Add SkEncodedInfo to report properties of encoded image data

src/codec/SkWebpCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodecPriv.h"
 #include "SkWebpCodec.h"
 #include "SkTemplates.h"
@@ skipping 13 matching lines @@
     // WEBP starts with the following:
     // RIFFXXXXWEBPVP
     // Where XXXX is unspecified.
     const char* bytes = static_cast<const char*>(buf);
     return bytesRead >= 14 && !memcmp(bytes, "RIFF", 4) && !memcmp(&bytes[8], "WEBPVP", 6);
 }
 
 // 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());
 
     const size_t bytesPeeked = stream->peek(buffer, WEBP_VP8_HEADER_SIZE);
     if (bytesPeeked != WEBP_VP8_HEADER_SIZE) {
         // Use read + rewind as a backup
         if (stream->read(buffer, WEBP_VP8_HEADER_SIZE) != WEBP_VP8_HEADER_SIZE
             || !stream->rewind())
         return false;
     }
@@ skipping 10 matching lines @@
         if (!sk_64_isS32(size)) {
             return false;
         }
         // now check that if we are 4-bytes per pixel, we also don't overflow
         if (sk_64_asS32(size) > (0x7FFFFFFF >> 2)) {
             return false;
         }
     }
 
     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());
     }
     return nullptr;
 }
 
 // This version is slightly different from SkCodecPriv's version of conversion_possible. It
 // supports both byte orders for 8888.
 static bool webp_conversion_possible(const SkImageInfo& dst, const SkImageInfo& src) {
     if (dst.profileType() != src.profileType()) {
@@ skipping 155 matching lines @@
                 return kSuccess;
             case VP8_STATUS_SUSPENDED:
                 // Break out of the switch statement. Continue the loop.
                 break;
             default:
                 return kInvalidInput;
         }
     }
 }
 
-SkWebpCodec::SkWebpCodec(const SkImageInfo& info, SkStream* stream)
+SkWebpCodec::SkWebpCodec(const SkEncodedInfo& info, SkStream* stream)
     : INHERITED(info, stream) {}