store SkAlphaType inside SkBitmap, on road to support unpremul

src/images/SkImageDecoder_libpng.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkImageDecoder.h"
@@ skipping 419 matching lines @@
     if (0 != theTranspColor) {
         reallyHasAlpha |= substituteTranspColor(decodedBitmap, theTranspColor);
     }
     if (reallyHasAlpha && this->getRequireUnpremultipliedColors() &&
         SkBitmap::kARGB_8888_Config != decodedBitmap->config()) {
         // If the caller wants an unpremultiplied bitmap, and we let them get
         // away with a config other than 8888, and it has alpha after all,
         // return false, since the result will have premultiplied colors.
         return false;
     }
-    decodedBitmap->setIsOpaque(!reallyHasAlpha);
+    decodedBitmap->setAlphaType(reallyHasAlpha ? kPremul_SkAlphaType : kOpaque_SkAlphaType);

[scroggo, 2013/10/02 18:49:58]

In addition to checking for unpremultiply, this needs to check the config for
A8, as in https://codereview.chromium.org/25726004/

[reed1, 2013/10/03 08:22:54]

Not sure what the change to the code should be. If the png is A8, I presume
reallyHasAlpha will be true, in which case I'll store kPremul. Is that not
correct?

[scroggo, 2013/10/03 14:05:19]

It doesn't currently change reallyHasAlpha, but it could. My latest patch
changes reallyHasAlpha.

This code still needs to check this->getRequireUnpremultipliedColors(). If true,
the alpha type should be kUnpremul.

[reed1, 2013/10/18 15:27:06]

Done.

     return true;
 }
 
 
 
 bool SkPNGImageDecoder::getBitmapConfig(png_structp png_ptr, png_infop info_ptr,
                                         SkBitmap::Config* SK_RESTRICT configp,
                                         bool* SK_RESTRICT hasAlphap,
                                         bool* SK_RESTRICT doDitherp,
                                         SkPMColor* SK_RESTRICT theTranspColorp) {
@@ skipping 431 matching lines @@
                 if (y < height - 1) {
                     skip_src_rows(png_ptr, srcRow, sampler.srcDY() - 1);
                 }
             }
         }
     }
 
     if (0 != theTranspColor) {
         reallyHasAlpha |= substituteTranspColor(&decodedBitmap, theTranspColor);
     }
-    decodedBitmap.setIsOpaque(!reallyHasAlpha);
+    decodedBitmap.setAlphaType(reallyHasAlpha ? kPremul_SkAlphaType : kOpaque_SkAlphaType);
 
     if (swapOnly) {
         bm->swap(decodedBitmap);
         return true;
     }
     return this->cropBitmap(bm, &decodedBitmap, sampleSize, region.x(), region.y(),
                             region.width(), region.height(), 0, rect.y());
 }
 #endif
 
@@ skipping 294 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? SkNEW(SkPNGImageEncoder) : NULL;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libpng_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_png);
 static SkImageEncoder_EncodeReg gEReg(sk_libpng_efactory);