Support more color types for ICOs

src/codec/SkBmpCodec.cpp

Index: src/codec/SkBmpCodec.cpp
diff --git a/src/codec/SkBmpCodec.cpp b/src/codec/SkBmpCodec.cpp
index 3302e4f752eb74826b6142d1d3e04535e393f816..f5a87709f779b25d4f4bba4abd160af46e62fe3f 100644
--- a/src/codec/SkBmpCodec.cpp
+++ b/src/codec/SkBmpCodec.cpp
@@ -472,6 +472,14 @@ bool SkBmpCodec::ReadHeader(SkStream* stream, bool inIco, SkCodec** codecOut) {
     }
 
     if (codecOut) {
+        // BMPs-in-ICOs contain an alpha mask after the image which means we
+        // cannot guarantee that an image is opaque, even if the bmp thinks
+        // it is.
+        bool isOpaque = kOpaque_SkAlphaType == alphaType;

[msarett, 2016/02/11 16:50:15]

Here we need to remember if the embedded BMP is actually opaque.  Since we will
always suggest kUnpremul for BMP-in-ICOs.

Another approach would be handle this in SkIcoCodec similar to how we did
before:

if (embeddedCodec is a bmp) {
    recommendedInfo = recommendedInfo.makeAlphaType(kUnpremul);
}

This would be simpler than the current code (no modifications to SkBmpCodec).

The drawback would be that we would print warnings on Ico decodes.
Ex: "BMP said it was opaque but is being decoded as if it is kUnpremul/Premul"

[scroggo, 2016/02/11 18:05:13]

This seems simple enough to me.

[msarett, 2016/02/11 18:15:47]

Acknowledged.

+        if (inIco) {
+            alphaType = kUnpremul_SkAlphaType;
+        }
+
         // Set the image info
         const SkImageInfo& imageInfo = SkImageInfo::Make(width, height,
                 colorType, alphaType);
@@ -482,7 +490,7 @@ bool SkBmpCodec::ReadHeader(SkStream* stream, bool inIco, SkCodec** codecOut) {
                 // We require streams to have a memory base for Bmp-in-Ico decodes.
                 SkASSERT(!inIco || nullptr != stream->getMemoryBase());
                 *codecOut = new SkBmpStandardCodec(imageInfo, stream, bitsPerPixel, numColors,
-                        bytesPerColor, offset - bytesRead, rowOrder, inIco);
+                        bytesPerColor, offset - bytesRead, rowOrder, isOpaque, inIco);
                 return true;
             case kBitMask_BmpInputFormat:
                 // Bmp-in-Ico must be standard mode