diff options
Diffstat (limited to 'libavformat/gif.c')
| -rw-r--r-- | libavformat/gif.c | 28 |
1 files changed, 26 insertions, 2 deletions
diff --git a/libavformat/gif.c b/libavformat/gif.c index 3d86f23..f26d537 100644 --- a/libavformat/gif.c +++ b/libavformat/gif.c @@ -102,15 +102,39 @@ static int gif_write_header(AVFormatContext *s) static int gif_write_packet(AVFormatContext *s, AVPacket *pkt) { + int size; AVCodecContext *enc = s->streams[pkt->stream_index]->codec; AVIOContext *pb = s->pb; int jiffies; + uint8_t flags = 0x4, transparent_color_index = 0x1f; + const uint32_t *palette; + + /* Mark one colour as transparent if the input palette contains at least + * one colour that is more than 50% transparent. */ + palette = (uint32_t*)av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size); + if (palette && size != AVPALETTE_SIZE) { + av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n"); + return AVERROR_INVALIDDATA; + } + if (palette) { + unsigned i, smallest_alpha = 0xff; + + for (i = 0; i < AVPALETTE_COUNT; i++) { + const uint32_t v = palette[i]; + if (v >> 24 < smallest_alpha) { + smallest_alpha = v >> 24; + transparent_color_index = i; + } + } + if (smallest_alpha < 128) + flags |= 0x1; /* Transparent Color Flag */ + } /* graphic control extension block */ avio_w8(pb, 0x21); avio_w8(pb, 0xf9); avio_w8(pb, 0x04); /* block size */ - avio_w8(pb, 0x04); /* flags */ + avio_w8(pb, flags); /* 1 jiffy is 1/70 s */ /* the delay_time field indicates the number of jiffies - 1 */ @@ -121,7 +145,7 @@ static int gif_write_packet(AVFormatContext *s, AVPacket *pkt) avio_wl16(pb, jiffies); - avio_w8(pb, 0x1f); /* transparent color index */ + avio_w8(pb, transparent_color_index); avio_w8(pb, 0x00); avio_write(pb, pkt->data, pkt->size); |
