Repeating SkBitmapProcState rounding bias

Observe the bias in repeat matrix procs also.

Introduce a utility class to handle device space -> bitmap space
mapping.

BUG=skia:4680,skia:4649
R=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1529833003

Review URL: https://codereview.chromium.org/1529833003

1 files changed, 7 insertions, 13 deletions

diff --git a/src/core/SkBitmapProcState_matrix_template.h b/src/core/SkBitmapProcState_matrix_template.h
index 468013c30d..9d639b8a04 100644
--- a/src/core/SkBitmapProcState_matrix_template.h
+++ b/src/core/SkBitmapProcState_matrix_template.h
@@ -22,13 +22,10 @@ void NoFilterProc_Scale(const SkBitmapProcState& s, uint32_t xy[],
     const unsigned maxX = s.fPixmap.width() - 1;
     SkFractionalInt fx;
     {
-        SkPoint pt;
-        s.fInvProc(s.fInvMatrix, SkIntToScalar(x) + SK_ScalarHalf,
-                                  SkIntToScalar(y) + SK_ScalarHalf, &pt);
-        fx = SkScalarToFractionalInt(pt.fY);
+        const SkBitmapProcStateAutoMapper mapper(s, x ,y);
         const unsigned maxY = s.fPixmap.height() - 1;
-        *xy++ = TileProc::Y(s, SkFractionalIntToFixed(fx), maxY);
-        fx = SkScalarToFractionalInt(pt.fX);
+        *xy++ = TileProc::Y(s, mapper.y(), maxY);
+        fx = SkFixedToFractionalInt(mapper.x());
     }
 
     if (0 == maxX) {
@@ -80,13 +77,9 @@ void NoFilterProc_Affine(const SkBitmapProcState& s, uint32_t xy[],
                              SkMatrix::kScale_Mask |
                              SkMatrix::kAffine_Mask)) == 0);
 
-    SkPoint srcPt;
-    s.fInvProc(s.fInvMatrix,
-               SkIntToScalar(x) + SK_ScalarHalf,
-               SkIntToScalar(y) + SK_ScalarHalf, &srcPt);
-
-    SkFractionalInt fx = SkScalarToFractionalInt(srcPt.fX);
-    SkFractionalInt fy = SkScalarToFractionalInt(srcPt.fY);
+    const SkBitmapProcStateAutoMapper mapper(s, x ,y);
+    SkFractionalInt fx = SkFixedToFractionalInt(mapper.x());
+    SkFractionalInt fy = SkFixedToFractionalInt(mapper.y());
     SkFractionalInt dx = s.fInvSxFractionalInt;
     SkFractionalInt dy = s.fInvKyFractionalInt;
     int maxX = s.fPixmap.width() - 1;
@@ -107,6 +100,7 @@ void NoFilterProc_Persp(const SkBitmapProcState& s, uint32_t* SK_RESTRICT xy,
     int maxX = s.fPixmap.width() - 1;
     int maxY = s.fPixmap.height() - 1;
 
+    // TODO: inv bias support
     SkPerspIter   iter(s.fInvMatrix,
                        SkIntToScalar(x) + SK_ScalarHalf,
                        SkIntToScalar(y) + SK_ScalarHalf, count);