[PATCH 1/4] comctl32/imagelist: Pre-multiply rgb by the alpha channel in add_dib_bits for v6.

[Ziqing Hui]

From: Ziqing Hui

We used to do this when drawing the image. But our tests show that for v6,
the image bitmaps have been alpha pre-multiplied before drawing.
So we should do this when adding images.
---
 dlls/comctl32/imagelist.c       | 32 +++++++++++++++++++++++---------
 dlls/comctl32/tests/imagelist.c |  3 +--
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/dlls/comctl32/imagelist.c b/dlls/comctl32/imagelist.c
index 493aebd0b45..ea9b69e1291 100644
--- a/dlls/comctl32/imagelist.c
+++ b/dlls/comctl32/imagelist.c
@@ -200,6 +200,21 @@ static inline void imagelist_copy_images( HIMAGELIST himl, HDC hdcSrc, HDC hdcDe
     }
 }

+static void premultiply_alpha_channel(DWORD *bits, int pixel_count)
+{
+    DWORD *ptr = bits;
+    unsigned int i;
+
+    for (i = 0; i < pixel_count; i++, ptr++)
+    {
+        DWORD alpha = *ptr >> 24;
+        *ptr = ((*ptr & 0xff000000)
+                | (((*ptr & 0x00ff0000) * alpha / 255) & 0x00ff0000)
+                | (((*ptr & 0x0000ff00) * alpha / 255) & 0x0000ff00)
+                | (((*ptr & 0x000000ff) * alpha / 255)));
+    }
+}
+
 static void add_dib_bits( HIMAGELIST himl, int pos, int count, int width, int height,
                           BITMAPINFO *info, BITMAPINFO *mask_info, DWORD *bits, BYTE *mask_bits )
 {
@@ -223,6 +238,11 @@ static void add_dib_bits( HIMAGELIST himl, int pos, int count, int width, int he
         {
             himl->item_flags[pos + n] = ILIF_ALPHA;

+#if __WINE_COMCTL32_VERSION == 6
+            for (i = 0; i < height; i++)
+                premultiply_alpha_channel(&bits[i * stride + n * width], width);
+#endif /* __WINE_COMCTL32_VERSION == 6 */
+
             if (mask_info && himl->hbmMask)  /* generate the mask from the alpha channel */
             {
                 for (i = 0; i < height; i++)
@@ -1236,15 +1256,9 @@ static BOOL alpha_blend_image( HIMAGELIST himl, HDC dest_dc, int dest_x, int des

if (has_alpha)  /* we already have an alpha channel in this case */
     {
-        /* pre-multiply by the alpha channel */
-        for (i = 0, ptr = bits; i < cx * cy; i++, ptr++)
-        {
-            DWORD alpha = *ptr >> 24;
-            *ptr = ((*ptr & 0xff000000) |
-                    (((*ptr & 0x00ff0000) * alpha / 255) & 0x00ff0000) |
-                    (((*ptr & 0x0000ff00) * alpha / 255) & 0x0000ff00) |
-                    (((*ptr & 0x000000ff) * alpha / 255)));
-        }
+#if __WINE_COMCTL32_VERSION == 5
+        premultiply_alpha_channel(bits, cx * cy);
+#endif /* __WINE_COMCTL32_VERSION == 5 */
     }
     else if (himl->hbmMask)
     {
diff --git a/dlls/comctl32/tests/imagelist.c b/dlls/comctl32/tests/imagelist.c
index 3b547732fd5..7cd23a9da2f 100644
--- a/dlls/comctl32/tests/imagelist.c
+++ b/dlls/comctl32/tests/imagelist.c
@@ -2580,7 +2580,6 @@ static void test_alpha(BOOL v6)
         }

image_list_get_image_bits_by_bitmap(himl, i / 2, bits);
-        todo_wine_if(v6 && i != 0 && i != 2 && i != 4 && i != 6 && i != 12 && i != 18)
         ok(colour_match(bits[0], expected[0]) && colour_match(bits[1], expected[1]),
                 "Got bits [%08X, %08X], expected [%08X, %08X].\n",
                 bits[0], bits[1], expected[0], expected[1]);
@@ -2639,7 +2638,7 @@ static void test_alpha(BOOL v6)
         }

image_list_get_image_bits_by_bitmap(himl, i / 2, bits);
-        todo_wine_if(i != 0 && i != 2 && i != 4 && i != 6 && (!v6 || i != 18))
+        todo_wine_if(i != 0 && i != 2 && i != 4 && i != 6 && !v6)
         ok(colour_match(bits[0], expected[0]) && colour_match(bits[1], expected[1]),
                 "Got bits [%08X, %08X], expected [%08X, %08X].\n",
                 bits[0], bits[1], expected[0], expected[1]);