Add an option to create unpremultiplied bitmaps.

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 62 matching lines @@
 #ifdef SK_BUILD_FOR_ANDROID
     virtual bool onBuildTileIndex(SkStream *stream, int *width, int *height) SK_OVERRIDE;
     virtual bool onDecodeSubset(SkBitmap* bitmap, const SkIRect& region) SK_OVERRIDE;
 #endif
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode) SK_OVERRIDE;
 
 private:
     SkPNGImageIndex* fImageIndex;
 
     bool onDecodeInit(SkStream* stream, png_structp *png_ptrp, png_infop *info_ptrp);
-    bool decodePalette(png_structp png_ptr, png_infop info_ptr, bool *hasAlphap,
-                       bool *reallyHasAlphap, SkColorTable **colorTablep);
+    bool decodePalette(png_structp png_ptr, png_infop info_ptr,
+                       bool * SK_RESTRICT hasAlphap, bool *reallyHasAlphap,
+                       SkColorTable **colorTablep);
     bool getBitmapConfig(png_structp png_ptr, png_infop info_ptr,
                          SkBitmap::Config *config, bool *hasAlpha,
                          bool *doDither, SkPMColor *theTranspColor);
 
     typedef SkImageDecoder INHERITED;
 };
 
 #ifndef png_jmpbuf
 #  define png_jmpbuf(png_ptr) ((png_ptr)->jmpbuf)
 #endif
@@ skipping 209 matching lines @@
     bool reuseBitmap = (rowptr != NULL);
     decodedBitmap->unlockPixels();
     if (reuseBitmap && (sampler.scaledWidth() != decodedBitmap->width() ||
                         sampler.scaledHeight() != decodedBitmap->height())) {
         // Dimensions must match
         return false;
     }
 
     if (!reuseBitmap) {
         decodedBitmap->setConfig(config, sampler.scaledWidth(),
-                                 sampler.scaledHeight(), 0);
+                                 sampler.scaledHeight());
     }
     if (SkImageDecoder::kDecodeBounds_Mode == mode) {
         return true;
     }
 
     // from here down we are concerned with colortables and pixels
 
     // we track if we actually see a non-opaque pixels, since sometimes a PNG sets its colortype
     // to |= PNG_COLOR_MASK_ALPHA, but all of its pixels are in fact opaque. We care, since we
     // draw lots faster if we can flag the bitmap has being opaque
@@ skipping 103 matching lines @@
             skip_src_rows(png_ptr, srcRow, origHeight - read);
         }
     }
 
     /* read rest of file, and get additional chunks in info_ptr - REQUIRED */
     png_read_end(png_ptr, info_ptr);
 
     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);
     if (reuseBitmap) {
         decodedBitmap->notifyPixelsChanged();
     }
     return true;
 }
 
 
 
 bool SkPNGImageDecoder::getBitmapConfig(png_structp png_ptr, png_infop info_ptr,
-                                        SkBitmap::Config *configp, bool *hasAlphap,
+                                        SkBitmap::Config *configp, bool * SK_RESTRICT hasAlphap,
                                         bool *doDitherp, SkPMColor *theTranspColorp) {
     png_uint_32 origWidth, origHeight;
     int bitDepth, colorType;
     png_get_IHDR(png_ptr, info_ptr, &origWidth, &origHeight, &bitDepth,
                  &colorType, int_p_NULL, int_p_NULL, int_p_NULL);
 
     // check for sBIT chunk data, in case we should disable dithering because
     // our data is not truely 8bits per component
     png_color_8p sig_bit;
     if (*doDitherp && png_get_sBIT(png_ptr, info_ptr, &sig_bit)) {
@@ skipping 80 matching lines @@
         size.setMul(origWidth, origHeight);
         if (size.isNeg() || !size.is32()) {
             return false;
         }
         // now check that if we are 4-bytes per pixel, we also don't overflow
         if (size.get32() > (0x7FFFFFFF >> 2)) {
             return false;
         }
     }
 
-    return this->chooseFromOneChoice(*configp, origWidth, origHeight);
+    if (!this->chooseFromOneChoice(*configp, origWidth, origHeight)) {
+        return false;
+    }
+
+    // If the image has alpha and the decoder wants unpremultiplied
+    // colors, the only supported config is 8888.
+    if (this->getRequireUnpremultipliedColors() && *hasAlphap) {
+        *configp = SkBitmap::kARGB_8888_Config;
+    }
+    return true;
 }
 
+typedef uint32_t (*PackColorProc)(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
+
 bool SkPNGImageDecoder::decodePalette(png_structp png_ptr, png_infop info_ptr,
                                       bool *hasAlphap, bool *reallyHasAlphap,
                                       SkColorTable **colorTablep) {
     int numPalette;
     png_colorp palette;
     png_bytep trans;
     int numTrans;
     bool reallyHasAlpha = false;
     SkColorTable* colorTable = NULL;
 
@@ skipping 18 matching lines @@
         colorTable->setFlags(colorTable->getFlags() | SkColorTable::kColorsAreOpaque_Flag);
     }
     // check for bad images that might make us crash
     if (numTrans > numPalette) {
         numTrans = numPalette;
     }
 
     int index = 0;
     int transLessThanFF = 0;
 
+    // Choose which function to use to create the color table. If the final destination's
+    // config is unpremultiplied, the color table will store unpremultiplied colors.
+    PackColorProc proc;
+    if (this->getRequireUnpremultipliedColors()) {
+        proc = &SkPackARGB32NoCheck;
+    } else {
+        proc = &SkPreMultiplyARGB;
+    }
     for (; index < numTrans; index++) {
         transLessThanFF |= (int)*trans - 0xFF;
-        *colorPtr++ = SkPreMultiplyARGB(*trans++, palette->red, palette->green, palette->blue);
+        *colorPtr++ = proc(*trans++, palette->red, palette->green, palette->blue);
         palette++;
     }
     reallyHasAlpha |= (transLessThanFF < 0);
 
     for (; index < numPalette; index++) {
         *colorPtr++ = SkPackARGB32(0xFF, palette->red, palette->green, palette->blue);
         palette++;
     }
 
     // see BUGGY IMAGE WORKAROUND comment above
@@ skipping 69 matching lines @@
     SkPMColor           theTranspColor = 0; // 0 tells us not to try to match
 
     if (!getBitmapConfig(png_ptr, info_ptr, &config, &hasAlpha, &doDither, &theTranspColor)) {
         return false;
     }
 
     const int sampleSize = this->getSampleSize();
     SkScaledBitmapSampler sampler(origWidth, rect.height(), sampleSize);
 
     SkBitmap decodedBitmap;
-    decodedBitmap.setConfig(config, sampler.scaledWidth(), sampler.scaledHeight(), 0);
+    decodedBitmap.setConfig(config, sampler.scaledWidth(), sampler.scaledHeight());
 
     // from here down we are concerned with colortables and pixels
 
     // we track if we actually see a non-opaque pixels, since sometimes a PNG sets its colortype
     // to |= PNG_COLOR_MASK_ALPHA, but all of its pixels are in fact opaque. We care, since we
     // draw lots faster if we can flag the bitmap has being opaque
     bool reallyHasAlpha = false;
     SkColorTable* colorTable = NULL;
 
     if (colorType == PNG_COLOR_TYPE_PALETTE) {
-        decodePalette(png_ptr, info_ptr, &hasAlpha, &reallyHasAlpha, &colorTable);
+        decodePalette(png_ptr, info_ptr, config, &hasAlpha, &reallyHasAlpha, &colorTable);
     }
 
     SkAutoUnref aur(colorTable);
 
     // Check ahead of time if the swap(dest, src) is possible.
     // 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() / sampleSize;
     int h = rect.height() / sampleSize;
     const bool swapOnly = (rect == region) && (w == decodedBitmap.width()) &&
@@ skipping 433 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 SkImageEncoder* sk_libpng_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kPNG_Type == t) ? SkNEW(SkPNGImageEncoder) : NULL;
 }
 
 static SkTRegistry<SkImageEncoder*, SkImageEncoder::Type> gEReg(sk_libpng_efactory);
 static SkTRegistry<SkImageDecoder::Format, SkStream*> gFormatReg(get_format_png);
 static SkTRegistry<SkImageDecoder*, SkStream*> gDReg(sk_libpng_dfactory);