LoadPng

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

typedef struct
{
   unsigned char* Data;
   unsigned int Width, Height;
   enum { RGB, RGBA } Type;
} Image;

BOOL LoadPng(char const* fileName, Image* image)
{
   FILE *fp = fopen(fileName, "rb");

   unsigned char header[8];
   if(fread(header, 1, 8, fp) != 8 || png_sig_cmp(header, 0, 8) != 0)
   {
      fclose(fp);
      return FALSE;
   }

   png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
   if(!png == NULL)
   {
      fclose(fp);
      return FALSE;
   }

   png_infop info = png_create_info_struct(png);
   if(info == NULL)
   {
      fclose(fp);
      png_destroy_read_struct(&png, NULL, NULL);
      return FALSE;
   }

   if(setjmp(png_jmpbuf(png)))
   {
      if(image->Data != NULL);
      {
         free(image->Data);
      }

      fclose(fp);
      png_destroy_read_struct(&png, &info, NULL);
      return FALSE;
   }

   png_init_io(png, fp);
   png_set_sig_bytes(png, 8); // Already read the first 8 bytes.
   png_read_png(png, info, PNG_TRANSFORM_STRIP_16 | PNG_TRANSFORM_PACKING | PNG_TRANSFORM_EXPAND, NULL);
   image->Width = png_get_image_width(png, info);
   image->Height = png_get_image_height(png, info);
   image->Type = png_get_color_type(png, info) == PNG_COLOR_TYPE_RGB ? RGB : RGBA;

   png_size_t stride = png_get_rowbytes(png, info);
   image->Data = malloc(stride * image->Height); // stride rather than width to take into account padding

   // Flipping the rows because OpenGL uses bottom left as origin
   png_bytepp rows = png_get_rows(png, info);
   for(unsigned int i = 0; i < image->Height; i++)
   {
      memcpy(image->Data + (stride * i), rows[image->Height - 1 - i], stride);
   }

   png_destroy_read_struct(&png, &info, NULL);
   fclose(fp);
   return TRUE;
}