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* Copyright (c) 2000 Fabrice Bellard.
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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* First version by Francois Revol revol@free.fr
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* Features and limitations:
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* - currently no compression is performed,
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* in fact the size of the data is 9/8 the size of the image in 8bpp
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* - uses only a global standard palette
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* - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
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* Reference documents:
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* http://www.goice.co.jp/member/mo/formats/gif.html
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* http://astronomy.swin.edu.au/pbourke/dataformats/gif/
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* http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
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* this url claims to have an LZW algorithm not covered by Unisys patent:
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* http://www.msg.net/utility/whirlgif/gifencod.html
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* could help reduce the size of the files _a lot_...
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* some sites mentions an RLE type compression also.
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#include "bitstream.h"
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/* bitstream minipacket size */
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#define GIF_CHUNKS 100
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/* slows down the decoding (and some browsers don't like it) */
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/* update on the 'some browsers don't like it issue from above: this was probably due to missing 'Data Sub-block Terminator' (byte 19) in the app_header */
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#define GIF_ADD_APP_HEADER // required to enable looping of animated gif
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/* we use the standard 216 color palette */
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/* this script was used to create the palette:
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* for r in 00 33 66 99 cc ff; do for g in 00 33 66 99 cc ff; do echo -n " "; for b in 00 33 66 99 cc ff; do
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* echo -n "{ 0x$r, 0x$g, 0x$b }, "; done; echo ""; done; done
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static const rgb_triplet gif_clut[216] = {
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{ 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
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{ 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
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{ 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
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{ 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
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{ 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
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{ 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
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{ 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
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{ 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
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{ 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
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{ 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
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{ 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
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{ 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
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{ 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
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{ 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
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{ 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
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{ 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
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{ 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
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{ 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
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{ 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
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{ 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
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{ 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
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{ 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
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{ 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
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{ 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
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{ 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
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{ 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
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{ 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
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{ 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
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{ 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
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{ 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
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{ 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
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{ 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
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{ 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
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{ 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
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{ 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
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{ 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
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/* The GIF format uses reversed order for bitstreams... */
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/* at least they don't use PDP_ENDIAN :) */
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/* so we 'extend' PutBitContext. hmmm, OOP :) */
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/* seems this thing changed slightly since I wrote it... */
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#ifdef ALT_BITSTREAM_WRITER
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# error no ALT_BITSTREAM_WRITER support for now
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static void gif_put_bits_rev(PutBitContext *s, int n, unsigned int value)
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unsigned int bit_buf;
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st_out_bit_counts[st_current_index] += n;
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// printf("put_bits=%d %x\n", n, value);
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assert(n == 32 || value < (1U << n));
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bit_buf = s->bit_buf;
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bit_cnt = 32 - s->bit_left; /* XXX:lazyness... was = s->bit_cnt; */
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// printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
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if (n < (32-bit_cnt)) {
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bit_buf |= value << (bit_cnt);
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bit_buf |= value << (bit_cnt);
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*s->buf_ptr = bit_buf & 0xff;
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s->buf_ptr[1] = (bit_buf >> 8) & 0xff;
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s->buf_ptr[2] = (bit_buf >> 16) & 0xff;
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s->buf_ptr[3] = (bit_buf >> 24) & 0xff;
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//printf("bitbuf = %08x\n", bit_buf);
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if (s->buf_ptr >= s->buf_end)
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puts("bit buffer overflow !!"); // should never happen ! who got rid of the callback ???
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// flush_buffer_rev(s);
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bit_cnt=bit_cnt + n - 32;
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bit_buf = value >> (n - bit_cnt);
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s->bit_buf = bit_buf;
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s->bit_left = 32 - bit_cnt;
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/* pad the end of the output stream with zeros */
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static void gif_flush_put_bits_rev(PutBitContext *s)
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while (s->bit_left < 32) {
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/* XXX: should test end of buffer */
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*s->buf_ptr++=s->bit_buf & 0xff;
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// flush_buffer_rev(s);
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/* !RevPutBitContext */
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static int gif_image_write_header(ByteIOContext *pb,
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int width, int height, int loop_count,
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put_le16(pb, height);
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put_byte(pb, 0xf7); /* flags: global clut, 256 entries */
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put_byte(pb, 0x1f); /* background color index */
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put_byte(pb, 0); /* aspect ratio */
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/* the global palette */
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put_buffer(pb, (unsigned char *)gif_clut, 216*3);
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for(i=0;i<((256-216)*3);i++)
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put_byte(pb, (v >> 16) & 0xff);
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put_byte(pb, (v >> 8) & 0xff);
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put_byte(pb, (v) & 0xff);
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/* update: this is the 'NETSCAPE EXTENSION' that allows for looped animated gif
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see http://members.aol.com/royalef/gifabout.htm#net-extension
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byte 1 : 33 (hex 0x21) GIF Extension code
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byte 2 : 255 (hex 0xFF) Application Extension Label
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byte 3 : 11 (hex (0x0B) Length of Application Block
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(eleven bytes of data to follow)
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bytes 4 to 11 : "NETSCAPE"
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bytes 12 to 14 : "2.0"
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byte 15 : 3 (hex 0x03) Length of Data Sub-Block
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(three bytes of data to follow)
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byte 16 : 1 (hex 0x01)
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bytes 17 to 18 : 0 to 65535, an unsigned integer in
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lo-hi byte format. This indicate the
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number of iterations the loop should
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bytes 19 : 0 (hex 0x00) a Data Sub-block Terminator
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/* application extension header */
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#ifdef GIF_ADD_APP_HEADER
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if (loop_count >= 0 && loop_count <= 65535) {
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put_tag(pb, "NETSCAPE2.0"); // bytes 4 to 14
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put_byte(pb, 0x03); // byte 15
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put_byte(pb, 0x01); // byte 16
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put_le16(pb, (uint16_t)loop_count);
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put_byte(pb, 0x00); // byte 19
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/* this is maybe slow, but allows for extensions */
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static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
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return ((((r)/47)%6)*6*6+(((g)/47)%6)*6+(((b)/47)%6));
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static int gif_image_write_image(ByteIOContext *pb,
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int x1, int y1, int width, int height,
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const uint8_t *buf, int linesize, int pix_fmt)
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uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
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put_le16(pb, height);
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put_byte(pb, 0x00); /* flags */
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left= width * height;
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init_put_bits(&p, buffer, 130);
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* the thing here is the bitstream is written as little packets, with a size byte before
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* but it's still the same bitstream between packets (no flush !)
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gif_put_bits_rev(&p, 9, 0x0100); /* clear code */
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for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
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if (pix_fmt == PIX_FMT_RGB24) {
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v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
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gif_put_bits_rev(&p, 9, v);
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if(left<=GIF_CHUNKS) {
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gif_put_bits_rev(&p, 9, 0x101); /* end of stream */
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gif_flush_put_bits_rev(&p);
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if(pbBufPtr(&p) - p.buf > 0) {
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put_byte(pb, pbBufPtr(&p) - p.buf); /* byte count of the packet */
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put_buffer(pb, p.buf, pbBufPtr(&p) - p.buf); /* the actual buffer */
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p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
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put_byte(pb, 0x00); /* end of image block */
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int64_t time, file_time;
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uint8_t buffer[100]; /* data chunks */
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static int gif_write_header(AVFormatContext *s)
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GIFContext *gif = s->priv_data;
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ByteIOContext *pb = &s->pb;
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AVCodecContext *enc, *video_enc;
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int i, width, height, loop_count /*, rate*/;
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/* XXX: do we reject audio streams or just ignore them ?
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if(s->nb_streams > 1)
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for(i=0;i<s->nb_streams;i++) {
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enc = s->streams[i]->codec;
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if (enc->codec_type != CODEC_TYPE_AUDIO)
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width = video_enc->width;
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height = video_enc->height;
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loop_count = s->loop_output;
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// rate = video_enc->time_base.den;
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/* XXX: is it allowed ? seems to work so far... */
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video_enc->pix_fmt = PIX_FMT_RGB24;
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gif_image_write_header(pb, width, height, loop_count, NULL);
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put_flush_packet(&s->pb);
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static int gif_write_video(AVFormatContext *s,
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AVCodecContext *enc, const uint8_t *buf, int size)
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ByteIOContext *pb = &s->pb;
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GIFContext *gif = s->priv_data;
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/* graphic control extension block */
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put_byte(pb, 0x04); /* block size */
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put_byte(pb, 0x04); /* flags */
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/* 1 jiffy is 1/70 s */
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/* the delay_time field indicates the number of jiffies - 1 */
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delay = gif->file_time - gif->time;
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/* XXX: should use delay, in order to be more accurate */
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/* instead of using the same rounded value each time */
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/* XXX: don't even remember if I really use it for now */
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jiffies = (70*enc->time_base.num/enc->time_base.den) - 1;
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put_le16(pb, jiffies);
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put_byte(pb, 0x1f); /* transparent color index */
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gif_image_write_image(pb, 0, 0, enc->width, enc->height,
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buf, enc->width * 3, PIX_FMT_RGB24);
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put_flush_packet(&s->pb);
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static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
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AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
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if (codec->codec_type == CODEC_TYPE_AUDIO)
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return 0; /* just ignore audio */
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return gif_write_video(s, codec, pkt->data, pkt->size);
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static int gif_write_trailer(AVFormatContext *s)
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ByteIOContext *pb = &s->pb;
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put_flush_packet(&s->pb);
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/* better than nothing gif image writer */
408
int gif_write(ByteIOContext *pb, AVImageInfo *info)
410
gif_image_write_header(pb, info->width, info->height, AVFMT_NOOUTPUTLOOP,
411
(uint32_t *)info->pict.data[1]);
412
gif_image_write_image(pb, 0, 0, info->width, info->height,
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info->pict.data[0], info->pict.linesize[0],
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put_flush_packet(pb);
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static AVOutputFormat gif_oformat = {
433
extern AVInputFormat gif_iformat;
437
av_register_output_format(&gif_oformat);
438
av_register_input_format(&gif_iformat);
added
removed
libavformat/gif.c
