GIMP wrote bmp files in RGBX format. Huh.

include/SDL_pixels.h

@@ -212,9 +212,15 @@ enum
     SDL_PIXELFORMAT_RGB888 =
         SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_PACKED32, SDL_PACKEDORDER_XRGB,
                                SDL_PACKEDLAYOUT_8888, 24, 4),
+    SDL_PIXELFORMAT_RGBX8888 =
+        SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_PACKED32, SDL_PACKEDORDER_RGBX,
+                               SDL_PACKEDLAYOUT_8888, 24, 4),
     SDL_PIXELFORMAT_BGR888 =
         SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_PACKED32, SDL_PACKEDORDER_XBGR,
                                SDL_PACKEDLAYOUT_8888, 24, 4),
+    SDL_PIXELFORMAT_BGRX8888 =
+        SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_PACKED32, SDL_PACKEDORDER_BGRX,
+                               SDL_PACKEDLAYOUT_8888, 24, 4),
     SDL_PIXELFORMAT_ARGB8888 =
         SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_PACKED32, SDL_PACKEDORDER_ARGB,
                                SDL_PACKEDLAYOUT_8888, 32, 4),

src/video/SDL_pixels.c

@@ -109,7 +109,9 @@ SDL_GetPixelFormatName(Uint32 format)
     CASE(SDL_PIXELFORMAT_RGB24)
     CASE(SDL_PIXELFORMAT_BGR24)
     CASE(SDL_PIXELFORMAT_RGB888)
+    CASE(SDL_PIXELFORMAT_RGBX8888)
     CASE(SDL_PIXELFORMAT_BGR888)
+    CASE(SDL_PIXELFORMAT_BGRX8888)
     CASE(SDL_PIXELFORMAT_ARGB8888)
     CASE(SDL_PIXELFORMAT_RGBA8888)
     CASE(SDL_PIXELFORMAT_ABGR8888)
@@ -426,12 +428,24 @@ SDL_MasksToPixelFormatEnum(int bpp, Uint32 Rmask, Uint32 Gmask, Uint32 Bmask,
             Amask == 0x00000000) {
             return SDL_PIXELFORMAT_RGB888;
         }
+        if (Rmask == 0xFF000000 &&
+            Gmask == 0x00FF0000 &&
+            Bmask == 0x0000FF00 &&
+            Amask == 0x00000000) {
+            return SDL_PIXELFORMAT_RGBX8888;
+        }
         if (Rmask == 0x000000FF &&
             Gmask == 0x0000FF00 &&
             Bmask == 0x00FF0000 &&
             Amask == 0x00000000) {
             return SDL_PIXELFORMAT_BGR888;
         }
+        if (Rmask == 0x0000FF00 &&
+            Gmask == 0x00FF0000 &&
+            Bmask == 0xFF000000 &&
+            Amask == 0x00000000) {
+            return SDL_PIXELFORMAT_BGRX8888;
+        }
         if (Rmask == 0x00FF0000 &&
             Gmask == 0x0000FF00 &&
             Bmask == 0x000000FF &&