[FFmpeg-devel] fix for transparencies in animated gifs (requires feedback)

Message ID	20171024164022.64121-1-bjorn@giphy.com
State	New
Headers	show Delivered-To: ffmpegpatchwork@gmail.com Received-SPF: pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) client-ip=79.124.17.100; From: Bjorn Roche <bjorn@giphy.com> To: ffmpeg-devel@ffmpeg.org Date: Tue, 24 Oct 2017 12:40:22 -0400 Message-Id: <20171024164022.64121-1-bjorn@giphy.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH] fix for transparencies in animated gifs (requires feedback) Precedence: list Reply-To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org> Cc: Bjorn Roche <bjorn@giphy.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" <ffmpeg-devel-bounces@ffmpeg.org>

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h index 52cc5b0ca0..82a5328ce1 100644 --- a/libavcodec/avcodec.h +++ b/libavcodec/avcodec.h @@ -1599,6 +1599,12 @@ enum AVPacketSideDataType { */ AV_PKT_DATA_CONTENT_LIGHT_LEVEL, + /** + * The disposal method that should be used with the frame. If missing, + * the frame will not be disposed. This contains exactly one byte. + */ + AV_PKT_DATA_GIF_FRAME_DISPOSAL, + /** * ATSC A53 Part 4 Closed Captions. This metadata should be associated with * a video stream. A53 CC bitstream is stored as uint8_t in AVPacketSideData.data. diff --git a/libavcodec/gif.c b/libavcodec/gif.c index d9c99d52cf..6c839d99d2 100644 --- a/libavcodec/gif.c +++ b/libavcodec/gif.c @@ -74,11 +74,35 @@ static int pick_palette_entry(const uint8_t *buf, int linesize, int w, int h) return -1; } -static int gif_image_write_image(AVCodecContext *avctx, - uint8_t **bytestream, uint8_t *end, - const uint32_t *palette, - const uint8_t *buf, const int linesize, - AVPacket *pkt) +// returns true if any of the pixels are transparent +static int is_image_translucent(AVCodecContext *avctx, + const uint32_t *palette, + const uint8_t *buf, const int linesize) +{ + GIFContext *s = avctx->priv_data; + int trans = s->transparent_index; + int p; + const int m = avctx->width * avctx->height ; + + if (trans < 0) { + return 0; + } + + for (p=0; p<m; ++p) { + if (buf[p] == trans) { + return 1; + } + } + return 0; +} + +// writes an opaque image. ie an image with no transparency. +// it also works, and should be used, for a first image. +static int gif_image_write_opaque(AVCodecContext *avctx, + uint8_t **bytestream, uint8_t *end, + const uint32_t *palette, + const uint8_t *buf, const int linesize, + AVPacket *pkt) { GIFContext *s = avctx->priv_data; int len = 0, height = avctx->height, width = avctx->width, x, y; @@ -137,6 +161,11 @@ static int gif_image_write_image(AVCodecContext *avctx, width, height, x_start, y_start, avctx->width, avctx->height); } + uint8_t *frame_disposal = av_packet_new_side_data(pkt, AV_PKT_DATA_GIF_FRAME_DISPOSAL, 1); + if (!frame_disposal) + return AVERROR(ENOMEM); + *frame_disposal = GCE_DISPOSAL_INPLACE; + /* image block */ bytestream_put_byte(bytestream, GIF_IMAGE_SEPARATOR); bytestream_put_le16(bytestream, x_start); @@ -214,6 +243,163 @@ static int gif_image_write_image(AVCodecContext *avctx, return 0; } +// wrtites an image that may contain transparency +// this should work for opaque images as well, but will be less optimized. +static int gif_image_write_translucent(AVCodecContext *avctx, + uint8_t **bytestream, uint8_t *end, + const uint32_t *palette, + const uint8_t *buf, const int linesize, + AVPacket *pkt) +{ + GIFContext *s = avctx->priv_data; + int len = 0, height = avctx->height, width = avctx->width, y; + int x_start = 0, y_start = 0, trans = s->transparent_index; + const uint8_t *ptr; + + /* Crop Image */ + if ((s->flags & GF_OFFSETTING) && trans >=0) { + const int w = avctx->width; + const int h = avctx->height; + int x_end = w - 1, + y_end = h - 1; + + // crop top + while (y_start < y_end) { + int i; + int is_trans = 1; + for (i=0; i<w; ++i) { + if( buf[w*y_start+i] != trans ) { + is_trans = 0; + break; + } + } + if (!is_trans) + break; + y_start++; + } + + // crop bottom + while (y_end < h) { + int i; + int is_trans = 1; + for (i=0; i<w; ++i) { + if (buf[w*y_end+i] != trans) { + is_trans = 0; + break; + } + } + if (!is_trans) + break; + y_end--; + } + + // crop left + while (x_start < x_end) { + int i; + int is_trans = 1; + for (i=y_start; i<y_end; ++i) { + if (buf[w*i+x_start] != trans) { + is_trans = 0; + break; + } + } + if (!is_trans) + break; + x_start++; + } + + // crop right + while (x_end < w) { + int i; + int is_trans = 1; + for (i=y_start; i<y_end; ++i) { + if (buf[w*i+x_end] != trans) { + is_trans = 0; + break; + } + } + if (!is_trans) + break; + x_end--; + } + + height = y_end + 1 - y_start; + width = x_end + 1 - x_start; + av_log(avctx, AV_LOG_DEBUG,"%dx%d image at pos (%d;%d) [area:%dx%d]\n", + width, height, x_start, y_start, avctx->width, avctx->height); + } + + + uint8_t *frame_disposal = av_packet_new_side_data(pkt, AV_PKT_DATA_GIF_FRAME_DISPOSAL, 1); + if (!frame_disposal) + return AVERROR(ENOMEM); + *frame_disposal = GCE_DISPOSAL_BACKGROUND; + + /* image block */ + bytestream_put_byte(bytestream, GIF_IMAGE_SEPARATOR); + bytestream_put_le16(bytestream, x_start); + bytestream_put_le16(bytestream, y_start); + bytestream_put_le16(bytestream, width); + bytestream_put_le16(bytestream, height); + + if (!palette) { + bytestream_put_byte(bytestream, 0x00); /* flags */ + } else { + unsigned i; + bytestream_put_byte(bytestream, 1<<7 | 0x7); /* flags */ + for (i = 0; i < AVPALETTE_COUNT; i++) { + const uint32_t v = palette[i]; + bytestream_put_be24(bytestream, v); + } + } + + bytestream_put_byte(bytestream, 0x08); + + ff_lzw_encode_init(s->lzw, s->buf, s->buf_size, + 12, FF_LZW_GIF, put_bits); + + ptr = buf + y_start*linesize + x_start; + + for (y = 0; y < height; y++) { + len += ff_lzw_encode(s->lzw, ptr, width); + ptr += linesize; + } + + len += ff_lzw_encode_flush(s->lzw, flush_put_bits); + + ptr = s->buf; + while (len > 0) { + int size = FFMIN(255, len); + bytestream_put_byte(bytestream, size); + if (end - *bytestream < size) + return -1; + bytestream_put_buffer(bytestream, ptr, size); + ptr += size; + len -= size; + } + bytestream_put_byte(bytestream, 0x00); /* end of image block */ + + return 0; +} + +static int gif_image_write_image(AVCodecContext *avctx, + uint8_t **bytestream, uint8_t *end, + const uint32_t *palette, + const uint8_t *buf, const int linesize, + AVPacket *pkt) +{ + GIFContext *s = avctx->priv_data; + if (!s->last_frame) { + return gif_image_write_opaque(avctx, bytestream, end, palette, buf, linesize, pkt); + } + + if (is_image_translucent(avctx, palette, buf, linesize)) { + return gif_image_write_translucent(avctx, bytestream, end, palette, buf, linesize, pkt); + } else { + return gif_image_write_opaque(avctx, bytestream, end, palette, buf, linesize, pkt); + } +} + static av_cold int gif_encode_init(AVCodecContext *avctx) { GIFContext *s = avctx->priv_data; diff --git a/libavformat/gif.c b/libavformat/gif.c index 01d98a27b0..b4a8b6aa94 100644 --- a/libavformat/gif.c +++ b/libavformat/gif.c @@ -144,6 +144,8 @@ static int flush_packet(AVFormatContext *s, AVPacket *new) AVIOContext *pb = s->pb; const uint32_t *palette; AVPacket *pkt = gif->prev_pkt; + uint8_t *disposal; + uint8_t packed; if (!pkt) return 0; @@ -157,16 +159,28 @@ static int flush_packet(AVFormatContext *s, AVPacket *new) } bcid = get_palette_transparency_index(palette); + disposal = av_packet_get_side_data(pkt, AV_PKT_DATA_GIF_FRAME_DISPOSAL, &size); + if (disposal && size != 1) { + av_log(s, AV_LOG_ERROR, "Invalid gif frame disposal extradata\n"); + return AVERROR_INVALIDDATA; + } + if (new && new->pts != AV_NOPTS_VALUE) gif->duration = av_clip_uint16(new->pts - gif->prev_pkt->pts); else if (!new && gif->last_delay >= 0) gif->duration = gif->last_delay; /* graphic control extension block */ + if (disposal) { + packed = (0xff & (*disposal)<<2) | (bcid >= 0); + } else { + packed = 1<<2 | (bcid >= 0); + } + avio_w8(pb, 0x21); avio_w8(pb, 0xf9); avio_w8(pb, 0x04); /* block size */ - avio_w8(pb, 1<<2 | (bcid >= 0)); + avio_w8(pb, packed); avio_wl16(pb, gif->duration); avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid); avio_w8(pb, 0x00);

[FFmpeg-devel] fix for transparencies in animated gifs (requires feedback)

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