store SkAlphaType inside SkBitmap, on road to support unpremul

src/images/SkImageDecoder_libjpeg.cpp

 /*
  * Copyright 2007 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"
 #include "SkImageEncoder.h"
@@ skipping 525 matching lines @@
 
     turn_off_visual_optimizations(&cinfo);
 
     const SkBitmap::Config config = this->getBitmapConfig(&cinfo);
 
 #ifdef ANDROID_RGB
     adjust_out_color_space_and_dither(&cinfo, config, *this);
 #endif
 
     if (1 == sampleSize && SkImageDecoder::kDecodeBounds_Mode == mode) {
-        bm->setConfig(config, cinfo.image_width, cinfo.image_height);
-        bm->setIsOpaque(config != SkBitmap::kA8_Config);
-        return true;
+        return bm->setConfig(config, cinfo.image_width, cinfo.image_height, 0,
+                             SkBitmap::kA8_Config == config ?
+                                kPremul_SkAlphaType : kOpaque_SkAlphaType);
     }
 
     /*  image_width and image_height are the original dimensions, available
         after jpeg_read_header(). To see the scaled dimensions, we have to call
         jpeg_start_decompress(), and then read output_width and output_height.
     */
     if (!jpeg_start_decompress(&cinfo)) {
         /*  If we failed here, we may still have enough information to return
             to the caller if they just wanted (subsampled bounds). If sampleSize
             was 1, then we would have already returned. Thus we just check if
             we're in kDecodeBounds_Mode, and that we have valid output sizes.
 
             One reason to fail here is that we have insufficient stream data
             to complete the setup. However, output dimensions seem to get
             computed very early, which is why this special check can pay off.
          */
         if (SkImageDecoder::kDecodeBounds_Mode == mode && valid_output_dimensions(cinfo)) {
             SkScaledBitmapSampler smpl(cinfo.output_width, cinfo.output_height,
                                        recompute_sampleSize(sampleSize, cinfo));
-            bm->setConfig(config, smpl.scaledWidth(), smpl.scaledHeight());
-            bm->setIsOpaque(config != SkBitmap::kA8_Config);
-            return true;
+            return bm->setConfig(config, smpl.scaledWidth(), smpl.scaledHeight(),
+                                 0, SkBitmap::kA8_Config == config ?
+                                    kPremul_SkAlphaType : kOpaque_SkAlphaType);
         } else {
             return return_false(cinfo, *bm, "start_decompress");
         }
     }
     sampleSize = recompute_sampleSize(sampleSize, cinfo);
 
     // should we allow the Chooser (if present) to pick a config for us???
     if (!this->chooseFromOneChoice(config, cinfo.output_width, cinfo.output_height)) {
         return return_false(cinfo, *bm, "chooseFromOneChoice");
     }
 
     SkScaledBitmapSampler sampler(cinfo.output_width, cinfo.output_height, sampleSize);
-    bm->setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
-    bm->setIsOpaque(config != SkBitmap::kA8_Config);
+    bm->setConfig(config, sampler.scaledWidth(), sampler.scaledHeight(), 0,
+                  SkBitmap::kA8_Config != config ? kOpaque_SkAlphaType : kPremul_SkAlphaType);

[scroggo, 2013/10/18 19:32:40]

nit: It's a little confusing that this call to setConfig negates the equality
check.

     if (SkImageDecoder::kDecodeBounds_Mode == mode) {
         return true;
     }
     if (!this->allocPixelRef(bm, NULL)) {
         return return_false(cinfo, *bm, "allocPixelRef");
     }
 
     SkAutoLockPixels alp(*bm);
 
 #ifdef ANDROID_RGB
@@ skipping 199 matching lines @@
     int height = rect.height();
 
     jpeg_init_read_tile_scanline(cinfo, fImageIndex->huffmanIndex(),
                                  &startX, &startY, &width, &height);
     int skiaSampleSize = recompute_sampleSize(requestedSampleSize, *cinfo);
     int actualSampleSize = skiaSampleSize * (DCTSIZE / cinfo->min_DCT_scaled_size);
 
     SkScaledBitmapSampler sampler(width, height, skiaSampleSize);
 
     SkBitmap bitmap;
-    bitmap.setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
-    bitmap.setIsOpaque(true);
+    bitmap.setConfig(config, sampler.scaledWidth(), sampler.scaledHeight(), 0,
+                     kOpaque_SkAlphaType);
 
     // Check ahead of time if the swap(dest, src) is possible or not.
     // If yes, then we will stick to AllocPixelRef since it's cheaper with the
     // swap happening. If no, then we will use alloc to allocate pixels to
     // prevent garbage collection.
     int w = rect.width() / actualSampleSize;
     int h = rect.height() / actualSampleSize;
     bool swapOnly = (rect == region) && bm->isNull() &&
                     (w == bitmap.width()) && (h == bitmap.height()) &&
                     ((startX - rect.x()) / actualSampleSize == 0) &&
@@ skipping 399 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 static SkImageEncoder* sk_libjpeg_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kJPEG_Type == t) ? SkNEW(SkJPEGImageEncoder) : NULL;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libjpeg_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_jpeg);
 static SkImageEncoder_EncodeReg gEReg(sk_libjpeg_efactory);