#include "PngFunctions.h"

int PngColortypeFromSurface(SDL_Surface *surface)
{
	int colortype = PNG_COLOR_TYPE_RGB; // grayscale not supported

	if (surface->format->palette)
		colortype |= PNG_COLOR_TYPE_PALETTE;
	else if (surface->format->Amask)
		colortype |= PNG_COLOR_TYPE_RGB_ALPHA;
		
	return colortype;
}

void PngUserWarn(png_structp ctx, png_const_charp str)
{
	fprintf(stderr, "libpng: warning: %s\n", str);
}

void PngUserError(png_structp ctx, png_const_charp str)
{
	fprintf(stderr, "libpng: error: %s\n", str);
}

int PngSaveSurface(const char * filename, SDL_Surface *surf)
{
	FILE *fp;
	png_structp png_ptr;
	png_infop info_ptr;
	int i, colortype;
	png_bytep *row_pointers;

	// Opening output file
	if((fp = fopen(filename, "wb")) == NULL)
	{
		throw Exception("Screen", "fopen error");
		return -1;
	}

	// Initializing png structures and callbacks
	if((png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL,
	PngUserError, PngUserWarn)) == NULL)
	{
		throw Exception("Screen", "png_create_write_struct error!");
		return -1;
	}

	if((info_ptr = png_create_info_struct(png_ptr)) == NULL)
	{
		png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
		throw Exception("Screen", "png_create_info_struct error!");
		return -1;
	}

	if(setjmp(png_jmpbuf(png_ptr)))
	{
		png_destroy_write_struct(&png_ptr, &info_ptr);
		fclose(fp);
		throw Exception("Screen", "??");
		return -1;
	}

	png_init_io(png_ptr, fp);

	colortype = PngColortypeFromSurface(surf);
	png_set_IHDR(png_ptr, info_ptr, surf->w, surf->h, 8, colortype,	PNG_INTERLACE_NONE,
				PNG_COMPRESSION_TYPE_DEFAULT, PNG_FILTER_TYPE_DEFAULT);

	// Writing the image
	png_write_info(png_ptr, info_ptr);
	png_set_packing(png_ptr);

	row_pointers = (png_bytep*) malloc(sizeof(png_bytep)*surf->h);
	for (i = 0; i < surf->h; i++)
		row_pointers[i] = (png_bytep)(Uint8 *)surf->pixels + i*surf->pitch;

	png_write_image(png_ptr, row_pointers);
	png_write_end(png_ptr, info_ptr);

	// Cleaning out...
	free(row_pointers);
	png_destroy_write_struct(&png_ptr, &info_ptr);
	fclose(fp);

	return 0;
}