chrome/browser/ui/libgtk2ui/skia_utils_gtk2.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
   6
   7 #include <gdk/gdk.h>
   8
   9 #include "base/basictypes.h"
  10 #include "base/logging.h"
  11 #include "third_party/skia/include/core/SkBitmap.h"
  12 #include "third_party/skia/include/core/SkUnPreMultiply.h"
  13
  14 namespace libgtk2ui {
  15
  16 const int kSkiaToGDKMultiplier = 257;
  17
  18 // GDK_COLOR_RGB multiplies by 257 (= 0x10001) to distribute the bits evenly
  19 // See: http://www.mindcontrol.org/~hplus/graphics/expand-bits.html
  20 // To get back, we can just right shift by eight
  21 // (or, formulated differently, i == (i*257)/256 for all i < 256).
  22
  23 SkColor GdkColorToSkColor(GdkColor color) {
  24   return SkColorSetRGB(color.red >> 8, color.green >> 8, color.blue >> 8);
  25 }
  26
  27 GdkColor SkColorToGdkColor(SkColor color) {
  28   GdkColor gdk_color = {
  29       0,
  30       static_cast<guint16>(SkColorGetR(color) * kSkiaToGDKMultiplier),
  31       static_cast<guint16>(SkColorGetG(color) * kSkiaToGDKMultiplier),
  32       static_cast<guint16>(SkColorGetB(color) * kSkiaToGDKMultiplier)
  33   };
  34   return gdk_color;
  35 }
  36
  37 const SkBitmap GdkPixbufToImageSkia(GdkPixbuf* pixbuf) {
  38   // TODO(erg): What do we do in the case where the pixbuf fails these dchecks?
  39   // I would prefer to use our gtk based canvas, but that would require
  40   // recompiling half of our skia extensions with gtk support, which we can't
  41   // do in this build.
  42   DCHECK_EQ(GDK_COLORSPACE_RGB, gdk_pixbuf_get_colorspace(pixbuf));
  43
  44   int n_channels = gdk_pixbuf_get_n_channels(pixbuf);
  45   int w = gdk_pixbuf_get_width(pixbuf);
  46   int h = gdk_pixbuf_get_height(pixbuf);
  47
  48   SkBitmap ret;
  49   ret.setConfig(SkBitmap::kARGB_8888_Config, w, h);
  50   ret.allocPixels();
  51   ret.eraseColor(0);
  52
  53   uint32_t* skia_data = static_cast<uint32_t*>(ret.getAddr(0, 0));
  54
  55   if (n_channels == 4) {
  56     int total_length = w * h;
  57     guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
  58
  59     // Now here's the trick: we need to convert the gdk data (which is RGBA and
  60     // isn't premultiplied) to skia (which can be anything and premultiplied).
  61     for (int i = 0; i < total_length; ++i, gdk_pixels += 4) {
  62       const unsigned char& red = gdk_pixels[0];
  63       const unsigned char& green = gdk_pixels[1];
  64       const unsigned char& blue = gdk_pixels[2];
  65       const unsigned char& alpha = gdk_pixels[3];
  66
  67       skia_data[i] = SkPreMultiplyARGB(alpha, red, green, blue);
  68     }
  69   } else if (n_channels == 3) {
  70     // Because GDK makes rowstrides word aligned, we need to do something a bit
  71     // more complex when a pixel isn't perfectly a word of memory.
  72     int rowstride = gdk_pixbuf_get_rowstride(pixbuf);
  73     guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
  74     for (int y = 0; y < h; ++y) {
  75       int row = y * rowstride;
  76
  77       for (int x = 0; x < w; ++x) {
  78         guchar* pixel = gdk_pixels + row + (x * 3);
  79         const unsigned char& red = pixel[0];
  80         const unsigned char& green = pixel[1];
  81         const unsigned char& blue = pixel[2];
  82
  83         skia_data[y * w + x] = SkPreMultiplyARGB(255, red, green, blue);
  84       }
  85     }
  86   } else {
  87     NOTREACHED();
  88   }
  89
  90   return ret;
  91 }
  92
  93 GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap& bitmap) {
  94   if (bitmap.isNull())
  95     return NULL;
  96
  97   SkAutoLockPixels lock_pixels(bitmap);
  98
  99   int width = bitmap.width();
 100   int height = bitmap.height();
 101
 102   GdkPixbuf* pixbuf =
 103       gdk_pixbuf_new(GDK_COLORSPACE_RGB,  // The only colorspace gtk supports.
 104                      TRUE,                // There is an alpha channel.
 105                      8,
 106                      width,
 107                      height);
 108
 109   // SkBitmaps are premultiplied, we need to unpremultiply them.
 110   const int kBytesPerPixel = 4;
 111   uint8* divided = gdk_pixbuf_get_pixels(pixbuf);
 112
 113   for (int y = 0, i = 0; y < height; y++) {
 114     for (int x = 0; x < width; x++) {
 115       uint32 pixel = bitmap.getAddr32(0, y)[x];
 116
 117       int alpha = SkColorGetA(pixel);
 118       if (alpha != 0 && alpha != 255) {
 119         SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(pixel);
 120         divided[i + 0] = SkColorGetR(unmultiplied);
 121         divided[i + 1] = SkColorGetG(unmultiplied);
 122         divided[i + 2] = SkColorGetB(unmultiplied);
 123         divided[i + 3] = alpha;
 124       } else {
 125         divided[i + 0] = SkColorGetR(pixel);
 126         divided[i + 1] = SkColorGetG(pixel);
 127         divided[i + 2] = SkColorGetB(pixel);
 128         divided[i + 3] = alpha;
 129       }
 130       i += kBytesPerPixel;
 131     }
 132   }
 133
 134   return pixbuf;
 135 }
 136
 137 }  // namespace libgtk2ui