Set the alpha channel for less than 32-bit ICO/CUR images

slouken · slouken · commit f1e4fff0c920 · 2025-03-03T13:24:22.000-08:00
Fixes #532 (cherry picked from commit d415332)
diff --git a/CHANGES.txt b/CHANGES.txt
@@ -1,3 +1,6 @@
+2.8.8:
+ * Fixed alpha in less than 32-bit ICO and CUR images
+
 2.8.6:
  * Fixed partial alpha in ICO and CUR images
 
diff --git a/src/IMG_bmp.c b/src/IMG_bmp.c
@@ -307,6 +307,11 @@ LoadICOCUR_RW(SDL_RWops * src, int type, int freesrc)
         }
         for (i = 0; i < (int) biClrUsed; ++i) {
             SDL_RWread(src, &palette[i], 4, 1);
+
+            /* Since biSize == 40, we know alpha is reserved and should be zero, meaning opaque */
+            if ((palette[i] & 0xFF000000) == 0) {
+                palette[i] |= 0xFF000000;
+            }
         }
     }
 
@@ -361,7 +366,7 @@ LoadICOCUR_RW(SDL_RWops * src, int type, int freesrc)
                 Uint32 pixel;
                 Uint8 channel;
                 for (i = 0; i < surface->w; ++i) {
-                    pixel = 0;
+                    pixel = 0xFF000000;
                     for (j = 0; j < 3; ++j) {
                         /* Load each color channel into pixel */
                         if (!SDL_RWread(src, &channel, 1, 1)) {

Original file line number	Diff line number	Diff line change
`@@ -307,6 +307,11 @@ LoadICOCUR_RW(SDL_RWops * src, int type, int freesrc)`
`307`	`307`	`}`
`308`	`308`	`for (i = 0; i < (int) biClrUsed; ++i) {`
`309`	`309`	`SDL_RWread(src, &palette[i], 4, 1);`
	`310`	`+`
	`311`	`+ /* Since biSize == 40, we know alpha is reserved and should be zero, meaning opaque */`
	`312`	`+ if ((palette[i] & 0xFF000000) == 0) {`
	`313`	`+ palette[i] \|= 0xFF000000;`
	`314`	`+ }`
`310`	`315`	`}`
`311`	`316`	`}`
`312`	`317`
`@@ -361,7 +366,7 @@ LoadICOCUR_RW(SDL_RWops * src, int type, int freesrc)`
`361`	`366`	`Uint32 pixel;`
`362`	`367`	`Uint8 channel;`
`363`	`368`	`for (i = 0; i < surface->w; ++i) {`
`364`		`- pixel = 0;`
	`369`	`+ pixel = 0xFF000000;`
`365`	`370`	`for (j = 0; j < 3; ++j) {`
`366`	`371`	`/* Load each color channel into pixel */`
`367`	`372`	`if (!SDL_RWread(src, &channel, 1, 1)) {`