Support more swizzles to 565 in SkCodec

Add more swizzling functions for swizzling to 565. Much of this
code was revived from crrev.com/1055743003 (for BMP). Also added
swizzling functions for WBMP.

Consolidate the static function conversion_possible.

In SkCodec::getPixels, check that the alphatype corresponds to the
colorType. This prevents requesting 565 + non-opaque.

In SkIcoCodec, report that the image is unpremul (instead of
whatever the largest embedded codec thinks), but modify the
requested info to have the alpha type expected/required by the
embedded codec.

Add tests for decoding to 565.

BUG=skia:3257
BUG=skia:3683

Review URL: https://codereview.chromium.org/1277213002

1 files changed, 73 insertions, 0 deletions

diff --git a/src/codec/SkSwizzler.cpp b/src/codec/SkSwizzler.cpp
index 44277614c6..8315cc7145 100644
--- a/src/codec/SkSwizzler.cpp
+++ b/src/codec/SkSwizzler.cpp
@@ -114,6 +114,34 @@ static SkSwizzler::ResultAlpha swizzle_bit_to_n32(
     return SkSwizzler::kOpaque_ResultAlpha;
 }
 
+#define RGB565_BLACK 0
+#define RGB565_WHITE 0xFFFF
+
+static SkSwizzler::ResultAlpha swizzle_bit_to_565(
+        void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int dstWidth,
+        int deltaSrc, int offset, const SkPMColor* /*ctable*/) {
+    uint16_t* SK_RESTRICT dst = (uint16_t*) dstRow;
+
+    // increment src by byte offset and bitIndex by bit offset
+    src += offset / 8;
+    int bitIndex = offset % 8;
+    uint8_t currByte = *src;
+
+    dst[0] = ((currByte >> (7 - bitIndex)) & 1) ? RGB565_WHITE : RGB565_BLACK;
+
+    for (int x = 1; x < dstWidth; x++) {
+        int bitOffset = bitIndex + deltaSrc;
+        bitIndex = bitOffset % 8;
+        currByte = *(src += bitOffset / 8);
+        dst[x] = ((currByte >> (7 - bitIndex)) & 1) ? RGB565_WHITE : RGB565_BLACK;
+    }
+
+    return SkSwizzler::kOpaque_ResultAlpha;
+}
+
+#undef RGB565_BLACK
+#undef RGB565_WHITE
+
 // kIndex1, kIndex2, kIndex4
 
 static SkSwizzler::ResultAlpha swizzle_small_index_to_index(
@@ -140,6 +168,29 @@ static SkSwizzler::ResultAlpha swizzle_small_index_to_index(
     return COMPUTE_RESULT_ALPHA;
 }
 
+static SkSwizzler::ResultAlpha swizzle_small_index_to_565(
+        void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int dstWidth,
+        int bitsPerPixel, int offset, const SkPMColor ctable[]) {
+
+    src += offset;
+    uint16_t* SK_RESTRICT dst = (uint16_t*) dstRow;
+    const uint32_t pixelsPerByte = 8 / bitsPerPixel;
+    const size_t rowBytes = compute_row_bytes_ppb(dstWidth, pixelsPerByte);
+    const uint8_t mask = (1 << bitsPerPixel) - 1;
+    int x = 0;
+    for (uint32_t byte = 0; byte < rowBytes; byte++) {
+        uint8_t pixelData = src[byte];
+        for (uint32_t p = 0; p < pixelsPerByte && x < dstWidth; p++) {
+            uint8_t index = (pixelData >> (8 - bitsPerPixel)) & mask;
+            uint16_t c = SkPixel32ToPixel16(ctable[index]);
+            dst[x] = c;
+            pixelData <<= bitsPerPixel;
+            x++;
+        }
+    }
+    return SkSwizzler::kOpaque_ResultAlpha;
+}
+
 static SkSwizzler::ResultAlpha swizzle_small_index_to_n32(
         void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int dstWidth,
         int bitsPerPixel, int offset, const SkPMColor ctable[]) {
@@ -306,6 +357,19 @@ static SkSwizzler::ResultAlpha swizzle_bgrx_to_n32(
     return SkSwizzler::kOpaque_ResultAlpha;
 }
 
+static SkSwizzler::ResultAlpha swizzle_bgrx_to_565(
+        void* SK_RESTRICT dstRow, const uint8_t* SK_RESTRICT src, int dstWidth,
+        int deltaSrc, int offset, const SkPMColor ctable[]) {
+    // FIXME: Support dithering?
+    src += offset;
+    uint16_t* SK_RESTRICT dst = (uint16_t*)dstRow;
+    for (int x = 0; x < dstWidth; x++) {
+        dst[x] = SkPack888ToRGB16(src[2], src[1], src[0]);
+        src += deltaSrc;
+    }
+    return SkSwizzler::kOpaque_ResultAlpha;
+}
+
 // kBGRA
 
 static SkSwizzler::ResultAlpha swizzle_bgra_to_n32_unpremul(
@@ -470,6 +534,9 @@ SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc,
                 case kIndex_8_SkColorType:
                     proc = &swizzle_bit_to_index;
                     break;
+                case kRGB_565_SkColorType:
+                    proc = &swizzle_bit_to_565;
+                    break;
                 case kGray_8_SkColorType:
                     proc = &swizzle_bit_to_grayscale;
                     break;
@@ -484,6 +551,9 @@ SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc,
                 case kN32_SkColorType:
                     proc = &swizzle_small_index_to_n32;
                     break;
+                case kRGB_565_SkColorType:
+                    proc = &swizzle_small_index_to_565;
+                    break;
                 case kIndex_8_SkColorType:
                     proc = &swizzle_small_index_to_index;
                     break;
@@ -534,6 +604,9 @@ SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc,
                 case kN32_SkColorType:
                     proc = &swizzle_bgrx_to_n32;
                     break;
+                case kRGB_565_SkColorType:
+                    proc = &swizzle_bgrx_to_565;
+                    break;
                 default:
                     break;
             }