b=359002, single pixel background image is incorrect color (third line of acid2), r=stuart

gfx/src/thebes/nsThebesImage.cpp

@@ -216,16 +216,13 @@ nsThebesImage::Optimize(nsIDeviceContext* aContext)
         if (mFormat == gfxImageSurface::ImageFormatARGB32 ||
             mFormat == gfxImageSurface::ImageFormatRGB24)
         {
-            PRUint32 *pxl = (PRUint32 *) mImageSurface->Data();
-            mSinglePixelColor = gfxRGBA(*pxl);
-            if (mFormat == gfxImageSurface::ImageFormatRGB24)
-                mSinglePixelColor.a = 1.0;
-            else if (mSinglePixelColor.a != 0.0) {
-                // unpremultiply alpha
-                mSinglePixelColor.r = mSinglePixelColor.r / mSinglePixelColor.a;
-                mSinglePixelColor.g = mSinglePixelColor.g / mSinglePixelColor.a;
-                mSinglePixelColor.b = mSinglePixelColor.b / mSinglePixelColor.a;
-            }
+            PRUint32 pixel = *((PRUint32 *) mImageSurface->Data());
+
+            mSinglePixelColor = gfxRGBA
+                (pixel,
+                 (mFormat == gfxImageSurface::ImageFormatRGB24 ?
+                  gfxRGBA::PACKED_XRGB :
+                  gfxRGBA::PACKED_ARGB_PREMULTIPLIED));
 
             mSinglePixel = PR_TRUE;
 

gfx/thebes/public/gfxColor.h

@@ -52,6 +52,17 @@
 struct THEBES_API gfxRGBA {
     gfxFloat r, g, b, a;
 
+    enum PackedColorType {
+        PACKED_ABGR,
+        PACKED_ABGR_PREMULTIPLIED,
+
+        PACKED_ARGB,
+        PACKED_ARGB_PREMULTIPLIED,
+
+        PACKED_XBGR,
+        PACKED_XRGB
+    };
+
     gfxRGBA() { }
     gfxRGBA(const gfxRGBA& c) : r(c.r), g(c.g), b(c.b), a(c.a) {}
     /**
@@ -59,39 +70,87 @@ struct THEBES_API gfxRGBA {
      * values.
      */
     gfxRGBA(gfxFloat _r, gfxFloat _g, gfxFloat _b, gfxFloat _a=1.0) : r(_r), g(_g), b(_b), a(_a) {}
+
     /**
      * Initialize this color from a packed 32-bit color.
-     * Premultiplied alpha isn't used.
-     * This uses ABGR byte order in the native endianness.
+     * The color value is interpreted based on colorType;
+     * all values use the native platform endianness.
      *
      * @see gfxRGBA::Packed
      */
-    gfxRGBA(PRUint32 c) {
-        r = ((c >> 0) & 0xff) / 255.0;
-        g = ((c >> 8) & 0xff) / 255.0;
-        b = ((c >> 16) & 0xff) / 255.0;
-        a = ((c >> 24) & 0xff) / 255.0;
+    gfxRGBA(PRUint32 c, PackedColorType colorType = PACKED_ABGR) {
+        if (colorType == PACKED_ABGR ||
+            colorType == PACKED_XBGR)
+        {
+            r = ((c >> 0) & 0xff) / 255.0;
+            g = ((c >> 8) & 0xff) / 255.0;
+            b = ((c >> 16) & 0xff) / 255.0;
+            a = ((c >> 24) & 0xff) / 255.0;
+        } else if (colorType == PACKED_ARGB ||
+                   colorType == PACKED_XRGB)
+        {
+            b = ((c >> 0) & 0xff) / 255.0;
+            g = ((c >> 8) & 0xff) / 255.0;
+            r = ((c >> 16) & 0xff) / 255.0;
+            a = ((c >> 24) & 0xff) / 255.0;
+        }
+
+        if (colorType == PACKED_ABGR_PREMULTIPLIED ||
+            colorType == PACKED_ARGB_PREMULTIPLIED)
+        {
+            if (a > 0.0) {
+                r /= a;
+                g /= a;
+                b /= a;
+            }
+        } else if (colorType == PACKED_XBGR ||
+                   colorType == PACKED_XRGB)
+        {
+            a = 1.0;
+        }
     }
+
     /**
      * Initialize this color by parsing the given string.
+     * XXX implement me!
      */
+#if 0
     gfxRGBA(const char* str) {
         a = 1.0;
         // if aString[0] is a #, parse it as hex
         // if aString[0] is a letter, parse it as a color name
         // if aString[0] is a number, parse it loosely as hex
     }
+#endif
 
     /**
-     * Returns this color value as a packed 32-bit integer. This uses ABGR
-     * byte order in the native endianness, as accepted by the corresponding
-     * constructor of this class.
+     * Returns this color value as a packed 32-bit integer. This reconstructs
+     * the int32 based on the given colorType, always in the native byte order.
      */
-    PRUint32 Packed() const {
-        return (((PRUint8)(a * 255.0) << 24) |
-                ((PRUint8)(b * 255.0) << 16) |
-                ((PRUint8)(g * 255.0) << 8) |
-                ((PRUint8)(r * 255.0)));
+    PRUint32 Packed(PackedColorType colorType = PACKED_ABGR) const {
+        if (colorType == PACKED_ABGR || colorType == PACKED_XBGR) {
+            return (((PRUint8)(a * 255.0) << 24) |
+                    ((PRUint8)(b * 255.0) << 16) |
+                    ((PRUint8)(g * 255.0) << 8) |
+                    ((PRUint8)(r * 255.0)));
+        } else if (colorType == PACKED_ARGB || colorType == PACKED_XRGB) {
+            return (((PRUint8)(a * 255.0) << 24) |
+                    ((PRUint8)(r * 255.0) << 16) |
+                    ((PRUint8)(g * 255.0) << 8) |
+                    ((PRUint8)(b * 255.0)));
+        } else if (colorType == PACKED_ABGR_PREMULTIPLIED) {
+            return (((PRUint8)(a * 255.0) << 24) |
+                    ((PRUint8)((b*a) * 255.0) << 16) |
+                    ((PRUint8)((g*a) * 255.0) << 8) |
+                    ((PRUint8)((r*a) * 255.0)));
+        } else if (colorType == PACKED_ARGB_PREMULTIPLIED) {
+            return (((PRUint8)(a * 255.0) << 24) |
+                    ((PRUint8)((r*a) * 255.0) << 16) |
+                    ((PRUint8)((g*a) * 255.0) << 8) |
+                    ((PRUint8)((b*a) * 255.0)));
+        } else {
+            return 0;
+        }
     }
 
     /**