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 // GDK_COLOR_RGB multiplies by 257 (= 0x10001) to distribute the bits evenly
  17 // See: http://www.mindcontrol.org/~hplus/graphics/expand-bits.html
  18 // To get back, we can just right shift by eight
  19 // (or, formulated differently, i == (i*257)/256 for all i < 256).
  20
  21 SkColor GdkColorToSkColor(GdkColor color) {
  22   return SkColorSetRGB(color.red >> 8, color.green >> 8, color.blue >> 8);
  23 }
  24
  25 GdkColor SkColorToGdkColor(SkColor color) {
  26   GdkColor gdk_color = {
  27       0,
  28       static_cast<guint16>(SkColorGetR(color) * kSkiaToGDKMultiplier),
  29       static_cast<guint16>(SkColorGetG(color) * kSkiaToGDKMultiplier),
  30       static_cast<guint16>(SkColorGetB(color) * kSkiaToGDKMultiplier)
  31   };
  32   return gdk_color;
  33 }
  34
  35 const SkBitmap GdkPixbufToImageSkia(GdkPixbuf* pixbuf) {
  36   // TODO(erg): What do we do in the case where the pixbuf fails these dchecks?
  37   // I would prefer to use our gtk based canvas, but that would require
  38   // recompiling half of our skia extensions with gtk support, which we can't
  39   // do in this build.
  40   DCHECK_EQ(GDK_COLORSPACE_RGB, gdk_pixbuf_get_colorspace(pixbuf));
  41
  42   int n_channels = gdk_pixbuf_get_n_channels(pixbuf);
  43   int w = gdk_pixbuf_get_width(pixbuf);
  44   int h = gdk_pixbuf_get_height(pixbuf);
  45
  46   SkBitmap ret;
  47   ret.allocN32Pixels(w, h);
  48   ret.eraseColor(0);
  49
  50   uint32_t* skia_data = static_cast<uint32_t*>(ret.getAddr(0, 0));
  51
  52   if (n_channels == 4) {
  53     int total_length = w * h;
  54     guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
  55
  56     // Now here's the trick: we need to convert the gdk data (which is RGBA and
  57     // isn't premultiplied) to skia (which can be anything and premultiplied).
  58     for (int i = 0; i < total_length; ++i, gdk_pixels += 4) {
  59       const unsigned char& red = gdk_pixels[0];
  60       const unsigned char& green = gdk_pixels[1];
  61       const unsigned char& blue = gdk_pixels[2];
  62       const unsigned char& alpha = gdk_pixels[3];
  63
  64       skia_data[i] = SkPreMultiplyARGB(alpha, red, green, blue);
  65     }
  66   } else if (n_channels == 3) {
  67     // Because GDK makes rowstrides word aligned, we need to do something a bit
  68     // more complex when a pixel isn't perfectly a word of memory.
  69     int rowstride = gdk_pixbuf_get_rowstride(pixbuf);
  70     guchar* gdk_pixels = gdk_pixbuf_get_pixels(pixbuf);
  71     for (int y = 0; y < h; ++y) {
  72       int row = y * rowstride;
  73
  74       for (int x = 0; x < w; ++x) {
  75         guchar* pixel = gdk_pixels + row + (x * 3);
  76         const unsigned char& red = pixel[0];
  77         const unsigned char& green = pixel[1];
  78         const unsigned char& blue = pixel[2];
  79
  80         skia_data[y * w + x] = SkPreMultiplyARGB(255, red, green, blue);
  81       }
  82     }
  83   } else {
  84     NOTREACHED();
  85   }
  86
  87   return ret;
  88 }
  89
  90 GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap& bitmap) {
  91   if (bitmap.isNull())
  92     return NULL;
  93
  94   SkAutoLockPixels lock_pixels(bitmap);
  95
  96   int width = bitmap.width();
  97   int height = bitmap.height();
  98
  99   GdkPixbuf* pixbuf =
 100       gdk_pixbuf_new(GDK_COLORSPACE_RGB,  // The only colorspace gtk supports.
 101                      TRUE,                // There is an alpha channel.
 102                      8,
 103                      width,
 104                      height);
 105
 106   // SkBitmaps are premultiplied, we need to unpremultiply them.
 107   const int kBytesPerPixel = 4;
 108   uint8* divided = gdk_pixbuf_get_pixels(pixbuf);
 109
 110   for (int y = 0, i = 0; y < height; y++) {
 111     for (int x = 0; x < width; x++) {
 112       uint32 pixel = bitmap.getAddr32(0, y)[x];
 113
 114       int alpha = SkColorGetA(pixel);
 115       if (alpha != 0 && alpha != 255) {
 116         SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(pixel);
 117         divided[i + 0] = SkColorGetR(unmultiplied);
 118         divided[i + 1] = SkColorGetG(unmultiplied);
 119         divided[i + 2] = SkColorGetB(unmultiplied);
 120         divided[i + 3] = alpha;
 121       } else {
 122         divided[i + 0] = SkColorGetR(pixel);
 123         divided[i + 1] = SkColorGetG(pixel);
 124         divided[i + 2] = SkColorGetB(pixel);
 125         divided[i + 3] = alpha;
 126       }
 127       i += kBytesPerPixel;
 128     }
 129   }
 130
 131   return pixbuf;
 132 }
 133
 134 }  // namespace libgtk2ui