/*
 * Orginal copyright from libpng example code
 *
 * Copyright 2002-2011 Guillaume Cottenceau and contributors.
 *
 * This software may be freely redistributed under the terms
 * of the X11 license.
 *
 */


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

#include "imagecon.h"

png_bytep* 
png_read(char* file_name)
{
  png_structp png_ptr; 
  png_byte color_type;
  png_byte bit_depth; 
  png_infop info_ptr;
  int number_of_passes, rowbytes;
  unsigned char header[8];    // 8 is the maximum size that can be checked
  
  /* open file and test for it being a png */
  FILE *fp = fopen(file_name, "rb");
  if (!fp)
    abort_("Failed to open %s", file_name);
  fread(header, 1, 8, fp);
  if (png_sig_cmp(header, 0, 8))
    abort_("File %s is not recognized as a PNG file", file_name);

  png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);  

  if (!png_ptr)
    abort_("png_create_read_struct failed");
  
  info_ptr = png_create_info_struct(png_ptr);
  if (!info_ptr)
    abort_("png_create_info_struct failed");
  
  if (setjmp(png_jmpbuf(png_ptr)))
    abort_("Error during init_io");
  
  png_init_io(png_ptr, fp);
  png_set_sig_bytes(png_ptr, 8);
  
  png_read_info(png_ptr, info_ptr);
  
  config.width = png_get_image_width(png_ptr, info_ptr);
  config.height = png_get_image_height(png_ptr, info_ptr);
  color_type = png_get_color_type(png_ptr, info_ptr);
  bit_depth = png_get_bit_depth(png_ptr, info_ptr);

  if (config.verbose) {
    printf("width = %d\n", config.width);
    printf("height = %d\n", config.height);
    printf("color_type = %d (palette = %s)\n", color_type, color_type == PNG_COLOR_TYPE_PALETTE ? "yes" : "no");
    printf("bit_depth = %d\n", bit_depth);
    printf("number_of_passes = %d\n", number_of_passes);
  }
  
  if (color_type == PNG_COLOR_TYPE_PALETTE)
    png_set_palette_to_rgb(png_ptr);

  if (color_type == PNG_COLOR_TYPE_GRAY && bit_depth < 8) 
    png_set_expand_gray_1_2_4_to_8(png_ptr);

  if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) 
    png_set_tRNS_to_alpha(png_ptr);

  if (color_type == PNG_COLOR_TYPE_RGB ||
      color_type == PNG_COLOR_TYPE_GRAY || 
      color_type == PNG_COLOR_TYPE_PALETTE)
    png_set_add_alpha(png_ptr, 0xFF, PNG_FILLER_AFTER);
  
  if (bit_depth == 16)
    png_set_strip_16(png_ptr);  

  number_of_passes = png_set_interlace_handling(png_ptr);

  png_read_update_info(png_ptr, info_ptr);  
  config.width = png_get_image_width(png_ptr, info_ptr);
  config.height = png_get_image_height(png_ptr, info_ptr);
  color_type = png_get_color_type(png_ptr, info_ptr);
  bit_depth = png_get_bit_depth(png_ptr, info_ptr);

  if (setjmp(png_jmpbuf(png_ptr)))
    abort_("Error during read_image");
  
  png_bytep* rowPointers = (png_bytep*) malloc(sizeof(png_bytep) * config.height);
  
  if (bit_depth == 16)
    rowbytes = config.width*8;
  else
    rowbytes = config.width*4;
  
  for (int y=0; y<config.height; y++)
    rowPointers[y] = (png_byte*) malloc(rowbytes);
  
  png_read_image(png_ptr, rowPointers);
  
  fclose(fp);

  if (config.verbose) {
    printf("width = %d\n", config.width);
    printf("height = %d\n", config.height);
    printf("color_type = %d (palette = %s)\n", color_type, color_type == PNG_COLOR_TYPE_PALETTE ? "yes" : "no");
    printf("bit_depth = %d\n", bit_depth);
    printf("number_of_passes = %d\n", number_of_passes);
  }

  return rowPointers;
}