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png filters 

Originally committed as revision 12195 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Loren Merritt 2008-02-25 10:34:23 +00:00
parent e281d6844b
commit 4a5b619df7
2 changed files with 140 additions and 25 deletions
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1
libavcodec/png.h
View File

@ -39,6 +39,7 @@
#define PNG_FILTER_VALUE_UP 2
#define PNG_FILTER_VALUE_AVG 3
#define PNG_FILTER_VALUE_PAETH 4
#define PNG_FILTER_VALUE_MIXED 5
#define PNG_IHDR 0x0001
#define PNG_IDAT 0x0002

164
libavcodec/pngenc.c
View File

@ -21,10 +21,10 @@
#include "avcodec.h"
#include "bytestream.h"
#include "png.h"
#include <dsputil.h>
/* TODO:
* - add 2, 4 and 16 bit depth support
* - use filters when generating a png (better compression)
*/
#include <zlib.h>
@ -34,11 +34,15 @@
#define IOBUF_SIZE 4096
typedef struct PNGEncContext {
DSPContext dsp;
uint8_t *bytestream;
uint8_t *bytestream_start;
uint8_t *bytestream_end;
AVFrame picture;
int filter_type;
z_stream zstream;
uint8_t buf[IOBUF_SIZE];
} PNGEncContext;
@ -81,6 +85,93 @@ static void png_get_interlaced_row(uint8_t *dst, int row_size,
}
}
static void sub_png_paeth_prediction(uint8_t *dst, uint8_t *src, uint8_t *top, int w, int bpp)
{
int i;
for(i = 0; i < w; i++) {
int a, b, c, p, pa, pb, pc;
a = src[i - bpp];
b = top[i];
c = top[i - bpp];
p = b - c;
pc = a - c;
pa = abs(p);
pb = abs(pc);
pc = abs(p + pc);
if (pa <= pb && pa <= pc)
p = a;
else if (pb <= pc)
p = b;
else
p = c;
dst[i] = src[i] - p;
}
}
static void png_filter_row(DSPContext *dsp, uint8_t *dst, int filter_type,
uint8_t *src, uint8_t *top, int size, int bpp)
{
int i;
switch(filter_type) {
case PNG_FILTER_VALUE_NONE:
memcpy(dst, src, size);
break;
case PNG_FILTER_VALUE_SUB:
dsp->diff_bytes(dst, src, src-bpp, size);
memcpy(dst, src, bpp);
break;
case PNG_FILTER_VALUE_UP:
dsp->diff_bytes(dst, src, top, size);
break;
case PNG_FILTER_VALUE_AVG:
for(i = 0; i < bpp; i++)
dst[i] = src[i] - (top[i] >> 1);
for(; i < size; i++)
dst[i] = src[i] - ((src[i-bpp] + top[i]) >> 1);
break;
case PNG_FILTER_VALUE_PAETH:
for(i = 0; i < bpp; i++)
dst[i] = src[i] - top[i];
sub_png_paeth_prediction(dst+i, src+i, top+i, size-i, bpp);
break;
}
}
static uint8_t *png_choose_filter(PNGEncContext *s, uint8_t *dst,
uint8_t *src, uint8_t *top, int size, int bpp)
{
int pred = s->filter_type;
assert(bpp || !pred);
if(!top && pred)
pred = PNG_FILTER_VALUE_SUB;
if(pred == PNG_FILTER_VALUE_MIXED) {
int i;
int cost, bcost = INT_MAX;
uint8_t *buf1 = dst, *buf2 = dst + size + 16;
for(pred=0; pred<5; pred++) {
png_filter_row(&s->dsp, buf1+1, pred, src, top, size, bpp);
buf1[0] = pred;
cost = 0;
for(i=0; i<=size; i++)
cost += abs(0x80 - (buf1[i] ^ 0x80));
if(cost < bcost) {
bcost = cost;
FFSWAP(uint8_t*, buf1, buf2);
}
}
return buf2;
} else {
png_filter_row(&s->dsp, dst+1, pred, src, top, size, bpp);
dst[0] = pred;
return dst;
}
}
static void convert_from_rgb32(uint8_t *dst, const uint8_t *src, int width)
{
uint8_t *d;
@ -145,9 +236,11 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size,
int bit_depth, color_type, y, len, row_size, ret, is_progressive;
int bits_per_pixel, pass_row_size;
int compression_level;
uint8_t *ptr;
uint8_t *crow_buf = NULL;
uint8_t *tmp_buf = NULL;
uint8_t *ptr, *top;
uint8_t *crow_base = NULL, *crow_buf, *crow;
uint8_t *progressive_buf = NULL;
uint8_t *rgba_buf = NULL;
uint8_t *top_buf = NULL;
*p = *pict;
p->pict_type= FF_I_TYPE;
@ -195,12 +288,23 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size,
Z_DEFLATED, 15, 8, Z_DEFAULT_STRATEGY);
if (ret != Z_OK)
return -1;
crow_buf = av_malloc(row_size + 1);
if (!crow_buf)
crow_base = av_malloc((row_size + 32) << (s->filter_type == PNG_FILTER_VALUE_MIXED));
if (!crow_base)
goto fail;
crow_buf = crow_base + 15; // pixel data should be aligned, but there's a control byte before it
if (is_progressive) {
tmp_buf = av_malloc(row_size + 1);
if (!tmp_buf)
progressive_buf = av_malloc(row_size + 1);
if (!progressive_buf)
goto fail;
}
if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
rgba_buf = av_malloc(row_size + 1);
if (!rgba_buf)
goto fail;
}
if (is_progressive || color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
top_buf = av_malloc(row_size + 1);
if (!top_buf)
goto fail;
}
@ -247,7 +351,6 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size,
s->zstream.avail_out = IOBUF_SIZE;
s->zstream.next_out = s->buf;
if (is_progressive) {
uint8_t *ptr1;
int pass;
for(pass = 0; pass < NB_PASSES; pass++) {
@ -255,33 +358,37 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size,
output */
pass_row_size = ff_png_pass_row_size(pass, bits_per_pixel, avctx->width);
if (pass_row_size > 0) {
top = NULL;
for(y = 0; y < avctx->height; y++) {
if ((ff_png_pass_ymask[pass] << (y & 7)) & 0x80) {
ptr = p->data[0] + y * p->linesize[0];
FFSWAP(uint8_t*, progressive_buf, top_buf);
if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
convert_from_rgb32(tmp_buf, ptr, avctx->width);
ptr1 = tmp_buf;
} else {
ptr1 = ptr;
convert_from_rgb32(rgba_buf, ptr, avctx->width);
ptr = rgba_buf;
}
png_get_interlaced_row(crow_buf + 1, pass_row_size,
png_get_interlaced_row(progressive_buf, pass_row_size,
bits_per_pixel, pass,
ptr1, avctx->width);
crow_buf[0] = PNG_FILTER_VALUE_NONE;
png_write_row(s, crow_buf, pass_row_size + 1);
ptr, avctx->width);
crow = png_choose_filter(s, crow_buf, progressive_buf, top, pass_row_size, bits_per_pixel>>3);
png_write_row(s, crow, pass_row_size + 1);
top = progressive_buf;
}
}
}
}
} else {
top = NULL;
for(y = 0; y < avctx->height; y++) {
ptr = p->data[0] + y * p->linesize[0];
if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
convert_from_rgb32(crow_buf + 1, ptr, avctx->width);
else
memcpy(crow_buf + 1, ptr, row_size);
crow_buf[0] = PNG_FILTER_VALUE_NONE;
png_write_row(s, crow_buf, row_size + 1);
if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) {
FFSWAP(uint8_t*, rgba_buf, top_buf);
convert_from_rgb32(rgba_buf, ptr, avctx->width);
ptr = rgba_buf;
}
crow = png_choose_filter(s, crow_buf, ptr, top, row_size, bits_per_pixel>>3);
png_write_row(s, crow, row_size + 1);
top = ptr;
}
}
/* compress last bytes */
@ -304,8 +411,10 @@ static int encode_frame(AVCodecContext *avctx, unsigned char *buf, int buf_size,
ret = s->bytestream - s->bytestream_start;
the_end:
av_free(crow_buf);
av_free(tmp_buf);
av_free(crow_base);
av_free(progressive_buf);
av_free(rgba_buf);
av_free(top_buf);
deflateEnd(&s->zstream);
return ret;
fail:
@ -318,6 +427,11 @@ static int png_enc_init(AVCodecContext *avctx){
avcodec_get_frame_defaults((AVFrame*)&s->picture);
avctx->coded_frame= (AVFrame*)&s->picture;
dsputil_init(&s->dsp, avctx);
s->filter_type = av_clip(avctx->prediction_method, PNG_FILTER_VALUE_NONE, PNG_FILTER_VALUE_MIXED);
if(avctx->pix_fmt == PIX_FMT_MONOBLACK)
s->filter_type = PNG_FILTER_VALUE_NONE;
return 0;
}