[PATCH v4 0/2] MR8988: win32u: change the stretch mode of dst hdc from BlackOnWhite to ColorOnColor...

[Kun Yang (＠yangkun)]

win32u: change the stretch mode of dst hdc from BlackOnWhite to ColorOnColor when using StretchBlt in TransparentBlt.

In NtGdiTransparentBlt function, the StretchBlt mode of dst hdc is not set. The Default StretchBlt Mode in wine is BlackOnWhite. It is not correct to use this StretchBltMode in TransparentBlt dealing with color bitmap. According to MSDN, it should be converted to ColorOnColor.
My test code shows that, the image converted by wine generates a lot of chromatic noise.

[test_blt.c](/uploads/26101bc7bdb27400d02c8ff5bf741864/test_blt.c)

[test_blt.exe](/uploads/98ee3ab7ce0d590e1511bd8a5fb5a1bb/test_blt.exe)

![source](/uploads/0c56c5e6d1280040ba08cd3dee7acd95/source.bmp)

![result_wrong](/uploads/2076396e069f852914313a8fb86dd5e2/result_wrong.bmp)

![result](/uploads/cf3ec00bf0f0e7f3ea7fe1e2085385d6/result.bmp)

--
  v4: Apply 1 suggestion(s) to 1 file(s)

https://gitlab.winehq.org/wine/wine/-/merge_requests/8988

[PATCH v4 1/2] win32u: change the stretch mode of dst hdc from BlackOnWhite to ColorOnColor when using StretchBlt in TransparentBlt.

[yangkun]

From: yangkun

Signed-off-by: yangkun 
Change-Id: Ic3c64a5d2ffef7d890f461b089223fbd7a972ffd
---
 dlls/win32u/bitblt.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/dlls/win32u/bitblt.c b/dlls/win32u/bitblt.c
index a9f6f70daf6..d8c8aace7f0 100644
--- a/dlls/win32u/bitblt.c
+++ b/dlls/win32u/bitblt.c
@@ -857,6 +857,7 @@ BOOL WINAPI NtGdiTransparentBlt( HDC hdcDest, int xDest, int yDest, int widthDes
     int oldStretchMode;
     DIBSECTION dib;
     DC *dc_src;
+    DC *dc_work;

if(widthDest < 0 || heightDest < 0 || widthSrc < 0 || heightSrc < 0) {
         TRACE("Cannot mirror\n");
@@ -890,6 +891,11 @@ BOOL WINAPI NtGdiTransparentBlt( HDC hdcDest, int xDest, int yDest, int widthDes
     }
     else bmpWork = NtGdiCreateCompatibleBitmap( hdcDest, widthDest, heightDest );
     oldWork = NtGdiSelectBitmap(hdcWork, bmpWork);
+
+    if (!(dc_work = get_dc_ptr(hdcWork))) goto error;
+    dc_work->attr->stretch_blt_mode = COLORONCOLOR;
+    release_dc_ptr( dc_work );
+
     if (!NtGdiStretchBlt( hdcWork, 0, 0, widthDest, heightDest, hdcSrc, xSrc, ySrc,
                           widthSrc, heightSrc, SRCCOPY, 0 ))
     {
@@ -937,6 +943,7 @@ error:
     release_dc_ptr( dc_src );
     NtGdiGetAndSetDCDword( hdcDest, NtGdiSetBkColor, oldBackground, NULL );
     NtGdiGetAndSetDCDword( hdcDest, NtGdiSetTextColor, oldForeground, NULL );
+
     if(hdcWork) {
         NtGdiSelectBitmap(hdcWork, oldWork);
         NtGdiDeleteObjectApp( hdcWork );

[PATCH v4 2/2] Apply 1 suggestion(s) to 1 file(s)

[Kun Yang]

From: Kun Yang

Co-authored-by: Jinoh Kang 
---
 dlls/win32u/bitblt.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/dlls/win32u/bitblt.c b/dlls/win32u/bitblt.c
index d8c8aace7f0..7721d3b4b73 100644
--- a/dlls/win32u/bitblt.c
+++ b/dlls/win32u/bitblt.c
@@ -943,7 +943,6 @@ error:
     release_dc_ptr( dc_src );
     NtGdiGetAndSetDCDword( hdcDest, NtGdiSetBkColor, oldBackground, NULL );
     NtGdiGetAndSetDCDword( hdcDest, NtGdiSetTextColor, oldForeground, NULL );
-
     if(hdcWork) {
         NtGdiSelectBitmap(hdcWork, oldWork);
         NtGdiDeleteObjectApp( hdcWork );

[Kun Yang (＠yangkun)]

On Tue Oct 14 11:34:18 2025 +0000, Kun Yang wrote:
> changed this line in [version 4 of the diff](/wine/wine/-/merge_requests/8988/diffs?diff_id=216296&start_sha=9f893d8b4f1200eb6ed91d42ddb272a5108fbc1d#f3d97f0145ff57de291f14eb7521d8afbbb7f7ac_946_946)

@iamahuman I have addressed the suggestion.

[Jinoh Kang (＠iamahuman)]

Please squash your fix commit into the original commit.