Add SkEncodedInfo to report properties of encoded image data

src/codec/SkWebpCodec.cpp

Index: src/codec/SkWebpCodec.cpp
diff --git a/src/codec/SkWebpCodec.cpp b/src/codec/SkWebpCodec.cpp
index a795fdd6d551637467cdf95fae5b4cffb07691d8..a60b3ab8a83451afbe52b01514f695ef910c7ff4 100644
--- a/src/codec/SkWebpCodec.cpp
+++ b/src/codec/SkWebpCodec.cpp
@@ -31,7 +31,7 @@ bool SkWebpCodec::IsWebp(const void* buf, size_t bytesRead) {
 // Parse headers of RIFF container, and check for valid Webp (VP8) content.
 // NOTE: This calls peek instead of read, since onGetPixels will need these
 // bytes again.
-static bool webp_parse_header(SkStream* stream, SkImageInfo* info) {
+static bool webp_parse_header(SkStream* stream, SkEncodedInfo* info) {
     unsigned char buffer[WEBP_VP8_HEADER_SIZE];
     SkASSERT(WEBP_VP8_HEADER_SIZE <= SkCodec::MinBufferedBytesNeeded());
 
@@ -62,20 +62,18 @@ static bool webp_parse_header(SkStream* stream, SkImageInfo* info) {
     }
 
     if (info) {
-        // FIXME: Is N32 the right type?
-        // Is unpremul the right type? Clients of SkCodec may assume it's the
-        // best type, when Skia currently cannot draw unpremul (and raster is faster
-        // with premul).
-        *info = SkImageInfo::Make(features.width, features.height, kN32_SkColorType,
-                                  SkToBool(features.has_alpha) ? kUnpremul_SkAlphaType
-                                                              : kOpaque_SkAlphaType);
+        SkEncodedInfo::Color color = SkToBool(features.has_alpha) ? SkEncodedInfo::kYUVA_Color :
+                SkEncodedInfo::kYUV_Color;
+        SkEncodedInfo::Alpha alpha = SkToBool(features.has_alpha) ? SkEncodedInfo::kUnpremul_Alpha :

[scroggo, 2016/03/23 14:48:50]

How does alpha work for a YUV image? Is "unpremul" descriptive here? Or should
it have a separate value?

[msarett, 2016/03/24 16:20:44]

Thanks for questioning this.  I dug a little deeper into the webp format.  Turns
out kUnpremul and 8 bits per component are correct, but I've gotten some other
stuff wrong...

+                SkEncodedInfo::kOpaque_Alpha;
+        *info = SkEncodedInfo::Make(features.width, features.height, color, alpha, 8);

[scroggo, 2016/03/23 14:48:50]

Similarly, is 8 bits per component meaningful here?

[msarett, 2016/03/24 16:20:44]

Acknowledged.

     }
     return true;
 }
 
 SkCodec* SkWebpCodec::NewFromStream(SkStream* stream) {
     SkAutoTDelete<SkStream> streamDeleter(stream);
-    SkImageInfo info;
+    SkEncodedInfo info;
     if (webp_parse_header(stream, &info)) {
         return new SkWebpCodec(info, streamDeleter.release());
     }
@@ -251,5 +249,5 @@ SkCodec::Result SkWebpCodec::onGetPixels(const SkImageInfo& dstInfo, void* dst,
     }
 }
 
-SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream)
+SkWebpCodec::SkWebpCodec(const SkEncodedInfo& info, SkStream* stream)
     : INHERITED(info, stream) {}