Windows: Fix opacity of drag images.

BUG=XXX
TEST=Go to google.com, drag logo around. Preview image should now look nice.

Review URL: http://codereview.chromium.org/2963009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@52484 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 27 insertions, 0 deletions

diff --git a/gfx/skbitmap_operations.cc b/gfx/skbitmap_operations.cc
index 27508ba..b8cec11 100644
--- a/gfx/skbitmap_operations.cc
+++ b/gfx/skbitmap_operations.cc
@@ -668,3 +668,30 @@ SkBitmap SkBitmapOperations::DownsampleByTwo(const SkBitmap& bitmap) {
   return result;
 }
 
+// static
+SkBitmap SkBitmapOperations::UnPreMultiply(const SkBitmap& bitmap) {
+  if (bitmap.isNull())
+    return bitmap;
+  if (bitmap.isOpaque())
+    return bitmap;
+
+  SkBitmap opaque_bitmap;
+  opaque_bitmap.setConfig(bitmap.config(), bitmap.width(), bitmap.height());
+  opaque_bitmap.allocPixels();
+
+  {
+    SkAutoLockPixels bitmap_lock(bitmap);
+    SkAutoLockPixels opaque_bitmap_lock(opaque_bitmap);
+    for (int y = 0; y < opaque_bitmap.height(); y++) {
+      for (int x = 0; x < opaque_bitmap.width(); x++) {
+        uint32 src_pixel = *bitmap.getAddr32(x, y);
+        uint32* dst_pixel = opaque_bitmap.getAddr32(x, y);
+        SkColor unmultiplied = SkUnPreMultiply::PMColorToColor(src_pixel);
+        *dst_pixel = unmultiplied;
+      }
+    }
+  }
+
+  opaque_bitmap.setIsOpaque(true);
+  return opaque_bitmap;
+}