Fix writing transparent GIFs

aaaaaa123456789 · Jan 31, 2022 · beb60b4 · beb60b4
1 parent 309edf0
commit beb60b4
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diff --git a/docs/changelog.md b/docs/changelog.md
@@ -5,6 +5,7 @@ Note: releases are listed from latest to oldest.
 ## Version 1.0 (in development)
 
 - Fixed a bug when loading APNG files with reduced frames
+- Fixed emitting GIF files with transparent pixels
 - Fixed a bug in the GIF compressor that would generate invalid compressed frame data when a code size increase and
   reduction occured at the same time
 - Fixed a file descriptor leak that would keep an open `FILE *` if a `PLUM_ERR_FILE_ERROR` error was raised while

diff --git a/src/gifwrite.c b/src/gifwrite.c
@@ -166,7 +166,7 @@ void generate_GIF_frame_data (struct context * context, uint32_t * restrict pixe
   int transparent_index = -1;
   if (transparent)
     for (index = 0; index <= colorcount; index ++) if (palette[index] == transparent) {
-      transparent_index = transparent;
+      transparent_index = index;
       break;
     }
   write_GIF_frame(context, framebuffer, palette, colorcount + 1, transparent_index, frame, left, top, width, height, durations, disposals);