slim/png.c

/****************************************************************************
    png.c - read and write png images using libpng routines.
    Distributed with Xplanet.
    Copyright (C) 2002 Hari Nair <hari@alumni.caltech.edu>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
****************************************************************************/

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

#include <png.h>
#include "const.h"

int
read_png(const char *filename, int *width, int *height, unsigned char **rgb, 
     unsigned char **alpha)
{
    int ret = 0;

    png_structp png_ptr;
    png_infop info_ptr;
    png_bytepp row_pointers;

    unsigned char *ptr = NULL;
    png_uint_32 w, h;
    int bit_depth, color_type, interlace_type;
    int i;

    FILE *infile = fopen(filename, "rb");
    if (infile == NULL) {
        fprintf(stderr, "Can not fopen file: %s\n",filename);
        return ret;
    }

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, 
                                     (png_voidp) NULL, 
                                     (png_error_ptr) NULL, 
                                     (png_error_ptr) NULL);
    if (!png_ptr)
        goto file_close;
  
    info_ptr = png_create_info_struct(png_ptr);
    if (!info_ptr) {
        png_destroy_read_struct(&png_ptr, (png_infopp) NULL, 
                                (png_infopp) NULL);
    }
  
    if (setjmp(png_ptr->jmpbuf))
        goto png_destroy;
  
    png_init_io(png_ptr, infile);
    png_read_info(png_ptr, info_ptr);

    png_get_IHDR(png_ptr, info_ptr, &w, &h, &bit_depth, &color_type,
                 &interlace_type, (int *) NULL, (int *) NULL);

    /* Prevent against integer overflow */
    if(w >= MAX_DIMENSION || h >= MAX_DIMENSION) {
        fprintf(stderr, "Unreasonable dimension found in file: %s\n",filename);
        goto png_destroy;
    }

    *width = (int) w;
    *height = (int) h;
    
    if (color_type == PNG_COLOR_TYPE_RGB_ALPHA
        || color_type == PNG_COLOR_TYPE_GRAY_ALPHA) {
        alpha[0] = malloc(*width * *height);
        if (alpha[0] == NULL)
        {
            fprintf(stderr, "Can't allocate memory for alpha channel in PNG file.\n");
            goto png_destroy;
        }
    }

    /* Change a paletted/grayscale image to RGB */
    if (color_type == PNG_COLOR_TYPE_PALETTE && bit_depth <= 8) 
        png_set_expand(png_ptr);

    /* Change a grayscale image to RGB */
    if (color_type == PNG_COLOR_TYPE_GRAY 
        || color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
        png_set_gray_to_rgb(png_ptr);

    /* If the PNG file has 16 bits per channel, strip them down to 8 */
    if (bit_depth == 16)
        png_set_strip_16(png_ptr);

    /* use 1 byte per pixel */
    png_set_packing(png_ptr);

    row_pointers = malloc(*height * sizeof(png_bytep));
    if (row_pointers == NULL) {
        fprintf(stderr, "Can't allocate memory for PNG file.\n");
        goto png_destroy;
    }

    for (i = 0; i < *height; i++) {
        row_pointers[i] = malloc(4 * *width);
        if (row_pointers == NULL) {
            fprintf(stderr, "Can't allocate memory for PNG line.\n");
            goto rows_free;
        }
    }

    png_read_image(png_ptr, row_pointers);

    rgb[0] = malloc(3 * *width * *height);
    if (rgb[0] == NULL) {
        fprintf(stderr, "Can't allocate memory for PNG file.\n");
        goto rows_free;
    }

    if (alpha[0] == NULL)
    {
        ptr = rgb[0];
        for (i = 0; i < *height; i++) {
            memcpy(ptr, row_pointers[i], 3 * *width);
            ptr += 3 * *width;
        }
    } else {
        int j;
        ptr = rgb[0];
        for (i = 0; i < *height; i++) {
            int ipos = 0;
            for (j = 0; j < *width; j++) {
                *ptr++ = row_pointers[i][ipos++];
                *ptr++ = row_pointers[i][ipos++];
                *ptr++ = row_pointers[i][ipos++];
                alpha[0][i * *width + j] = row_pointers[i][ipos++];
            }
        }
    }

    ret = 1; /* data reading is OK */

rows_free:
    for (i = 0; i < *height; i++) {
        if (row_pointers[i] != NULL ) {
            free(row_pointers[i]);
        }
    }

    free(row_pointers);

png_destroy:
    png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp) NULL);

file_close:
    fclose(infile);
    return(ret);
}