Fixes for unpremul decode.

src/ports/SkImageDecoder_CG.cpp

-
 /*
  * Copyright 2008 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 "SkCGUtils.h"
 #include "SkColorPriv.h"
-
 #include "SkImageDecoder.h"
 #include "SkImageEncoder.h"
 #include "SkMovie.h"
 #include "SkStream.h"
 #include "SkTemplates.h"
-#include "SkCGUtils.h"
+#include "SkUnPreMultiply.h"
 
 #ifdef SK_BUILD_FOR_MAC
 #include <ApplicationServices/ApplicationServices.h>
 #endif
 
 #ifdef SK_BUILD_FOR_IOS
 #include <CoreGraphics/CoreGraphics.h>
 #include <ImageIO/ImageIO.h>
 #include <MobileCoreServices/MobileCoreServices.h>
 #endif
@@ skipping 16 matching lines @@
     CGImageSourceRef imageSrc = CGImageSourceCreateWithDataProvider(data, 0);
     CGDataProviderRelease(data);
     return imageSrc;
 }
 
 class SkImageDecoder_CG : public SkImageDecoder {
 protected:
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode);
 };
 
+// Returns an unpremultiplied version of color. It will have the same ordering and size as an
+// SkPMColor, but the alpha will not be premultiplied.
+static SkPMColor unpremultiply_pmcolor(SkPMColor color) {
+    U8CPU a = SkGetPackedA32(color);

[reed1, 2013/06/14 19:38:20]

possibly only do this if a is != 0xFF and a != 0 ?

+    const SkUnPreMultiply::Scale scale = SkUnPreMultiply::GetScale(a);
+    return SkPackARGB32NoCheck(a,
+                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedR32(color)),
+                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedG32(color)),
+                               SkUnPreMultiply::ApplyScale(scale, SkGetPackedB32(color)));
+}
+
 #define BITMAP_INFO (kCGBitmapByteOrder32Big | kCGImageAlphaPremultipliedLast)
 
 bool SkImageDecoder_CG::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
     CGImageSourceRef imageSrc = SkStreamToCGImageSource(stream);
 
     if (NULL == imageSrc) {
         return false;
     }
     SkAutoTCallVProc<const void, CFRelease> arsrc(imageSrc);
 
@@ skipping 10 matching lines @@
         return true;
     }
 
     if (!this->allocPixelRef(bm, NULL)) {
         return false;
     }
 
     bm->lockPixels();
     bm->eraseColor(SK_ColorTRANSPARENT);
 
-    // use the same colorspace, so we don't change the pixels at all
-    CGColorSpaceRef cs = CGImageGetColorSpace(image);
+    CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
     CGContextRef cg = CGBitmapContextCreate(bm->getPixels(), width, height, 8, bm->rowBytes(), cs, BITMAP_INFO);
-    if (NULL == cg) {
-        // perhaps the image's colorspace does not work for a context, so try just rgb
-        cs = CGColorSpaceCreateDeviceRGB();
-        cg = CGBitmapContextCreate(bm->getPixels(), width, height, 8, bm->rowBytes(), cs, BITMAP_INFO);
-        CFRelease(cs);
-    }
+    CFRelease(cs);
+
     CGContextDrawImage(cg, CGRectMake(0, 0, width, height), image);
     CGContextRelease(cg);
 
     CGImageAlphaInfo info = CGImageGetAlphaInfo(image);
     switch (info) {
         case kCGImageAlphaNone:
         case kCGImageAlphaNoneSkipLast:
         case kCGImageAlphaNoneSkipFirst:
             SkASSERT(SkBitmap::ComputeIsOpaque(*bm));
             bm->setIsOpaque(true);
             break;
         default:
             // we don't know if we're opaque or not, so compute it.
             bm->computeAndSetOpaquePredicate();
     }
+    if (!bm->isOpaque() && this->getRequireUnpremultipliedColors()) {
+        // CGBitmapContext does not support unpremultiplied, so the image has been premultiplied.
+        // Convert to unpremultiplied.
+        for (int i = 0; i < width; ++i) {
+            for (int j = 0; j < height; ++j) {
+                uint32_t* addr = bm->getAddr32(i, j);
+                *addr = unpremultiply_pmcolor(*addr);
+            }
+        }
+    }
     bm->unlockPixels();
     return true;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 extern SkImageDecoder* image_decoder_from_stream(SkStream*);
 
 SkImageDecoder* SkImageDecoder::Factory(SkStream* stream) {
     SkImageDecoder* decoder = image_decoder_from_stream(stream);
@@ skipping 163 matching lines @@
 
     SkAutoTCallVProc<const void, CFRelease> arsrc(imageSrc);
     const CFStringRef name = CGImageSourceGetType(imageSrc);
     if (NULL == name) {
         return SkImageDecoder::kUnknown_Format;
     }
     return UTType_to_Format(name);
 }
 
 static SkTRegistry<SkImageDecoder::Format, SkStream*> gFormatReg(get_format_cg);