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/*
* The Python Imaging Library.
* $Id: ZipEncode.c 2134 2004-10-06 08:55:20Z fredrik $
*
* coder for ZIP (deflated) image data
*
* History:
* 96-12-29 fl created
* 96-12-30 fl adaptive filter selection, encoder tuning
*
* Copyright (c) Fredrik Lundh 1996.
* Copyright (c) Secret Labs AB 1997.
*
* See the README file for information on usage and redistribution.
*/
#include "Imaging.h"
#ifdef HAVE_LIBZ
#include "Zip.h"
int
ImagingZipEncode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
{
ZIPSTATE* context = (ZIPSTATE*) state->context;
int err;
UINT8* ptr;
int i, bpp, s, sum;
if (!state->state) {
/* Initialization */
/* Valid modes are ZIP_PNG, ZIP_PNG_PALETTE, and ZIP_TIFF */
/* Expand standard buffer to make room for the filter selector,
and allocate filter buffers */
free(state->buffer);
state->buffer = (UINT8*) malloc(state->bytes+1);
context->previous = (UINT8*) malloc(state->bytes+1);
context->prior = (UINT8*) malloc(state->bytes+1);
context->up = (UINT8*) malloc(state->bytes+1);
context->average = (UINT8*) malloc(state->bytes+1);
context->paeth = (UINT8*) malloc(state->bytes+1);
if (!state->buffer || !context->previous || !context->prior ||
!context->up || !context->average || !context->paeth) {
free(context->paeth);
free(context->average);
free(context->up);
free(context->prior);
free(context->previous);
state->errcode = IMAGING_CODEC_MEMORY;
return -1;
}
/* Initalise filter buffers */
state->buffer[0] = 0;
context->prior[0] = 1;
context->up[0] = 2;
context->average[0] = 3;
context->paeth[0] = 4;
/* Initialise previous buffer to black */
memset(context->previous, 0, state->bytes+1);
/* Setup compression context */
context->z_stream.zalloc = (alloc_func)0;
context->z_stream.zfree = (free_func)0;
context->z_stream.opaque = (voidpf)0;
err = deflateInit2(&context->z_stream,
/* compression level */
(context->optimize) ? Z_BEST_COMPRESSION
: Z_DEFAULT_COMPRESSION,
/* compression method */
Z_DEFLATED,
/* compression memory resources */
15, 9,
/* compression strategy (image data are filtered)*/
(context->mode == ZIP_PNG) ? Z_FILTERED
: Z_DEFAULT_STRATEGY);
if (err < 0) {
state->errcode = IMAGING_CODEC_CONFIG;
return -1;
}
if (context->dictionary && context->dictionary_size > 0) {
err = deflateSetDictionary(&context->z_stream, (unsigned char *)context->dictionary,
context->dictionary_size);
if (err < 0) {
state->errcode = IMAGING_CODEC_CONFIG;
return -1;
}
}
/* Ready to decode */
state->state = 1;
}
/* Setup the destination buffer */
context->z_stream.next_out = buf;
context->z_stream.avail_out = bytes;
for (;;) {
switch (state->state) {
case 1:
/* Compress image data */
while (context->z_stream.avail_out > 0) {
if (state->y >= state->ysize) {
/* End of image; now flush compressor buffers */
state->state = 2;
break;
}
/* Stuff image data into the compressor */
state->shuffle(state->buffer+1,
(UINT8*) im->image[state->y + state->yoff] +
state->xoff * im->pixelsize,
state->xsize);
state->y++;
context->output = state->buffer;
if (context->mode == ZIP_PNG) {
/* Filter the image data. For each line, select
the filter that gives the least total distance
from zero for the filtered data (taken from
LIBPNG) */
bpp = (state->bits + 7) / 8;
/* 0. No filter */
for (i = 1, sum = 0; i <= state->bytes; i++) {
UINT8 v = state->buffer[i];
sum += (v < 128) ? v : 256 - v;
}
/* 2. Up. We'll test this first to save time when
an image line is identical to the one above. */
if (sum > 0) {
for (i = 1, s = 0; i <= state->bytes; i++) {
UINT8 v = state->buffer[i] - context->previous[i];
context->up[i] = v;
s += (v < 128) ? v : 256 - v;
}
if (s < sum) {
context->output = context->up;
sum = s; /* 0 if line was duplicated */
}
}
/* 1. Prior */
if (sum > 0) {
for (i = 1, s = 0; i <= bpp; i++) {
UINT8 v = state->buffer[i];
context->prior[i] = v;
s += (v < 128) ? v : 256 - v;
}
for (; i <= state->bytes; i++) {
UINT8 v = state->buffer[i] - state->buffer[i-bpp];
context->prior[i] = v;
s += (v < 128) ? v : 256 - v;
}
if (s < sum) {
context->output = context->prior;
sum = s; /* 0 if line is solid */
}
}
/* 3. Average (not very common in real-life images,
so its only used with the optimize option) */
if (context->optimize && sum > 0) {
for (i = 1, s = 0; i <= bpp; i++) {
UINT8 v = state->buffer[i] - context->previous[i]/2;
context->average[i] = v;
s += (v < 128) ? v : 256 - v;
}
for (; i <= state->bytes; i++) {
UINT8 v = state->buffer[i] -
(state->buffer[i-bpp] + context->previous[i])/2;
context->average[i] = v;
s += (v < 128) ? v : 256 - v;
}
if (s < sum) {
context->output = context->average;
sum = s;
}
}
/* 4. Paeth */
if (sum > 0) {
for (i = 1, s = 0; i <= bpp; i++) {
UINT8 v = state->buffer[i] - context->previous[i];
context->paeth[i] = v;
s += (v < 128) ? v : 256 - v;
}
for (; i <= state->bytes; i++) {
UINT8 v;
int a, b, c;
int pa, pb, pc;
/* fetch pixels */
a = state->buffer[i-bpp];
b = context->previous[i];
c = context->previous[i-bpp];
/* distances to surrounding pixels */
pa = abs(b - c);
pb = abs(a - c);
pc = abs(a + b - 2*c);
/* pick predictor with the shortest distance */
v = state->buffer[i] -
((pa <= pb && pa <= pc) ? a :
(pb <= pc) ? b : c);
context->paeth[i] = v;
s += (v < 128) ? v : 256 - v;
}
if (s < sum) {
context->output = context->paeth;
sum = s;
}
}
}
/* Compress this line */
context->z_stream.next_in = context->output;
context->z_stream.avail_in = state->bytes+1;
/* err = deflate(&context->z_stream, Z_NO_FLUSH); */
/* FIXME: temporary workaround for problem with recent
versions of zlib -- 990709/fl */
err = deflate(&context->z_stream, Z_SYNC_FLUSH);
if (err < 0) {
/* Something went wrong inside the compression library */
if (err == Z_DATA_ERROR)
state->errcode = IMAGING_CODEC_BROKEN;
else if (err == Z_MEM_ERROR)
state->errcode = IMAGING_CODEC_MEMORY;
else
state->errcode = IMAGING_CODEC_CONFIG;
free(context->paeth);
free(context->average);
free(context->up);
free(context->prior);
free(context->previous);
deflateEnd(&context->z_stream);
return -1;
}
/* Swap buffer pointers */
ptr = state->buffer;
state->buffer = context->previous;
context->previous = ptr;
}
if (context->z_stream.avail_out == 0)
break; /* Buffer full */
case 2:
/* End of image data; flush compressor buffers */
while (context->z_stream.avail_out > 0) {
err = deflate(&context->z_stream, Z_FINISH);
if (err == Z_STREAM_END) {
free(context->paeth);
free(context->average);
free(context->up);
free(context->prior);
free(context->previous);
deflateEnd(&context->z_stream);
state->errcode = IMAGING_CODEC_END;
break;
}
if (context->z_stream.avail_out == 0)
break; /* Buffer full */
}
}
return bytes - context->z_stream.avail_out;
}
/* Should never ever arrive here... */
state->errcode = IMAGING_CODEC_CONFIG;
return -1;
}
#endif
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