iamahuman · March 13, 2022 23:09 · Mar 13, 2022
diff --git a/gdi_argb8888_to_pargb8888.c b/gdi_argb8888_to_pargb8888.c
@@ -0,0 +1,50 @@
+#define WIN32_LEAN_AND_MEAN
+#define WINVER 0x0601
+#define _WIN32_WINNT 0x0601
+#include <windows.h>
+
+HBITMAP argb8888_to_pargb8888(HBITMAP hbm, HDC hdc)
+{
+    const BLENDFUNCTION blendfn = { AC_SRC_OVER, 0, 0xff, AC_SRC_ALPHA };
+    HDC hdcSrc, hdcTmp1, hdcTmp2;
+    HBITMAP hbmRes = NULL, hbmTmp1, hbmTmp2;
+    HBRUSH hbrwhite;
+    BITMAP bitmap;
+    INT width, height;
+
+    if (GetObjectType(hbm) != OBJ_BITMAP) goto done;
+    if (!GetObject(hbm, sizeof(BITMAP), &bitmap)) goto done;
+    width = bitmap.bmWidth;
+    height = bitmap.bmHeight;
+
+    if (!(hbrwhite = GetStockObject(WHITE_BRUSH))) goto done;
+    if (!(hdcSrc = CreateCompatibleDC(hdc))) goto done;
+    if (!SelectObject(hdcSrc, hbm)) goto free_hdcSrc;
+    if (!(hbmTmp1 = CreateCompatibleBitmap(hdcSrc, width, height))) goto free_hdcSrc;
+    if (!(hbmTmp2 = CreateCompatibleBitmap(hdcSrc, width, height))) goto free_hbmTmp1;
+    if (!(hdcTmp1 = CreateCompatibleDC(hdcSrc))) goto free_hbmTmp2;
+    if (!SelectObject(hdcTmp1, hbmTmp1)) goto free_hdcTmp1;
+    if (!SelectObject(hdcTmp1, hbrwhite)) goto free_hdcTmp1;
+    if (!(hdcTmp2 = CreateCompatibleDC(hdcSrc))) goto free_hdcTmp1;
+    if (!SelectObject(hdcTmp2, hbmTmp2)) goto free_hdcTmp2;
+    if (!SelectObject(hdcTmp2, hbrwhite)) goto free_hdcTmp2;
+    if (!BitBlt(hdcTmp1, 0, 0, width, height, hdcSrc, 0, 0, MERGECOPY /* PSa */)) goto free_hdcTmp2;
+    if (!BitBlt(hdcTmp2, 0, 0, width, height, hdcSrc, 0, 0, 0x000300AA /* PSon */)) goto free_hdcTmp2;
+    if (!GdiAlphaBlend(hdcTmp1, 0, 0, width, height, hdcTmp2, 0, 0, width, height, blendfn)) goto free_hdcTmp2;
+    if (!PatBlt(hdcTmp1, 0, 0, width, height, 0x00A50065 /* PDxn */)) goto free_hdcTmp2;
+
+    hbmRes = hbmTmp1; hbmTmp1 = NULL;
+
+free_hdcTmp2:
+    DeleteDC(hdcTmp2);
+free_hdcTmp1:
+    DeleteDC(hdcTmp1);
+free_hbmTmp2:
+    if (hbmTmp2) DeleteObject(hbmTmp2);
+free_hbmTmp1:
+    if (hbmTmp1) DeleteObject(hbmTmp1);
+free_hdcSrc:
+    DeleteDC(hdcSrc);
+done:
+    return hbmRes;
+}