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LZW decoder as separate module plus TIFF LZW support

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Originally committed as revision 6795 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Kostya Shishkov
2006-10-26 04:15:48 +00:00
parent b0c32a70b4
commit ffc5430bc3
6 changed files with 342 additions and 174 deletions
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176
libavcodec/gifdec.c
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@ -24,9 +24,7 @@
#include "avcodec.h"
#include "bytestream.h"
#define MAXBITS 12
#define SIZTABLE (1<<MAXBITS)
#include "lzw.h"
#define GCE_DISPOSAL_NONE 0
#define GCE_DISPOSAL_INPLACE 1
@ -50,175 +48,16 @@ typedef struct GifState {
/* LZW compatible decoder */
uint8_t *bytestream;
int eob_reached;
uint8_t *pbuf, *ebuf;
int bbits;
unsigned int bbuf;
int cursize; /* The current code size */
int curmask;
int codesize;
int clear_code;
int end_code;
int newcodes; /* First available code */
int top_slot; /* Highest code for current size */
int slot; /* Last read code */
int fc, oc;
uint8_t *sp;
uint8_t stack[SIZTABLE];
uint8_t suffix[SIZTABLE];
uint16_t prefix[SIZTABLE];
LZWState *lzw;
/* aux buffers */
uint8_t global_palette[256 * 3];
uint8_t local_palette[256 * 3];
uint8_t buf[256];
} GifState;
static const uint8_t gif87a_sig[6] = "GIF87a";
static const uint8_t gif89a_sig[6] = "GIF89a";
static const uint16_t mask[17] =
{
0x0000, 0x0001, 0x0003, 0x0007,
0x000F, 0x001F, 0x003F, 0x007F,
0x00FF, 0x01FF, 0x03FF, 0x07FF,
0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF
};
static void GLZWDecodeInit(GifState * s, int csize)
{
/* read buffer */
s->eob_reached = 0;
s->pbuf = s->buf;
s->ebuf = s->buf;
s->bbuf = 0;
s->bbits = 0;
/* decoder */
s->codesize = csize;
s->cursize = s->codesize + 1;
s->curmask = mask[s->cursize];
s->top_slot = 1 << s->cursize;
s->clear_code = 1 << s->codesize;
s->end_code = s->clear_code + 1;
s->slot = s->newcodes = s->clear_code + 2;
s->oc = s->fc = 0;
s->sp = s->stack;
}
/* XXX: optimize */
static inline int GetCode(GifState * s)
{
int c, sizbuf;
uint8_t *ptr;
while (s->bbits < s->cursize) {
ptr = s->pbuf;
if (ptr >= s->ebuf) {
if (!s->eob_reached) {
sizbuf = bytestream_get_byte(&s->bytestream);
s->ebuf = s->buf + sizbuf;
s->pbuf = s->buf;
if (sizbuf > 0) {
bytestream_get_buffer(&s->bytestream, s->buf, sizbuf);
} else {
s->eob_reached = 1;
}
}
ptr = s->pbuf;
}
s->bbuf |= ptr[0] << s->bbits;
ptr++;
s->pbuf = ptr;
s->bbits += 8;
}
c = s->bbuf & s->curmask;
s->bbuf >>= s->cursize;
s->bbits -= s->cursize;
return c;
}
/* NOTE: the algorithm here is inspired from the LZW GIF decoder
written by Steven A. Bennett in 1987. */
/* return the number of byte decoded */
static int GLZWDecode(GifState * s, uint8_t * buf, int len)
{
int l, c, code, oc, fc;
uint8_t *sp;
if (s->end_code < 0)
return 0;
l = len;
sp = s->sp;
oc = s->oc;
fc = s->fc;
while (sp > s->stack) {
*buf++ = *(--sp);
if ((--l) == 0)
goto the_end;
}
for (;;) {
c = GetCode(s);
if (c == s->end_code) {
s->end_code = -1;
break;
} else if (c == s->clear_code) {
s->cursize = s->codesize + 1;
s->curmask = mask[s->cursize];
s->slot = s->newcodes;
s->top_slot = 1 << s->cursize;
while ((c = GetCode(s)) == s->clear_code);
if (c == s->end_code) {
s->end_code = -1;
break;
}
/* test error */
if (c >= s->slot)
c = 0;
fc = oc = c;
*buf++ = c;
if ((--l) == 0)
break;
} else {
code = c;
if (code >= s->slot) {
*sp++ = fc;
code = oc;
}
while (code >= s->newcodes) {
*sp++ = s->suffix[code];
code = s->prefix[code];
}
*sp++ = code;
if (s->slot < s->top_slot) {
s->suffix[s->slot] = fc = code;
s->prefix[s->slot++] = oc;
oc = c;
}
if (s->slot >= s->top_slot) {
if (s->cursize < MAXBITS) {
s->top_slot <<= 1;
s->curmask = mask[++s->cursize];
}
}
while (sp > s->stack) {
*buf++ = *(--sp);
if ((--l) == 0)
goto the_end;
}
}
}
the_end:
s->sp = sp;
s->oc = oc;
s->fc = fc;
return len - l;
}
static int gif_read_image(GifState *s)
{
int left, top, width, height, bits_per_pixel, code_size, flags;
@ -267,7 +106,8 @@ static int gif_read_image(GifState *s)
/* now get the image data */
code_size = bytestream_get_byte(&s->bytestream);
GLZWDecodeInit(s, code_size);
//TODO: add proper data size
ff_lzw_decode_init(s->lzw, code_size, s->bytestream, 0, FF_LZW_GIF);
/* read all the image */
linesize = s->picture.linesize[0];
@ -276,7 +116,7 @@ static int gif_read_image(GifState *s)
pass = 0;
y1 = 0;
for (y = 0; y < height; y++) {
GLZWDecode(s, ptr, width);
ff_lzw_decode(s->lzw, ptr, width);
if (is_interleaved) {
switch(pass) {
default:
@ -314,8 +154,8 @@ static int gif_read_image(GifState *s)
av_free(line);
/* read the garbage data until end marker is found */
while (!s->eob_reached)
GetCode(s);
ff_lzw_decode_tail(s->lzw);
s->bytestream = ff_lzw_cur_ptr(s->lzw);
return 0;
}
@ -445,6 +285,7 @@ static int gif_decode_init(AVCodecContext *avctx)
avcodec_get_frame_defaults(&s->picture);
avctx->coded_frame= &s->picture;
s->picture.data[0] = NULL;
ff_lzw_decode_open(&s->lzw);
return 0;
}
@ -483,6 +324,7 @@ static int gif_decode_close(AVCodecContext *avctx)
{
GifState *s = avctx->priv_data;
ff_lzw_decode_close(&s->lzw);
if(s->picture.data[0])
avctx->release_buffer(avctx, &s->picture);
return 0;