1/*
2 * GIF decoder
3 * Copyright (c) 2003 Fabrice Bellard
4 * Copyright (c) 2006 Baptiste Coudurier
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23//#define DEBUG
24
25#include "avcodec.h"
26#include "bytestream.h"
27#include "lzw.h"
28
29#define GCE_DISPOSAL_NONE       0
30#define GCE_DISPOSAL_INPLACE    1
31#define GCE_DISPOSAL_BACKGROUND 2
32#define GCE_DISPOSAL_RESTORE    3
33
34typedef struct GifState {
35    AVFrame picture;
36    int screen_width;
37    int screen_height;
38    int bits_per_pixel;
39    int background_color_index;
40    int transparent_color_index;
41    int color_resolution;
42    uint32_t *image_palette;
43
44    /* after the frame is displayed, the disposal method is used */
45    int gce_disposal;
46    /* delay during which the frame is shown */
47    int gce_delay;
48
49    /* LZW compatible decoder */
50    const uint8_t *bytestream;
51    const uint8_t *bytestream_end;
52    LZWState *lzw;
53
54    /* aux buffers */
55    uint8_t global_palette[256 * 3];
56    uint8_t local_palette[256 * 3];
57
58  AVCodecContext* avctx;
59} GifState;
60
61static const uint8_t gif87a_sig[6] = "GIF87a";
62static const uint8_t gif89a_sig[6] = "GIF89a";
63
64static int gif_read_image(GifState *s)
65{
66    int left, top, width, height, bits_per_pixel, code_size, flags;
67    int is_interleaved, has_local_palette, y, pass, y1, linesize, n, i;
68    uint8_t *ptr, *spal, *palette, *ptr1;
69
70    left = bytestream_get_le16(&s->bytestream);
71    top = bytestream_get_le16(&s->bytestream);
72    width = bytestream_get_le16(&s->bytestream);
73    height = bytestream_get_le16(&s->bytestream);
74    flags = bytestream_get_byte(&s->bytestream);
75    is_interleaved = flags & 0x40;
76    has_local_palette = flags & 0x80;
77    bits_per_pixel = (flags & 0x07) + 1;
78#ifdef DEBUG
79    dprintf(s->avctx, "gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
80#endif
81
82    if (has_local_palette) {
83        bytestream_get_buffer(&s->bytestream, s->local_palette, 3 * (1 << bits_per_pixel));
84        palette = s->local_palette;
85    } else {
86        palette = s->global_palette;
87        bits_per_pixel = s->bits_per_pixel;
88    }
89
90    /* verify that all the image is inside the screen dimensions */
91    if (left + width > s->screen_width ||
92        top + height > s->screen_height)
93        return AVERROR(EINVAL);
94
95    /* build the palette */
96    n = (1 << bits_per_pixel);
97    spal = palette;
98    for(i = 0; i < n; i++) {
99        s->image_palette[i] = (0xff << 24) | AV_RB24(spal);
100        spal += 3;
101    }
102    for(; i < 256; i++)
103        s->image_palette[i] = (0xff << 24);
104    /* handle transparency */
105    if (s->transparent_color_index >= 0)
106        s->image_palette[s->transparent_color_index] = 0;
107
108    /* now get the image data */
109    code_size = bytestream_get_byte(&s->bytestream);
110    ff_lzw_decode_init(s->lzw, code_size, s->bytestream,
111                       s->bytestream_end - s->bytestream, FF_LZW_GIF);
112
113    /* read all the image */
114    linesize = s->picture.linesize[0];
115    ptr1 = s->picture.data[0] + top * linesize + left;
116    ptr = ptr1;
117    pass = 0;
118    y1 = 0;
119    for (y = 0; y < height; y++) {
120        ff_lzw_decode(s->lzw, ptr, width);
121        if (is_interleaved) {
122            switch(pass) {
123            default:
124            case 0:
125            case 1:
126                y1 += 8;
127                ptr += linesize * 8;
128                if (y1 >= height) {
129                    y1 = pass ? 2 : 4;
130                    ptr = ptr1 + linesize * y1;
131                    pass++;
132                }
133                break;
134            case 2:
135                y1 += 4;
136                ptr += linesize * 4;
137                if (y1 >= height) {
138                    y1 = 1;
139                    ptr = ptr1 + linesize;
140                    pass++;
141                }
142                break;
143            case 3:
144                y1 += 2;
145                ptr += linesize * 2;
146                break;
147            }
148        } else {
149            ptr += linesize;
150        }
151    }
152    /* read the garbage data until end marker is found */
153    ff_lzw_decode_tail(s->lzw);
154    s->bytestream = ff_lzw_cur_ptr(s->lzw);
155    return 0;
156}
157
158static int gif_read_extension(GifState *s)
159{
160    int ext_code, ext_len, i, gce_flags, gce_transparent_index;
161
162    /* extension */
163    ext_code = bytestream_get_byte(&s->bytestream);
164    ext_len = bytestream_get_byte(&s->bytestream);
165#ifdef DEBUG
166    dprintf(s->avctx, "gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
167#endif
168    switch(ext_code) {
169    case 0xf9:
170        if (ext_len != 4)
171            goto discard_ext;
172        s->transparent_color_index = -1;
173        gce_flags = bytestream_get_byte(&s->bytestream);
174        s->gce_delay = bytestream_get_le16(&s->bytestream);
175        gce_transparent_index = bytestream_get_byte(&s->bytestream);
176        if (gce_flags & 0x01)
177            s->transparent_color_index = gce_transparent_index;
178        else
179            s->transparent_color_index = -1;
180        s->gce_disposal = (gce_flags >> 2) & 0x7;
181#ifdef DEBUG
182        dprintf(s->avctx, "gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
183               gce_flags, s->gce_delay,
184               s->transparent_color_index, s->gce_disposal);
185#endif
186        ext_len = bytestream_get_byte(&s->bytestream);
187        break;
188    }
189
190    /* NOTE: many extension blocks can come after */
191 discard_ext:
192    while (ext_len != 0) {
193        for (i = 0; i < ext_len; i++)
194            bytestream_get_byte(&s->bytestream);
195        ext_len = bytestream_get_byte(&s->bytestream);
196#ifdef DEBUG
197        dprintf(s->avctx, "gif: ext_len1=%d\n", ext_len);
198#endif
199    }
200    return 0;
201}
202
203static int gif_read_header1(GifState *s)
204{
205    uint8_t sig[6];
206    int v, n;
207    int has_global_palette;
208
209    if (s->bytestream_end < s->bytestream + 13)
210        return -1;
211
212    /* read gif signature */
213    bytestream_get_buffer(&s->bytestream, sig, 6);
214    if (memcmp(sig, gif87a_sig, 6) != 0 &&
215        memcmp(sig, gif89a_sig, 6) != 0)
216        return -1;
217
218    /* read screen header */
219    s->transparent_color_index = -1;
220    s->screen_width = bytestream_get_le16(&s->bytestream);
221    s->screen_height = bytestream_get_le16(&s->bytestream);
222    if(   (unsigned)s->screen_width  > 32767
223       || (unsigned)s->screen_height > 32767){
224        av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
225        return -1;
226    }
227
228    v = bytestream_get_byte(&s->bytestream);
229    s->color_resolution = ((v & 0x70) >> 4) + 1;
230    has_global_palette = (v & 0x80);
231    s->bits_per_pixel = (v & 0x07) + 1;
232    s->background_color_index = bytestream_get_byte(&s->bytestream);
233    bytestream_get_byte(&s->bytestream);                /* ignored */
234#ifdef DEBUG
235    dprintf(s->avctx, "gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
236           s->screen_width, s->screen_height, s->bits_per_pixel,
237           has_global_palette);
238#endif
239    if (has_global_palette) {
240        n = 1 << s->bits_per_pixel;
241        if (s->bytestream_end < s->bytestream + n * 3)
242            return -1;
243        bytestream_get_buffer(&s->bytestream, s->global_palette, n * 3);
244    }
245    return 0;
246}
247
248static int gif_parse_next_image(GifState *s)
249{
250    while (s->bytestream < s->bytestream_end) {
251        int code = bytestream_get_byte(&s->bytestream);
252#ifdef DEBUG
253        dprintf(s->avctx, "gif: code=%02x '%c'\n", code, code);
254#endif
255        switch (code) {
256        case ',':
257            return gif_read_image(s);
258        case '!':
259            if (gif_read_extension(s) < 0)
260                return -1;
261            break;
262        case ';':
263            /* end of image */
264        default:
265            /* error or erroneous EOF */
266            return -1;
267        }
268    }
269    return -1;
270}
271
272static av_cold int gif_decode_init(AVCodecContext *avctx)
273{
274    GifState *s = avctx->priv_data;
275
276    s->avctx = avctx;
277
278    avcodec_get_frame_defaults(&s->picture);
279    avctx->coded_frame= &s->picture;
280    s->picture.data[0] = NULL;
281    ff_lzw_decode_open(&s->lzw);
282    return 0;
283}
284
285static int gif_decode_frame(AVCodecContext *avctx, void *data, int *data_size, AVPacket *avpkt)
286{
287    const uint8_t *buf = avpkt->data;
288    int buf_size = avpkt->size;
289    GifState *s = avctx->priv_data;
290    AVFrame *picture = data;
291    int ret;
292
293    s->bytestream = buf;
294    s->bytestream_end = buf + buf_size;
295    if (gif_read_header1(s) < 0)
296        return -1;
297
298    avctx->pix_fmt = PIX_FMT_PAL8;
299    if (avcodec_check_dimensions(avctx, s->screen_width, s->screen_height))
300        return -1;
301    avcodec_set_dimensions(avctx, s->screen_width, s->screen_height);
302
303    if (s->picture.data[0])
304        avctx->release_buffer(avctx, &s->picture);
305    if (avctx->get_buffer(avctx, &s->picture) < 0) {
306        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
307        return -1;
308    }
309    s->image_palette = (uint32_t *)s->picture.data[1];
310    ret = gif_parse_next_image(s);
311    if (ret < 0)
312        return ret;
313
314    *picture = s->picture;
315    *data_size = sizeof(AVPicture);
316    return s->bytestream - buf;
317}
318
319static av_cold int gif_decode_close(AVCodecContext *avctx)
320{
321    GifState *s = avctx->priv_data;
322
323    ff_lzw_decode_close(&s->lzw);
324    if(s->picture.data[0])
325        avctx->release_buffer(avctx, &s->picture);
326    return 0;
327}
328
329AVCodec gif_decoder = {
330    "gif",
331    AVMEDIA_TYPE_VIDEO,
332    CODEC_ID_GIF,
333    sizeof(GifState),
334    gif_decode_init,
335    NULL,
336    gif_decode_close,
337    gif_decode_frame,
338    CODEC_CAP_DR1,
339    .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
340};
341