diff options
| -rw-r--r-- | libnsgif.c | 12 |
1 files changed, 10 insertions, 2 deletions
@@ -91,6 +91,10 @@ */ #define GIF_MAX_LZW 12 +/* Transparent colour +*/ +#define GIF_TRANSPARENT_COLOUR 0x00 + /* GIF Flags */ #define GIF_FRAME_COMBINE 1 @@ -876,7 +880,10 @@ gif_result gif_decode_frame(gif_animation *gif, unsigned int frame) { * colour or this is the first frame, clear the frame data */ if ((frame == 0) || (gif->decoded_frame == GIF_INVALID_FRAME)) { - memset((char*)frame_data, colour_table[gif->background_index], gif->width * gif->height * sizeof(int)); + memset((char*)frame_data, GIF_TRANSPARENT_COLOUR, gif->width * gif->height * sizeof(int)); + /* The line below would fill the image with its background color, but because GIFs support + * transparency we likely wouldn't want to do that. */ + /* memset((char*)frame_data, colour_table[gif->background_index], gif->width * gif->height * sizeof(int)); */ } else if ((frame != 0) && (gif->frames[frame - 1].disposal_method == GIF_FRAME_CLEAR)) { clear_image = true; if ((return_value = gif_decode_frame(gif, (frame - 1))) != GIF_OK) @@ -890,7 +897,8 @@ gif_result gif_decode_frame(gif_animation *gif, unsigned int frame) { /* If we don't find one, clear the frame data */ if (last_undisposed_frame == -1) { - memset((char*)frame_data, colour_table[gif->background_index], gif->width * gif->height * sizeof(int)); + /* see notes above on transparency vs. background color */ + memset((char*)frame_data, GIF_TRANSPARENT_COLOUR, gif->width * gif->height * sizeof(int)); } else { if ((return_value = gif_decode_frame(gif, last_undisposed_frame)) != GIF_OK) goto gif_decode_frame_exit; |