rwpng.c

/*---------------------------------------------------------------------------

   pngquant:  RGBA -> RGBA-palette quantization program             rwpng.c

  ---------------------------------------------------------------------------

      Copyright (c) 1998-2000 Greg Roelofs.  All rights reserved.

      This software is provided "as is," without warranty of any kind,
      express or implied.  In no event shall the author or contributors
      be held liable for any damages arising in any way from the use of
      this software.

      Permission is granted to anyone to use this software for any purpose,
      including commercial applications, and to alter it and redistribute
      it freely, subject to the following restrictions:

      1. Redistributions of source code must retain the above copyright
         notice, disclaimer, and this list of conditions.
      2. Redistributions in binary form must reproduce the above copyright
         notice, disclaimer, and this list of conditions in the documenta-
         tion and/or other materials provided with the distribution.
      3. All advertising materials mentioning features or use of this
         software must display the following acknowledgment:

            This product includes software developed by Greg Roelofs
            and contributors for the book, "PNG: The Definitive Guide,"
            published by O'Reilly and Associates.

  ---------------------------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>

#include "png.h"
#include "zlib.h"
#include "rwpng.h"

static void rwpng_error_handler(png_structp png_ptr, png_const_charp msg);


void rwpng_version_info(FILE *fp)
{
    fprintf(fp, "   Compiled with libpng %s; using libpng %s.\n",
      PNG_LIBPNG_VER_STRING, png_get_header_ver(NULL));
    fprintf(fp, "   Compiled with zlib %s; using zlib %s.\n",
      ZLIB_VERSION, zlib_version);
}


struct rwpng_read_data {
    FILE *fp;
    png_size_t bytes_read;
};

static void user_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
{
    struct rwpng_read_data *read_data = (struct rwpng_read_data *)png_get_io_ptr(png_ptr);

    png_size_t read = fread(data, 1, length, read_data->fp);
    if (!read) png_error(png_ptr, "Read error");
    read_data->bytes_read += read;
}


/*
   retval:
     0 = success
    21 = bad sig
    22 = bad IHDR
    24 = insufficient memory
    25 = libpng error (via longjmp())
    26 = wrong PNG color type (no alpha channel)
 */

pngquant_error rwpng_read_image(FILE *infile, read_info *mainprog_ptr)
{
    png_structp  png_ptr = NULL;
    png_infop    info_ptr = NULL;
    png_uint_32  i;
    png_size_t   rowbytes;
    int          color_type, bit_depth;

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr,
      rwpng_error_handler, NULL);
    if (!png_ptr) {
        return PNG_OUT_OF_MEMORY_ERROR;   /* out of memory */
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_read_struct(&png_ptr, NULL, NULL);
        return PNG_OUT_OF_MEMORY_ERROR;   /* out of memory */
    }

    /* setjmp() must be called in every function that calls a non-trivial
     * libpng function */

    if (setjmp(mainprog_ptr->jmpbuf)) {
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        return LIBPNG_FATAL_ERROR;   /* fatal libpng error (via longjmp()) */
    }

    struct rwpng_read_data read_data = {infile, 0};
    png_set_read_fn(png_ptr, &read_data, user_read_data);

    png_read_info(png_ptr, info_ptr);  /* read all PNG info up to image data */


    /* alternatively, could make separate calls to png_get_image_width(),
     * etc., but want bit_depth and color_type for later [don't care about
     * compression_type and filter_type => NULLs] */

    png_get_IHDR(png_ptr, info_ptr, &mainprog_ptr->width, &mainprog_ptr->height,
      &bit_depth, &color_type, &mainprog_ptr->interlaced, NULL, NULL);


    /* expand palette images to RGB, low-bit-depth grayscale images to 8 bits,
     * transparency chunks to full alpha channel; strip 16-bit-per-sample
     * images to 8 bits per sample; and convert grayscale to RGB[A] */

    /* GRR TO DO:  preserve all safe-to-copy ancillary PNG chunks */

    if (!(color_type & PNG_COLOR_MASK_ALPHA)) {
#ifdef PNG_READ_FILLER_SUPPORTED
        /* GRP:  expand palette to RGB, and grayscale or RGB to GA or RGBA */
        if (color_type == PNG_COLOR_TYPE_PALETTE)
            png_set_expand(png_ptr);
        png_set_filler(png_ptr, 65535L, PNG_FILLER_AFTER);
#else
        fprintf(stderr, "pngquant readpng:  image is neither RGBA nor GA\n");
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        mainprog_ptr->retval = 26;
        return mainprog_ptr->retval;
#endif
    }
/*
    if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
        png_set_expand(png_ptr);
    if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS))
        png_set_expand(png_ptr);
 */
    if (bit_depth == 16)
        png_set_strip_16(png_ptr);

    if (color_type == PNG_COLOR_TYPE_GRAY ||
        color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(png_ptr);


    /* get and save the gamma info (if any) for writing */

    double gamma;
    mainprog_ptr->gamma = png_get_gAMA(png_ptr, info_ptr, &gamma) ? gamma : 0.45455f;

    png_set_interlace_handling(png_ptr);

    /* all transformations have been registered; now update info_ptr data,
     * get rowbytes and channels, and allocate image memory */

    png_read_update_info(png_ptr, info_ptr);

    mainprog_ptr->rowbytes = rowbytes = png_get_rowbytes(png_ptr, info_ptr);
    //mainprog_ptr->channels = (int)png_get_channels(png_ptr, info_ptr);

    if ((mainprog_ptr->rgba_data = malloc(rowbytes*mainprog_ptr->height)) == NULL) {
        fprintf(stderr, "pngquant readpng:  unable to allocate image data\n");
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        return PNG_OUT_OF_MEMORY_ERROR;
    }
    if ((mainprog_ptr->row_pointers = (png_bytepp)malloc(mainprog_ptr->height*sizeof(png_bytep))) == NULL) {
        fprintf(stderr, "pngquant readpng:  unable to allocate row pointers\n");
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        free(mainprog_ptr->rgba_data);
        mainprog_ptr->rgba_data = NULL;
        return PNG_OUT_OF_MEMORY_ERROR;
    }

    /* set the individual row_pointers to point at the correct offsets */

    for (i = 0;  i < mainprog_ptr->height;  ++i)
        mainprog_ptr->row_pointers[i] = mainprog_ptr->rgba_data + i*rowbytes;


    /* now we can go ahead and just read the whole image */

    png_read_image(png_ptr, (png_bytepp)mainprog_ptr->row_pointers);


    /* and we're done!  (png_read_end() can be omitted if no processing of
     * post-IDAT text/time/etc. is desired) */

    png_read_end(png_ptr, NULL);

    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);

    mainprog_ptr->file_size = read_data.bytes_read;

    return SUCCESS;
}





/*
   retval:
     0 = success
    34 = insufficient memory
    35 = libpng error (via longjmp())
 */

pngquant_error rwpng_write_image(FILE *outfile, write_info *mainprog_ptr)
{
    png_structp png_ptr;       /* note:  temporary variables! */
    png_infop info_ptr;


    /* could also replace libpng warning-handler (final NULL), but no need: */

    png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, mainprog_ptr,
      rwpng_error_handler, NULL);
    if (!png_ptr) {
        return INIT_OUT_OF_MEMORY_ERROR;   /* out of memory */
    }

    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_write_struct(&png_ptr, NULL);
        return INIT_OUT_OF_MEMORY_ERROR;   /* out of memory */
    }


    /* setjmp() must be called in every function that calls a PNG-writing
     * libpng function, unless an alternate error handler was installed--
     * but compatible error handlers must either use longjmp() themselves
     * (as in this program) or exit immediately, so here we go: */

    if (setjmp(mainprog_ptr->jmpbuf)) {
        png_destroy_write_struct(&png_ptr, &info_ptr);
        return LIBPNG_INIT_ERROR;   /* libpng error (via longjmp()) */
    }


    /* make sure outfile is (re)opened in BINARY mode */

    png_init_io(png_ptr, outfile);

    png_set_compression_level(png_ptr, Z_BEST_COMPRESSION);

    // Palette images generally don't gain anything from filtering
    png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_FILTER_VALUE_NONE);

    /* set the image parameters appropriately */
    int sample_depth;
    if (mainprog_ptr->num_palette <= 2)
        sample_depth = 1;
    else if (mainprog_ptr->num_palette <= 4)
        sample_depth = 2;
    else if (mainprog_ptr->num_palette <= 16)
        sample_depth = 4;
    else
        sample_depth = 8;

    png_set_IHDR(png_ptr, info_ptr, mainprog_ptr->width, mainprog_ptr->height,
      sample_depth, PNG_COLOR_TYPE_PALETTE,
      mainprog_ptr->interlaced, PNG_COMPRESSION_TYPE_DEFAULT,
      PNG_FILTER_TYPE_BASE);

    /* GRR WARNING:  cast of rwpng_colorp to png_colorp could fail in future
     * major revisions of libpng (but png_ptr/info_ptr will fail, regardless) */
    png_set_PLTE(png_ptr, info_ptr, &mainprog_ptr->palette[0], mainprog_ptr->num_palette);

    if (mainprog_ptr->num_trans > 0)
        png_set_tRNS(png_ptr, info_ptr, mainprog_ptr->trans, mainprog_ptr->num_trans, NULL);

    if (mainprog_ptr->gamma > 0.0)
        png_set_gAMA(png_ptr, info_ptr, mainprog_ptr->gamma);


    /* write all chunks up to (but not including) first IDAT */
    png_write_info(png_ptr, info_ptr);


    /* if we wanted to write any more text info *after* the image data, we
     * would set up text struct(s) here and call png_set_text() again, with
     * just the new data; png_set_tIME() could also go here, but it would
     * have no effect since we already called it above (only one tIME chunk
     * allowed) */


    /* set up the transformations:  for now, just pack low-bit-depth pixels
     * into bytes (one, two or four pixels per byte) */

    png_set_packing(png_ptr);


    /* and now we just write the whole image; libpng takes care of interlacing
     * for us */

    png_write_image(png_ptr, mainprog_ptr->row_pointers);


    /* since that's it, we also close out the end of the PNG file now--if we
     * had any text or time info to write after the IDATs, second argument
     * would be info_ptr, but we optimize slightly by sending NULL pointer: */

    png_write_end(png_ptr, NULL);

    png_destroy_write_struct(&png_ptr, &info_ptr);

    return SUCCESS;
}


static void rwpng_error_handler(png_structp png_ptr, png_const_charp msg)
{
    read_or_write_info  *mainprog_ptr;

    /* This function, aside from the extra step of retrieving the "error
     * pointer" (below) and the fact that it exists within the application
     * rather than within libpng, is essentially identical to libpng's
     * default error handler.  The second point is critical:  since both
     * setjmp() and longjmp() are called from the same code, they are
     * guaranteed to have compatible notions of how big a jmp_buf is,
     * regardless of whether _BSD_SOURCE or anything else has (or has not)
     * been defined. */

    fprintf(stderr, "  error: %s\n", msg);
    fflush(stderr);

    mainprog_ptr = png_get_error_ptr(png_ptr);
    if (mainprog_ptr == NULL) abort();

    longjmp(mainprog_ptr->jmpbuf, 1);
}