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chrome/browser/ui/libgtk2ui/skia_utils_gtk2.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
 
 #include <gdk/gdk.h>
 
+#include "base/basictypes.h"
+#include "base/logging.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "third_party/skia/include/core/SkUnPreMultiply.h"
+
 namespace libgtk2ui {
 
 const int kSkiaToGDKMultiplier = 257;
 
 // GDK_COLOR_RGB multiplies by 257 (= 0x10001) to distribute the bits evenly
 // See: http://www.mindcontrol.org/~hplus/graphics/expand-bits.html
 // To get back, we can just right shift by eight
 // (or, formulated differently, i == (i*257)/256 for all i < 256).
 
 SkColor GdkColorToSkColor(GdkColor color) {
   return SkColorSetRGB(color.red >> 8, color.green >> 8, color.blue >> 8);
 }
 
 GdkColor SkColorToGdkColor(SkColor color) {
   GdkColor gdk_color = {
       0,
       static_cast<guint16>(SkColorGetR(color) * kSkiaToGDKMultiplier),
       static_cast<guint16>(SkColorGetG(color) * kSkiaToGDKMultiplier),
       static_cast<guint16>(SkColorGetB(color) * kSkiaToGDKMultiplier)
   };
   return gdk_color;
 }
 
+const SkBitmap GdkPixbufToImageSkia(GdkPixbuf* pixbuf) {
+  // TODO(erg): What do we do in the case where the pixbuf fails these dchecks?
+  // I would prefer to use our gtk based canvas, but that would require
+  // recompiling half of our skia extensions with gtk support, which we can't
+  // do in this build.
+  DCHECK_EQ(GDK_COLORSPACE_RGB, gdk_pixbuf_get_colorspace(pixbuf));
+
+  int n_channels = gdk_pixbuf_get_n_channels(pixbuf);
+  int w = gdk_pixbuf_get_width(pixbuf);
+  int h = gdk_pixbuf_get_height(pixbuf);
+
+  SkBitmap ret;
+  ret.setConfig(SkBitmap::kARGB_8888_Config, w, h);
+  ret.allocPixels();
+  ret.eraseColor(0);
+
+  uint32_t* skia_data = static_cast<uint32_t*>(ret.getAddr(0, 0));
+
+  if (n_channels == 4) {
+    int total_length = w * h;
+    guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
+
+    // Now here's the trick: we need to convert the gdk data (which is RGBA and
+    // isn't premultiplied) to skia (which can be anything and premultiplied).
+    for (int i = 0; i < total_length; ++i, gdk_pixels += 4) {
+      const unsigned char& red = gdk_pixels[0];
+      const unsigned char& green = gdk_pixels[1];
+      const unsigned char& blue = gdk_pixels[2];
+      const unsigned char& alpha = gdk_pixels[3];
+
+      skia_data[i] = SkPreMultiplyARGB(alpha, red, green, blue);
+    }
+  } else if (n_channels == 3) {
+    // Because GDK makes rowstrides word aligned, we need to do something a bit
+    // more complex when a pixel isn't perfectly a word of memory.
+    int rowstride = gdk_pixbuf_get_rowstride(pixbuf);
+    guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
+    for (int y = 0; y < h; ++y) {
+      int row = y * rowstride;
+
+      for (int x = 0; x < w; ++x) {
+        guchar* pixel = gdk_pixels + row + (x * 3);
+        const unsigned char& red = pixel[0];
+        const unsigned char& green = pixel[1];
+        const unsigned char& blue = pixel[2];
+
+        skia_data[y * w + x] = SkPreMultiplyARGB(255, red, green, blue);
+      }
+    }
+  } else {
+    NOTREACHED();
+  }
+
+  return ret;
+}
+
+GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap& bitmap) {
+  if (bitmap.isNull())
+    return NULL;
+
+  SkAutoLockPixels lock_pixels(bitmap);
+
+  int width = bitmap.width();
+  int height = bitmap.height();
+
+  GdkPixbuf* pixbuf =
+      gdk_pixbuf_new(GDK_COLORSPACE_RGB,  // The only colorspace gtk supports.
+                     TRUE,                // There is an alpha channel.
+                     8,
+                     width,
+                     height);
+
+  // SkBitmaps are premultiplied, we need to unpremultiply them.
+  const int kBytesPerPixel = 4;
+  uint8* divided = gdk_pixbuf_get_pixels(pixbuf);
+
+  for (int y = 0, i = 0; y < height; y++) {
+    for (int x = 0; x < width; x++) {
+      uint32 pixel = bitmap.getAddr32(0, y)[x];
+
+      int alpha = SkColorGetA(pixel);
+      if (alpha != 0 && alpha != 255) {
+        SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(pixel);
+        divided[i + 0] = SkColorGetR(unmultiplied);
+        divided[i + 1] = SkColorGetG(unmultiplied);
+        divided[i + 2] = SkColorGetB(unmultiplied);
+        divided[i + 3] = alpha;
+      } else {
+        divided[i + 0] = SkColorGetR(pixel);
+        divided[i + 1] = SkColorGetG(pixel);
+        divided[i + 2] = SkColorGetB(pixel);
+        divided[i + 3] = alpha;
+      }
+      i += kBytesPerPixel;
+    }
+  }
+
+  return pixbuf;
+}
+
 }  // namespace libgtk2ui