ZipEncode.c

/*
 * The Python Imaging Library.
 * $Id$
 *
 * 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;
    ImagingSectionCookie cookie;

    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;
	context->z_stream.next_in = 0;
	context->z_stream.avail_in = 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;
    if (context->z_stream.next_in && context->z_stream.avail_in > 0) {
	/* We have some data from previous round, deflate it first */
	err = deflate(&context->z_stream, Z_NO_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;
	}
    }

    ImagingSectionEnter(&cookie);
    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);

		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);
		    ImagingSectionLeave(&cookie);
		    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 */

	    }

	}
	ImagingSectionLeave(&cookie);
	return bytes - context->z_stream.avail_out;

    }

    /* Should never ever arrive here... */
    state->errcode = IMAGING_CODEC_CONFIG;
    ImagingSectionLeave(&cookie);
    return -1;
}

const char*
ImagingZipVersion(void)
{
    return ZLIB_VERSION;
}

#endif