img-png.c

/*
 * A simple libpng example program
 * http://zarb.org/~gc/html/libpng.html
 *
 * Modified by Yoshimasa Niwa to make it much simpler
 * and support all defined color_type.
 *
 * To build, use the next instruction on OS X.
 * $ brew install libpng
 * $ clang -lz -lpng15 libpng_test.c
 *
 * Copyright 2002-2010 Guillaume Cottenceau.
 *
 * This software may be freely redistributed under the terms
 * of the X11 license.
 *
 */

 #include <stdlib.h>
 #include <stdio.h>
 #include <png.h>
 #include "img-png.h"

 // Adapted libpng demo to write to our image_t struct.
image_t* read_png_file(char *filename) {
   int width, height;
   png_byte color_type;
   png_byte bit_depth;
   png_bytep *row_pointers;

   FILE *fp = fopen(filename, "rb");
 
   png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
   if(!png) abort();
 
   png_infop info = png_create_info_struct(png);
   if(!info) abort();
 
   if(setjmp(png_jmpbuf(png))) abort();
 
   png_init_io(png, fp);
 
   png_read_info(png, info);
 
   width      = png_get_image_width(png, info);
   height     = png_get_image_height(png, info);
   color_type = png_get_color_type(png, info);
   bit_depth  = png_get_bit_depth(png, info);
 
   // Read any color_type into 8bit depth, RGBA format.
   // See http://www.libpng.org/pub/png/libpng-manual.txt
 
   if(bit_depth == 16)
     png_set_strip_16(png);
 
   if(color_type == PNG_COLOR_TYPE_PALETTE)
     png_set_palette_to_rgb(png);
 
   // PNG_COLOR_TYPE_GRAY_ALPHA is always 8 or 16bit depth.
   if(color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8)
     png_set_expand_gray_1_2_4_to_8(png);
 
   if(png_get_valid(png, info, PNG_INFO_tRNS))
     png_set_tRNS_to_alpha(png);
 
   // These color_type don't have an alpha channel then fill it with 0xff.
   if(color_type == PNG_COLOR_TYPE_RGB ||
      color_type == PNG_COLOR_TYPE_GRAY ||
      color_type == PNG_COLOR_TYPE_PALETTE)
     png_set_filler(png, 0xFF, PNG_FILLER_AFTER);
 
   if(color_type == PNG_COLOR_TYPE_GRAY ||
      color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
     png_set_gray_to_rgb(png);
 
   png_read_update_info(png, info);
 
   row_pointers = (png_bytep*)malloc(sizeof(png_bytep) * height);
   for(int y = 0; y < height; y++) {
     row_pointers[y] = (png_byte*)malloc(png_get_rowbytes(png,info));
   }
 
   png_read_image(png, row_pointers);
 
   image_t* image_array = malloc(sizeof(image_t));
   image_array->data = malloc(width * height * sizeof(int));
   image_array->width = width;
   image_array->height = height;

   for(int y = 0; y < height; y++) {
    png_bytep row = row_pointers[y];
    for(int x = 0; x < width; x++) {
      png_bytep px = &(row[x * 4]);
      int hexval = ((px[0] << 16) & 0xFF0000) | ((px[1] << 8) & 0x00FF00) | ((px[2]) & 0x0000FF);
      
      // Save to the thing. todo: take image background param.
      image_array->data[y * width + x] = hexval;
      
      //printf("%4d, %4d = RGBA(%x, %x, %x, %x) #%x\n", x, y, px[0], px[1], px[2], px[3], hexval);
    }
  }

  // Free the roes, 
  for(int y = 0; y < height; y++) {
    free(row_pointers[y]);
  }

  free(row_pointers);

   fclose(fp);

   return image_array;
 }
 
//  void write_png_file(char *filename) {
//    int y;
 
//    FILE *fp = fopen(filename, "wb");
//    if(!fp) abort();
 
//    png_structp png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
//    if (!png) abort();
 
//    png_infop info = png_create_info_struct(png);
//    if (!info) abort();
 
//    if (setjmp(png_jmpbuf(png))) abort();
 
//    png_init_io(png, fp);
 
//    // Output is 8bit depth, RGBA format.
//    png_set_IHDR(
//      png,
//      info,
//      width, height,
//      8,
//      PNG_COLOR_TYPE_RGBA,
//      PNG_INTERLACE_NONE,
//      PNG_COMPRESSION_TYPE_DEFAULT,
//      PNG_FILTER_TYPE_DEFAULT
//    );
//    png_write_info(png, info);
 
//    // To remove the alpha channel for PNG_COLOR_TYPE_RGB format,
//    // Use png_set_filler().
//    //png_set_filler(png, 0, PNG_FILLER_AFTER);
 
//    png_write_image(png, row_pointers);
//    png_write_end(png, NULL);
 
//    for(int y = 0; y < height; y++) {
//      free(row_pointers[y]);
//    }
//    free(row_pointers);
 
//    fclose(fp);
//  }
 
//  int main(int argc, char *argv[]) {
//   // if(argc != 3) abort();
 
//    read_png_file("./test.png");
//   // process_png_file();
//    //write_png_file(argv[2]);
 
//    return 0;
//  }