Pillow/src/libImaging/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 "ZipCodecs.h"

int
ImagingZipEncode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
{
    ZIPSTATE* context = (ZIPSTATE*) state->context;
    int err;
    int compress_level, compress_type;
    UINT8* ptr;
    int i, bpp, s, sum;
    ImagingSectionCookie cookie;

    if (!state->state) {

        /* Initialization */

        /* Valid modes are ZIP_PNG, ZIP_PNG_PALETTE, and ZIP_TIFF */

        /* overflow check for malloc */
        if (state->bytes > INT_MAX - 1) {
            state->errcode = IMAGING_CODEC_MEMORY;
            return -1;
        }

        /* Expand standard buffer to make room for the filter selector,
           and allocate filter buffers */
        free(state->buffer);
        /* malloc check ok, overflow checked above */
        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;
        }

        /* Initialise 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;

        compress_level = (context->optimize) ? Z_BEST_COMPRESSION
                                             : context->compress_level;

        if (context->compress_type == -1) {
            compress_type = (context->mode == ZIP_PNG) ? Z_FILTERED
                                                       : Z_DEFAULT_STRATEGY;
        } else {
            compress_type = context->compress_type;
        }

        err = deflateInit2(&context->z_stream,
                           /* compression level */
                           compress_level,
                           /* compression method */
                           Z_DEFLATED,
                           /* compression memory resources */
                           15, 9,
                           /* compression strategy (image data are filtered)*/
                           compress_type);
        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;
}

/* -------------------------------------------------------------------- */
/* Cleanup                                                              */
/* -------------------------------------------------------------------- */

int
ImagingZipEncodeCleanup(ImagingCodecState state) {
    ZIPSTATE* context = (ZIPSTATE*) state->context;

    if (context->dictionary) {
        free (context->dictionary);
        context->dictionary = NULL;
    }

    return -1;
}



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

#endif