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

#include "pngLoad.h" 


int pngLoad(char *file, unsigned long **pwidth, 
	unsigned long **pheight, char **image_data_ptr)
{

   FILE         *infile;         /* PNG file pointer */
   png_structp   png_ptr;        /* internally used by libpng */
   png_infop     info_ptr;       /* user requested transforms */

   char         *image_data;      /* raw png image data */
   char         sig[8];           /* PNG signature array */
   /*char         **row_pointers;   */

   int           bit_depth;
   int           color_type;

   unsigned long width;            /* PNG image width in pixels */
   unsigned long height;           /* PNG image height in pixels */
   unsigned int rowbytes;         /* raw bytes at row n in image */

   image_data = NULL;
   int i;
   png_bytepp row_pointers = NULL;

   /* Open the file. */
   infile = fopen(file, "rb");
   if (!infile) {
      return 0;
   }


   /*
    * 		13.3 readpng_init()
    */
	
   /* Check for the 8-byte signature */
   fread(sig, 1, 8, infile);

   if (!png_check_sig((unsigned char *) sig, 8)) {
      fclose(infile);
      return 0;
   }
 
   /* 
    * Set up the PNG structs 
    */
   png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
   if (!png_ptr) {
      fclose(infile);
      return 4;    /* out of memory */
   }
 
   info_ptr = png_create_info_struct(png_ptr);
   if (!info_ptr) {
      png_destroy_read_struct(&png_ptr, (png_infopp) NULL, (png_infopp) NULL);
      fclose(infile);
      return 4;    /* out of memory */
   }
   
  
  /*
   * block to handle libpng errors, 
   * then check whether the PNG file had a bKGD chunk
   */
   if (setjmp(png_jmpbuf(png_ptr))) {
      png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
      fclose(infile);
      return 0;
   }

  /* 
   * takes our file stream pointer (infile) and 
   * stores it in the png_ptr struct for later use.
   */
   /* png_ptr->io_ptr = (png_voidp)infile;*/
   png_init_io(png_ptr, infile);
   
  /*
   * lets libpng know that we already checked the 8 
   * signature bytes, so it should not expect to find 
   * them at the current file pointer location
   */
   png_set_sig_bytes(png_ptr, 8);
   
   /* Read the image info.*/

  /*
   * reads and processes not only the PNG file's IHDR chunk 
   * but also any other chunks up to the first IDAT 
   * (i.e., everything before the image data).
   */

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

   png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, 
	&color_type, NULL, NULL, NULL);

   *pwidth = width;
   *pheight = height;
   
   /* Set up some transforms. */
   if (color_type & PNG_COLOR_MASK_ALPHA) {
      png_set_strip_alpha(png_ptr);
   }
   if (bit_depth > 8) {
      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);
   }
   if (color_type == PNG_COLOR_TYPE_PALETTE) {
      png_set_palette_to_rgb(png_ptr);
   }
   
   /* Update the png info struct.*/
   png_read_update_info(png_ptr, info_ptr);

   /* Rowsize in bytes. */
   rowbytes = png_get_rowbytes(png_ptr, info_ptr);


   /* Allocate the image_data buffer. */
   if ((image_data = (unsigned char *) malloc(rowbytes * height))==NULL) {
      png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
      return 4;
    }

   if ((row_pointers = (png_bytepp)malloc(height*sizeof(png_bytep))) == NULL) {
        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
        free(image_data);
        image_data = NULL;
        return 4;
    }
   

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

    for (i = 0;  i < height;  ++i)
        row_pointers[height - 1 - i] = image_data + i*rowbytes;


    /* now we can go ahead and just read the whole image */
    png_read_image(png_ptr, row_pointers);

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

   /* Clean up. */
   free(row_pointers);

   /* Clean up. */
   png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
   fclose(infile);

   *image_data_ptr = image_data;

   return 1;
}