Support RGBA/BGRA swizzles using SkEncodedInfo

src/codec/SkPngCodec.cpp

Index: src/codec/SkPngCodec.cpp
diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp
index ed6de7dbd0cae9e3812f2d226737a9f1dfcd289d..ba703146ebacfa905ede816fba8e05c6e8f3705a 100644
--- a/src/codec/SkPngCodec.cpp
+++ b/src/codec/SkPngCodec.cpp
@@ -86,14 +86,10 @@ private:
 };
 #define AutoCleanPng(...) SK_REQUIRE_LOCAL_VAR(AutoCleanPng)
 
-// Method for coverting to either an SkPMColor or a similarly packed
-// unpremultiplied color.
-typedef uint32_t (*PackColorProc)(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
-
 // Note: SkColorTable claims to store SkPMColors, which is not necessarily
 // the case here.
 // TODO: If we add support for non-native swizzles, we'll need to handle that here.
-bool SkPngCodec::decodePalette(bool premultiply, int* ctableCount) {
+bool SkPngCodec::decodePalette(bool premultiply, SkColorType dstColorType, int* ctableCount) {
 
     int numColors;
     png_color* palette;
@@ -109,12 +105,7 @@ bool SkPngCodec::decodePalette(bool premultiply, int* ctableCount) {
     if (png_get_tRNS(fPng_ptr, fInfo_ptr, &alphas, &numColorsWithAlpha, nullptr)) {
         // Choose which function to use to create the color table. If the final destination's
         // colortype is unpremultiplied, the color table will store unpremultiplied colors.
-        PackColorProc proc;
-        if (premultiply) {
-            proc = &SkPremultiplyARGBInline;
-        } else {
-            proc = &SkPackARGB32NoCheck;
-        }
+        PackColorProc proc = choose_pack_color_proc(premultiply, dstColorType);
 
         for (int i = 0; i < numColorsWithAlpha; i++) {
             // We don't have a function in SkOpts that combines a set of alphas with a set
@@ -134,11 +125,13 @@ bool SkPngCodec::decodePalette(bool premultiply, int* ctableCount) {
         SkASSERT(&palette->green < &palette->blue);
 #endif
 
-#ifdef SK_PMCOLOR_IS_RGBA
-        SkOpts::RGB_to_RGB1(colorPtr + numColorsWithAlpha, palette, numColors - numColorsWithAlpha);
-#else
-        SkOpts::RGB_to_BGR1(colorPtr + numColorsWithAlpha, palette, numColors - numColorsWithAlpha);
-#endif
+        if (is_rgba(dstColorType)) {
+            SkOpts::RGB_to_RGB1(colorPtr + numColorsWithAlpha, palette,
+                    numColors - numColorsWithAlpha);
+        } else {
+            SkOpts::RGB_to_BGR1(colorPtr + numColorsWithAlpha, palette,
+                    numColors - numColorsWithAlpha);
+        }
     }
 
     // Pad the color table with the last color in the table (or black) in the case that
@@ -425,7 +418,6 @@ SkPngCodec::SkPngCodec(const SkEncodedInfo& info, SkStream* stream, SkPngChunkRe
     , fPngChunkReader(SkSafeRef(chunkReader))
     , fPng_ptr(png_ptr)
     , fInfo_ptr(info_ptr)
-    , fSrcConfig(SkSwizzler::kUnknown)
     , fNumberPasses(numberPasses)
     , fBitDepth(bitDepth)
 {}
@@ -460,45 +452,11 @@ SkCodec::Result SkPngCodec::initializeSwizzler(const SkImageInfo& requestedInfo,
     }
     png_read_update_info(fPng_ptr, fInfo_ptr);
 
-    // suggestedColorType was determined in read_header() based on the encodedColorType
-    const SkColorType suggestedColorType = this->getInfo().colorType();
-
-    switch (suggestedColorType) {
-        case kIndex_8_SkColorType:
-            //decode palette to Skia format
-            fSrcConfig = SkSwizzler::kIndex;
-            if (!this->decodePalette(kPremul_SkAlphaType == requestedInfo.alphaType(),
-                    ctableCount)) {
-                return kInvalidInput;
-            }
-            break;
-        case kGray_8_SkColorType:
-            fSrcConfig = SkSwizzler::kGray;
-            break;
-        case kN32_SkColorType: {
-            const uint8_t encodedColorType = png_get_color_type(fPng_ptr, fInfo_ptr);
-            if (PNG_COLOR_TYPE_GRAY_ALPHA == encodedColorType ||
-                    PNG_COLOR_TYPE_GRAY == encodedColorType) {
-                // If encodedColorType is GRAY, there must be a transparent chunk.
-                // Otherwise, suggestedColorType would be kGray.  We have already
-                // instructed libpng to convert the transparent chunk to alpha,
-                // so we can treat both GRAY and GRAY_ALPHA as kGrayAlpha.
-                SkASSERT(encodedColorType == PNG_COLOR_TYPE_GRAY_ALPHA ||
-                        png_get_valid(fPng_ptr, fInfo_ptr, PNG_INFO_tRNS));
-
-                fSrcConfig = SkSwizzler::kGrayAlpha;
-            } else {
-                if (this->getInfo().alphaType() == kOpaque_SkAlphaType) {
-                    fSrcConfig = SkSwizzler::kRGB;
-                } else {
-                    fSrcConfig = SkSwizzler::kRGBA;
-                }
-            }
-            break;
+    if (SkEncodedInfo::kPalette_Color == this->getEncodedInfo().color()) {
+        if (!this->decodePalette(kPremul_SkAlphaType == requestedInfo.alphaType(),
+                requestedInfo.colorType(), ctableCount)) {
+            return kInvalidInput;
         }
-        default:
-            // We will always recommend one of the above colorTypes.
-            SkASSERT(false);
     }
 
     // Copy the color table to the client if they request kIndex8 mode
@@ -506,7 +464,8 @@ SkCodec::Result SkPngCodec::initializeSwizzler(const SkImageInfo& requestedInfo,
 
     // Create the swizzler.  SkPngCodec retains ownership of the color table.
     const SkPMColor* colors = get_color_ptr(fColorTable.get());
-    fSwizzler.reset(SkSwizzler::CreateSwizzler(fSrcConfig, colors, requestedInfo, options));
+    fSwizzler.reset(SkSwizzler::CreateSwizzler(this->getEncodedInfo(), colors, requestedInfo,
+            options));
     SkASSERT(fSwizzler);
 
     return kSuccess;
@@ -553,7 +512,7 @@ SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void*
 
     const int width = requestedInfo.width();
     const int height = requestedInfo.height();
-    const int bpp = SkSwizzler::BytesPerPixel(fSrcConfig);
+    const int bpp = this->getEncodedInfo().bytesPerPixel();
     const size_t srcRowBytes = width * bpp;
 
     // FIXME: Could we use the return value of setjmp to specify the type of
@@ -649,7 +608,7 @@ public:
             return result;
         }
 
-        fStorage.reset(this->getInfo().width() * SkSwizzler::BytesPerPixel(this->srcConfig()));
+        fStorage.reset(this->getInfo().width() * this->getEncodedInfo().bytesPerPixel());
         fSrcRow = fStorage.get();
 
         return kSuccess;
@@ -721,7 +680,7 @@ public:
 
         fHeight = dstInfo.height();
         // FIXME: This need not be called on a second call to onStartScanlineDecode.
-        fSrcRowBytes = this->getInfo().width() * SkSwizzler::BytesPerPixel(this->srcConfig());
+        fSrcRowBytes = this->getInfo().width() * this->getEncodedInfo().bytesPerPixel();
         fGarbageRow.reset(fSrcRowBytes);
         fGarbageRowPtr = static_cast<uint8_t*>(fGarbageRow.get());
         fCanSkipRewind = true;