2012, 0x0000 }};
    SkImageInfo imageInfo = SkImageInfo::Make(5, 5, kARGB_4444_SkColorType, kPremul_SkAlphaType);
    SkPixmap pixmap(imageInfo, storage[0], sizeof(storage) / 5);
    SkBitmap bitmap;
    bitmap.installPixels(pixmap);
    canvas->scale(10, 10);
    canvas->drawBitmap(bitmap, 0, 0);
    *pixmap.writable_addr16(2, 2) = 0x000F;
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 10, 0);
##

#SeeAlso writable_addr writable_addr8 writable_addr32 writable_addr64 writable_addrF16 addr() addr16

##

# ------------------------------------------------------------------------------

#Method uint32_t* writable_addr32(int x, int y) const 

#In Writable_Address
#Line # returns writable pixel address as 32-bit pointer ##
Returns writable pixel address at (x, y). Result is addressable as unsigned
32-bit words. Will trigger an assert() if Color_Type is not
kRGBA_8888_SkColorType or kBGRA_8888_SkColorType, and is built with SK_DEBUG
defined.

One word corresponds to one pixel.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  writable unsigned 32-bit pointer to pixel ##

#Example
#Image 4
#Height 72
    std::vector<int32_t> pixels;
    pixels.resize(image->height() * image->width() * 4);
    SkPixmap pixmap(SkImageInfo::Make(image->width(), image->height(), kN32_SkColorType,
            image->alphaType()), (const void*) &pixels.front(), image->width() * 4);
    image->readPixels(pixmap, 0, 0);
    for (int y = 0; y < pixmap.height() / 2; ++y) {
        for (int x = 0; x < pixmap.width(); ++x) {
            if ((x & 4) == (y & 4)) {
                SkTSwap(*pixmap.writable_addr32(x, y), 
                        *pixmap.writable_addr32(pixmap.width() - x, pixmap.height() - y));
            }
        }
    }
    SkBitmap bitmap;
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 0, 0);
##

#SeeAlso writable_addr writable_addr8 writable_addr16 writable_addr64 writable_addrF16 addr() addr32

##

# ------------------------------------------------------------------------------

#Method uint64_t* writable_addr64(int x, int y) const 

#In Writable_Address
#Line # returns writable pixel address as 64-bit pointer ##
Returns writable pixel address at (x, y). Result is addressable as unsigned
64-bit words. Will trigger an assert() if Color_Type is not
kRGBA_F16_SkColorType and is built with SK_DEBUG defined.

One word corresponds to one pixel.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  writable unsigned 64-bit pointer to pixel ##

#Example
#Height 40
    SkImageInfo info = SkImageInfo::Make(3, 3, kRGBA_F16_SkColorType, kPremul_SkAlphaType);
    uint64_t storage[9];
    SkPixmap pixmap(info, storage, 3 * sizeof(uint64_t));
    SkColor4f c4 { 1, 0.45f, 0.25f, 0.65f };
    pixmap.erase(c4);
    SkBitmap bitmap;
    canvas->scale(10, 10);
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 0, 0);
    *pixmap.writable_addr64(1, 1) |= 0x00ff000000000000LL;
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 10, 0);
##

#SeeAlso writable_addr writable_addr8 writable_addr16 writable_addr32 writable_addrF16 addr() addr64

##

# ------------------------------------------------------------------------------

#Method uint16_t* writable_addrF16(int x, int y) const 

#In Writable_Address
#Line # returns writable pixel component address as 16-bit pointer ##
Returns writable pixel address at (x, y). Result is addressable as unsigned
16-bit words. Will trigger an assert() if Color_Type is not
kRGBA_F16_SkColorType and is built with SK_DEBUG defined.

Each word represents one color component encoded as a half float.
Four words correspond to one pixel.

#Param x  column index, zero or greater, and less than width() ##
#Param y  row index, zero or greater, and less than height() ##

#Return  writable unsigned 16-bit pointer to first component of pixel ##

#Example
#Height 64
#Description
Left bitmap is drawn with two pixels defined in half float format. Right bitmap
is drawn after overwriting bottom half float color with top half float color. 
##
    SkImageInfo info = SkImageInfo::Make(1, 2, kRGBA_F16_SkColorType, kPremul_SkAlphaType);
    uint16_t storage[2][4];
    SkPixmap pixmap(info, storage[0], sizeof(uint64_t));
    SkIRect topPixelBounds = {0, 0, 1, 1};
    pixmap.erase({ 0.65f, 0.45f, 0.25f, 1 }, &topPixelBounds);
    SkIRect bottomPixelBounds = {0, 1, 1, 2};
    pixmap.erase({ 0.25f, 0.65f, 0.45f, 1 }, &bottomPixelBounds);
    SkBitmap bitmap;
    canvas->scale(20, 20);
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 0, 0);
    uint16_t* pixel2 = pixmap.writable_addrF16(0, 1);
    for (int i = 0; i < 4; ++i) {
        pixel2[i] = storage[0][i];
    }
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 4, 0);
##

#SeeAlso writable_addr writable_addr8 writable_addr16 writable_addr32 writable_addr64 addr() addrF16

##

#Subtopic Writable_Address ##

#Subtopic Pixels
#Populate
#Line # read and write pixel values ##
##

# ------------------------------------------------------------------------------

#Method bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes,
                    int srcX, int srcY, SkTransferFunctionBehavior behavior) const
#In Pixels
#Line # copies and converts pixels ##

Copies a Rect of pixels to dstPixels. Copy starts at (srcX, srcY), and does not
exceed Pixmap (width(), height()). 

dstInfo specifies width, height, Color_Type, Alpha_Type, and 
Color_Space of destination. dstRowBytes specifics the gap from one destination
row to the next. Returns true if pixels are copied. Returns false if
dstInfo.addr() equals nullptr, or dstRowBytes is less than dstInfo.minRowBytes.

Pixels are copied only if pixel conversion is possible. If Pixmap colorType is
kGray_8_SkColorType, or kAlpha_8_SkColorType; dstInfo.colorType must match.
If Pixmap colorType is kGray_8_SkColorType, dstInfo.colorSpace must match.
If Pixmap alphaType is kOpaque_SkAlphaType, dstInfo.alphaType must
match. If Pixmap colorSpace is nullptr, dstInfo.colorSpace must match. Returns
false if pixel conversion is not possible.
 
srcX and srcY may be negative to copy only top or left of source. Returns
false if width() or height() is zero or negative. Returns false if:

#Formula
abs(srcX) >= Pixmap width()
##
, or if
#Formula
abs(srcY) >= Pixmap height()
##
.

If behavior is SkTransferFunctionBehavior::kRespect: converts source
pixels to a linear space before converting to dstInfo.
If behavior is SkTransferFunctionBehavior::kIgnore: source
pixels are treated as if they are linear, regardless of how they are encoded.

#Param dstInfo  destination width, height, Color_Type, Alpha_Type, Color_Space ##
#Param dstPixels  destination pixel storage ##
#Param dstRowBytes  destination row length ##
#Param srcX  column index whose absolute value is less than width() ##
#Param srcY  row index whose absolute value is less than height() ##
#Param behavior  one of: SkTransferFunctionBehavior::kRespect,
                         SkTransferFunctionBehavior::kIgnore 
##

#Return  true if pixels are copied to dstPixels ##

#Example
#ToDo example doesn't do anything interesting since info colorSpace is nullptr ##
#Image 3
void draw(SkCanvas* canvas) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(image->width(), image->height(),
            canvas->imageInfo().colorSpace() ? SkColorSpace::MakeSRGB() : nullptr);
    std::vector<int32_t> srcPixels;
    srcPixels.resize(image->height() * image->width() * 4);
    SkPixmap pixmap(info, (const void*) &srcPixels.front(), image->width() * 4);
    image->readPixels(pixmap, 0, 0);
    SkTransferFunctionBehavior behavior = canvas->imageInfo().colorSpace() ?
            SkTransferFunctionBehavior::kRespect : SkTransferFunctionBehavior::kIgnore;
    std::vector<int32_t> dstPixels;
    dstPixels.resize(image->height() * image->width() * 4);
    int offset = 0;
    for (auto behavior : { SkTransferFunctionBehavior::kRespect,
                           SkTransferFunctionBehavior::kIgnore} ) {
        pixmap.readPixels(info, &dstPixels.front(), image->width() * 4, offset, 0, behavior);
        offset += 128;
    }
    SkBitmap bitmap;
    SkPixmap dstmap(info, &dstPixels.front(), image->width() * 4);
    bitmap.installPixels(dstmap);
    canvas->drawBitmap(bitmap, 0, 0);
}
##

#SeeAlso erase SkBitmap::readPixels SkCanvas::drawBitmap SkCanvas::readPixels SkImage::readPixels SkSurface::readPixels

##

# ------------------------------------------------------------------------------

#Method bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes) const 

#In Pixels
Copies a Rect of pixels to dstPixels. Copy starts at (0, 0), and does not
exceed Pixmap (width(), height()).

dstInfo specifies width, height, Color_Type, Alpha_Type, and 
Color_Space of destination. dstRowBytes specifics the gap from one destination
row to the next. Returns true if pixels are copied. Returns false if
dstInfo.addr() equals nullptr, or dstRowBytes is less than dstInfo.minRowBytes.

Pixels are copied only if pixel conversion is possible. If Pixmap colorType is
kGray_8_SkColorType, or kAlpha_8_SkColorType; dstInfo.colorType must match.
If Pixmap colorType is kGray_8_SkColorType, dstInfo.colorSpace must match.
If Pixmap alphaType is kOpaque_SkAlphaType, dstInfo.alphaType must
match. If Pixmap colorSpace is nullptr, dstInfo.colorSpace must match. Returns
false if pixel conversion is not possible.

Returns false if Pixmap width() or height() is zero or negative.

#Param dstInfo  destination width, height, Color_Type, Alpha_Type, Color_Space ##
#Param dstPixels  destination pixel storage ##
#Param dstRowBytes  destination row length ##

#Return  true if pixels are copied to dstPixels ##

#Example
#Height 128
#Description
Transferring the gradient from 8 bits per component to 4 bits per component
creates visible banding.
##
    std::vector<int32_t> pixels;
    const int width = 256;
    const int height = 64;
    pixels.resize(height * width * 4);
    SkImageInfo srcInfo = SkImageInfo::MakeN32Premul(width, height);
    SkPixmap srcPixmap(srcInfo, (const void*) &pixels.front(), width * 4);
    SkColor  gradColors[] = { 0xFFAA3300, 0x7F881122 };
    SkPoint  gradPoints[] = { { 0, 0 }, { 256, 0 } };
    SkPaint paint;
    paint.setShader(SkGradientShader::MakeLinear(gradPoints, gradColors, nullptr,
                    SK_ARRAY_COUNT(gradColors), SkShader::kClamp_TileMode));
    SkBitmap bitmap;
    bitmap.installPixels(srcPixmap);
    SkCanvas srcCanvas(bitmap);
    srcCanvas.drawRect(SkRect::MakeWH(width, height), paint);
    canvas->drawBitmap(bitmap, 0, 0);
    std::vector<int32_t> dstPixels;
    dstPixels.resize(height * width * 2);
    SkImageInfo dstInfo = srcInfo.makeColorType(kARGB_4444_SkColorType);
    srcPixmap.readPixels(dstInfo, &dstPixels.front(), width * 2);
    SkPixmap dstPixmap(dstInfo, &dstPixels.front(), width * 2);
    bitmap.installPixels(dstPixmap);
    canvas->drawBitmap(bitmap, 0, 128);
##

#SeeAlso erase SkBitmap::readPixels SkCanvas::drawBitmap SkCanvas::readPixels SkImage::readPixels SkSurface::readPixels

##

# ------------------------------------------------------------------------------

#Method bool readPixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRowBytes, int srcX,
                    int srcY) const 

Copies a Rect of pixels to dstPixels. Copy starts at (srcX, srcY), and does not
exceed Pixmap (width(), height()).

dstInfo specifies width, height, Color_Type, Alpha_Type, and 
Color_Space of destination. dstRowBytes specifics the gap from one destination
row to the next. Returns true if pixels are copied. Returns false if
dstInfo.addr() equals nullptr, or dstRowBytes is less than dstInfo.minRowBytes.

Pixels are copied only if pixel conversion is possible. If Pixmap colorType is
kGray_8_SkColorType, or kAlpha_8_SkColorType; dstInfo.colorType must match.
If Pixmap colorType is kGray_8_SkColorType, dstInfo.colorSpace must match.
If Pixmap alphaType is kOpaque_SkAlphaType, dstInfo.alphaType must
match. If Pixmap colorSpace is nullptr, dstInfo.colorSpace must match. Returns
false if pixel conversion is not possible.
 
srcX and srcY may be negative to copy only top or left of source. Returns
false if Pixmap width() or height() is zero or negative. Returns false if:

#Formula
abs(srcX) >= Pixmap width()
##
, or if
#Formula
abs(srcY) >= Pixmap height()
##
.

#Param dstInfo  destination width, height, Color_Type, Alpha_Type, Color_Space ##
#Param dstPixels  destination pixel storage ##
#Param dstRowBytes  destination row length ##
#Param srcX  column index whose absolute value is less than width() ##
#Param srcY  row index whose absolute value is less than height() ##

#Return  true if pixels are copied to dstPixels ##

#Example
#Image 3
void draw(SkCanvas* canvas) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(image->width(), image->height());
    std::vector<int32_t> srcPixels;
    const int rowBytes = image->width() * 4;
    srcPixels.resize(image->height() * rowBytes);
    SkPixmap pixmap(info, (const void*) &srcPixels.front(), rowBytes);
    image->readPixels(pixmap, 0, 0);
    for (int offset : { 32, 64, 96 } ) {
        std::vector<int32_t> dstPixels;
        dstPixels.resize(image->height() * rowBytes);
        pixmap.readPixels(info, &dstPixels.front(), rowBytes, offset, 0);
        SkBitmap bitmap;
        SkPixmap dstmap(info, &dstPixels.front(), rowBytes);
        bitmap.installPixels(dstmap);
        canvas->translate(32, 32);
        canvas->drawBitmap(bitmap, 0, 0);
    }
}
##

#SeeAlso erase SkBitmap::readPixels SkCanvas::drawBitmap SkCanvas::readPixels SkImage::readPixels SkSurface::readPixels

##

# ------------------------------------------------------------------------------

#Method bool readPixels(const SkPixmap& dst, int srcX, int srcY) const 

Copies a Rect of pixels to dst. Copy starts at (srcX, srcY), and does not
exceed Pixmap (width(), height()). dst specifies width, height, Color_Type,
Alpha_Type, and Color_Space of destination.  Returns true if pixels are copied.
Returns false if dst.addr() equals nullptr, or dst.rowBytes is less than
dst SkImageInfo::minRowBytes.

Pixels are copied only if pixel conversion is possible. If Pixmap colorType is
kGray_8_SkColorType, or kAlpha_8_SkColorType; dst.info().colorType must match.
If Pixmap colorType is kGray_8_SkColorType, dst.info().colorSpace must match.
If Pixmap alphaType is kOpaque_SkAlphaType, dst.info().alphaType must
match. If Pixmap colorSpace is nullptr, dst.info().colorSpace must match. Returns
false if pixel conversion is not possible.
 
srcX and srcY may be negative to copy only top or left of source. Returns
false Pixmap width() or height() is zero or negative. Returns false if:

#Formula
abs(srcX) >= Pixmap width()
##
, or if
#Formula
abs(srcY) >= Pixmap height()
##
.

#Param dst  Image_Info and pixel address to write to ##
#Param srcX  column index whose absolute value is less than width() ##
#Param srcY  row index whose absolute value is less than height() ##

#Return  true if pixels are copied to dst ##

#Example
#Image 3
void draw(SkCanvas* canvas) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(image->width(), image->height());
    std::vector<int32_t> srcPixels;
    const int rowBytes = image->width() * 4;
    srcPixels.resize(image->height() * rowBytes);
    SkPixmap pixmap(info, (const void*) &srcPixels.front(), rowBytes);
    image->readPixels(pixmap, 0, 0);
    for (int offset : { 32, 64, 96 } ) {
        std::vector<int32_t> dstPixels;
        dstPixels.resize(image->height() * rowBytes);
        SkPixmap dstmap(info, &dstPixels.front(), rowBytes);
        pixmap.readPixels(dstmap, offset, 0);
        SkBitmap bitmap;
        bitmap.installPixels(dstmap);
        canvas->translate(32, 32);
        canvas->drawBitmap(bitmap, 0, 0);
    }
}
##

#SeeAlso erase SkBitmap::readPixels SkCanvas::drawBitmap SkCanvas::readPixels SkImage::readPixels SkSurface::readPixels

##

# ------------------------------------------------------------------------------

#Method bool readPixels(const SkPixmap& dst) const 

Copies pixels inside bounds() to dst. dst specifies width, height, Color_Type,
Alpha_Type, and Color_Space of destination.  Returns true if pixels are copied.
Returns false if dst.addr() equals nullptr, or dst.rowBytes is less than
dst SkImageInfo::minRowBytes.

Pixels are copied only if pixel conversion is possible. If Pixmap colorType is
kGray_8_SkColorType, or kAlpha_8_SkColorType; dst Color_Type must match.
If Pixmap colorType is kGray_8_SkColorType, dst Color_Space must match.
If Pixmap alphaType is kOpaque_SkAlphaType, dst Alpha_Type must
match. If Pixmap colorSpace is nullptr, dst Color_Space must match. Returns
false if pixel conversion is not possible.
 
Returns false if Pixmap width() or height() is zero or negative.

#Param dst  Image_Info and pixel address to write to ##

#Return  true if pixels are copied to dst ##

#Example
#Image 3
void draw(SkCanvas* canvas) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(image->width(), image->height());
    std::vector<int32_t> srcPixels;
    const int rowBytes = image->width() * 4;
    srcPixels.resize(image->height() * rowBytes);
    SkPixmap pixmap(info, (const void*) &srcPixels.front(), rowBytes);
    image->readPixels(pixmap, 0, 0);
    for (int index = 0; index < 3; ++index ) {
        std::vector<int32_t> dstPixels;
        dstPixels.resize(image->height() * rowBytes);
        SkPixmap dstmap(info, &dstPixels.front(), rowBytes);
        pixmap.readPixels(dstmap);
        SkBitmap bitmap;
        bitmap.installPixels(dstmap);
        canvas->translate(32, 32);
        canvas->drawBitmap(bitmap, 0, 0);
    }
}
##

#SeeAlso erase SkBitmap::readPixels SkCanvas::drawBitmap SkCanvas::readPixels SkImage::readPixels SkSurface::readPixels

##

# ------------------------------------------------------------------------------

#Method bool scalePixels(const SkPixmap& dst, SkFilterQuality filterQuality) const

#In Pixels
#Line # scales and converts pixels ##
Copies Bitmap to dst, scaling pixels to fit dst.width() and dst.height(), and
converting pixels to match dst.colorType and dst.alphaType. Returns true if
pixels are copied. Returns false if dst.addr() is nullptr, or dst.rowBytes is
less than dst SkImageInfo::minRowBytes.

Pixels are copied only if pixel conversion is possible. If Pixmap colorType is
kGray_8_SkColorType, or kAlpha_8_SkColorType; dst Color_Type must match.
If Pixmap colorType is kGray_8_SkColorType, dst Color_Space must match.
If Pixmap alphaType is kOpaque_SkAlphaType, dst Alpha_Type must
match. If Pixmap colorSpace is nullptr, dst Color_Space must match. Returns
false if pixel conversion is not possible.

Returns false if Bitmap width() or height() is zero or negative.

Scales the image, with filterQuality, to match dst.width() and dst.height().
filterQuality kNone_SkFilterQuality is fastest, typically implemented with
Filter_Quality_Nearest_Neighbor. kLow_SkFilterQuality is typically implemented with
Filter_Quality_Bilerp. kMedium_SkFilterQuality is typically implemented with
Filter_Quality_Bilerp, and Filter_Quality_MipMap when size is reduced.
kHigh_SkFilterQuality is slowest, typically implemented with Filter_Quality_BiCubic.

#Param dst  Image_Info and pixel address to write to ##
#Param filterQuality  one of: kNone_SkFilterQuality, kLow_SkFilterQuality, 
                      kMedium_SkFilterQuality, kHigh_SkFilterQuality
##

#Return  true if pixels are scaled to fit dst ##

#Example
#Image 3
void draw(SkCanvas* canvas) {
    SkImageInfo info = SkImageInfo::MakeN32Premul(image->width(), image->height());
    std::vector<int32_t> srcPixels;
    int rowBytes = image->width() * 4;
    srcPixels.resize(image->height() * rowBytes);
    SkPixmap pixmap(info, (const void*) &srcPixels.front(), rowBytes);
    image->readPixels(pixmap, 0, 0);
    for (int offset : { 32, 64, 96 } ) {
        info = SkImageInfo::MakeN32Premul(image->width() + offset, image->height());
        rowBytes = info.width() * 4;
        std::vector<int32_t> dstPixels;
        dstPixels.resize(image->height() * rowBytes);
        SkPixmap dstmap(info, &dstPixels.front(), rowBytes);
        pixmap.scalePixels(dstmap, kMedium_SkFilterQuality);
        SkBitmap bitmap;
        bitmap.installPixels(dstmap);
        canvas->translate(32, 32);
        canvas->drawBitmap(bitmap, 0, 0);
    }
}
##

#SeeAlso SkCanvas::drawBitmap SkImage::scalePixels

##

# ------------------------------------------------------------------------------

#Method bool erase(SkColor color, const SkIRect& subset) const

#In Pixels
#Line # writes Color to pixels ##
Writes color to pixels bounded by subset; returns true on success.
Returns false if colorType is kUnknown_SkColorType, or if subset does
not intersect bounds().
  
#Param color  Unpremultiplied Color to write ##
#Param subset bounding integer Rect of written pixels ##

#Return  true if pixels are changed ##

#Example
#Height 50
    uint32_t storage[2];
    SkImageInfo info = SkImageInfo::MakeN32Premul(1, 2);
    SkPixmap pixmap(info, storage, info.minRowBytes());
    pixmap.erase(SK_ColorBLUE, {0, 0, 1, 1});
    pixmap.erase(SK_ColorRED, {0, 1, 1, 2});
    SkBitmap bitmap;
    canvas->scale(20, 20);
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 0, 0);
##

#SeeAlso SkBitmap::erase SkCanvas::clear SkCanvas::drawColor

##

# ------------------------------------------------------------------------------

#Method bool erase(SkColor color) const 

Writes color to pixels inside bounds(); returns true on success.
Returns false if colorType is kUnknown_SkColorType, or if bounds()
is empty.

#Param color  Unpremultiplied Color to write ##

#Return  true if pixels are changed ##

#Example
#Height 50
    uint32_t storage[2];
    SkImageInfo info = SkImageInfo::MakeN32Premul(1, 2);
    SkPixmap pixmap(info, storage, info.minRowBytes());
    pixmap.erase(SK_ColorBLUE);
    SkBitmap bitmap;
    canvas->scale(20, 20);
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 0, 0);
##

#SeeAlso SkBitmap::erase SkCanvas::clear SkCanvas::drawColor

##

# ------------------------------------------------------------------------------

#Method bool erase(const SkColor4f& color, const SkIRect* subset = nullptr) const

Writes color to pixels bounded by subset; returns true on success.
if subset is nullptr, writes colors pixels inside bounds(). Returns false if
colorType is kUnknown_SkColorType, if subset is not nullptr and does
not intersect bounds(), or if subset is nullptr and bounds() is empty.

#Param color  Unpremultiplied Color to write ##
#Param subset  bounding integer Rect of pixels to write; may be nullptr ##

#Return  true if pixels are changed ##

#Example
#Height 50
    uint32_t storage[2];
    SkImageInfo info = SkImageInfo::MakeN32Premul(1, 2);
    SkPixmap pixmap(info, storage, info.minRowBytes());
    SkIRect topPixelBounds = {0, 0, 1, 1};
    pixmap.erase({ 0.65f, 0.45f, 0.25f, 1 }, &topPixelBounds);
    SkIRect bottomPixelBounds = {0, 1, 1, 2};
    pixmap.erase({ 0.25f, 0.65f, 0.45f, 1 }, &bottomPixelBounds);
    SkBitmap bitmap;
    canvas->scale(20, 20);
    bitmap.installPixels(pixmap);
    canvas->drawBitmap(bitmap, 0, 0);
##

#SeeAlso SkBitmap::erase SkCanvas::clear SkCanvas::drawColor

##

#Class SkPixmap ##

#Topic Pixmap ##