Piotr Caban : gdiplus: Use transparency instead of background color if transparent color flag is set in GIF GCE.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 333a63c456fec24f249a7096b1d858252c9a6bf4
URL:    https://gitlab.winehq.org/wine/wine/-/commit/333a63c456fec24f249a7096b1d8582...

Author: Piotr Caban <piotr(a)codeweavers.com>
Date:   Fri Mar  3 15:56:29 2023 +0100

gdiplus: Use transparency instead of background color if transparent color flag is set in GIF GCE.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=54563

---

 dlls/gdiplus/image.c       | 16 +++---------
 dlls/gdiplus/tests/image.c | 65 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 67 insertions(+), 14 deletions(-)

diff --git a/dlls/gdiplus/image.c b/dlls/gdiplus/image.c
index 101e7ae1c93..3b9ce3c14f1 100644
--- a/dlls/gdiplus/image.c
+++ b/dlls/gdiplus/image.c
@@ -3881,20 +3881,10 @@ static DWORD get_gif_background_color(GpBitmap *bitmap)
     UINT i;
 
     for(i=0; i<bitmap->prop_count; i++) {
-        if(bitmap->prop_item[i].id == PropertyTagIndexBackground) {
+        if(bitmap->prop_item[i].id == PropertyTagIndexBackground)
             bgcolor_idx = *(BYTE*)bitmap->prop_item[i].value;
-            break;
-        }
-    }
-
-    for(i=0; i<bitmap->prop_count; i++) {
-        if(bitmap->prop_item[i].id == PropertyTagIndexTransparent) {
-            BYTE transparent_idx;
-            transparent_idx = *(BYTE*)bitmap->prop_item[i].value;
-
-            if(transparent_idx == bgcolor_idx)
-                return 0;
-        }
+        else if(bitmap->prop_item[i].id == PropertyTagIndexTransparent)
+            return 0;
     }
 
     for(i=0; i<bitmap->prop_count; i++) {
diff --git a/dlls/gdiplus/tests/image.c b/dlls/gdiplus/tests/image.c
index 9e35cf33eb4..e32b4c81240 100644
--- a/dlls/gdiplus/tests/image.c
+++ b/dlls/gdiplus/tests/image.c
@@ -2899,10 +2899,11 @@ static const unsigned char gifanimation[72] = {
  *     -dispose previous -page +4+0 -size 2x2 xc:green \
  *     -dispose undefined -page +6+0 -size 2x2 xc:gray \
  *     test.gif
+ * Background color index changed to 1.
  */
 static const unsigned char gifanimation2[] = {
     0x47, 0x49, 0x46, 0x38, 0x39, 0x61, 0x08, 0x00,
-    0x02, 0x00, 0xf0, 0x00, 0x00, 0x00, 0x00, 0x00,
+    0x02, 0x00, 0xf0, 0x01, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x21, 0xf9, 0x04, 0x01, 0x64,
     0x00, 0x00, 0x00, 0x21, 0xff, 0x0b, 0x4e, 0x45,
     0x54, 0x53, 0x43, 0x41, 0x50, 0x45, 0x32, 0x2e,
@@ -2937,6 +2938,43 @@ static ARGB gifanimation2_pixels[5][4] = {
     {0xffff0000, 0, 0, 0xff7e7e7e}
 };
 
+static const unsigned char gifanimation3[] = {
+    0x47, 0x49, 0x46, 0x38, 0x39, 0x61, 0x08, 0x00,
+    0x02, 0x00, 0xf0, 0x01, 0x00, 0x00, 0x00, 0x00,
+    0x00, 0x00, 0x00, 0x21, 0xf9, 0x04, 0x00, 0x64,
+    0x00, 0x00, 0x00, 0x21, 0xff, 0x0b, 0x4e, 0x45,
+    0x54, 0x53, 0x43, 0x41, 0x50, 0x45, 0x32, 0x2e,
+    0x30, 0x03, 0x01, 0x00, 0x00, 0x00, 0x2c, 0x00,
+    0x00, 0x00, 0x00, 0x08, 0x00, 0x02, 0x00, 0x00,
+    0x02, 0x04, 0x84, 0x8f, 0x09, 0x05, 0x00, 0x21,
+    0xf9, 0x04, 0x05, 0x64, 0x00, 0x10, 0x00, 0x2c,
+    0x00, 0x00, 0x00, 0x00, 0x02, 0x00, 0x02, 0x00,
+    0x81, 0xff, 0x00, 0x00, 0xff, 0x00, 0x00, 0xff,
+    0x00, 0x00, 0xff, 0x00, 0x00, 0x02, 0x03, 0x44,
+    0x34, 0x05, 0x00, 0x21, 0xf9, 0x04, 0x09, 0x64,
+    0x00, 0x10, 0x00, 0x2c, 0x02, 0x00, 0x00, 0x00,
+    0x02, 0x00, 0x02, 0x00, 0x81, 0x00, 0x00, 0xff,
+    0x00, 0x00, 0xff, 0x00, 0x00, 0xff, 0x00, 0x00,
+    0xff, 0x02, 0x03, 0x44, 0x34, 0x05, 0x00, 0x21,
+    0xf9, 0x04, 0x0d, 0x64, 0x00, 0x10, 0x00, 0x2c,
+    0x04, 0x00, 0x00, 0x00, 0x02, 0x00, 0x02, 0x00,
+    0x81, 0x00, 0x80, 0x00, 0x00, 0x80, 0x00, 0x00,
+    0x80, 0x00, 0x00, 0x80, 0x00, 0x02, 0x03, 0x44,
+    0x34, 0x05, 0x00, 0x21, 0xf9, 0x04, 0x01, 0x64,
+    0x00, 0x10, 0x00, 0x2c, 0x06, 0x00, 0x00, 0x00,
+    0x02, 0x00, 0x02, 0x00, 0x80, 0x7e, 0x7e, 0x7e,
+    0x00, 0x00, 0x00, 0x02, 0x02, 0x84, 0x51, 0x00,
+    0x3b
+};
+
+static ARGB gifanimation3_pixels[5][4] = {
+    {0xff000000, 0xff000000, 0xff000000, 0xff000000},
+    {0xffff0000, 0xff000000, 0xff000000, 0xff000000},
+    {0xffff0000, 0xff0000ff, 0xff000000, 0xff000000},
+    {0xffff0000, 0xff000000, 0xff008000, 0xff000000},
+    {0xffff0000, 0xff000000, 0xff000000, 0xff7e7e7e}
+};
+
 static void test_multiframegif(void)
 {
     LPSTREAM stream;
@@ -3185,6 +3223,31 @@ static void test_multiframegif(void)
     }
 
     GdipDisposeImage((GpImage*)bmp);
+
+    hglob = GlobalAlloc (0, sizeof(gifanimation3));
+    data = GlobalLock (hglob);
+    memcpy(data, gifanimation3, sizeof(gifanimation3));
+    GlobalUnlock(hglob);
+
+    hres = CreateStreamOnHGlobal(hglob, TRUE, &stream);
+    ok(hres == S_OK, "Failed to create a stream\n");
+
+    stat = GdipCreateBitmapFromStream(stream, &bmp);
+    ok(stat == Ok, "Failed to create a Bitmap\n");
+    IStream_Release(stream);
+
+    for(i=0; i<6; i++) {
+        stat = GdipImageSelectActiveFrame((GpImage*)bmp, &dimension, i%5);
+        expect(Ok, stat);
+
+        for(j=0; j<4; j++) {
+            stat = GdipBitmapGetPixel(bmp, j*2, 0, &color);
+            expect(Ok, stat);
+            ok(gifanimation3_pixels[i%5][j] == color, "at %d,%d got %lx, expected %lx\n", i, j, color, gifanimation3_pixels[i%5][j]);
+        }
+    }
+
+    GdipDisposeImage((GpImage*)bmp);
 }
 
 static void test_rotateflip(void)