// Description:
//   Helper to save a SDL surface as a PNG.
//
// Copyright (C) 2001 Frank Becker
//
// This program is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free Software
// Foundation;  either version 2 of the License,  or (at your option) any  later
// version.
//
// This program is distributed in the hope that it will be useful,  but  WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details
//
#include <PNG.hpp>

//Save SDL surface as png
bool PNG::Save( SDL_Surface *img, const string &filename)
{
    FILE *fp = fopen( filename.c_str(), "wb");
    if( fp == NULL)
    {
	return false;
    }

    if( ! init( fp, img->w, img->h))
    {
        return false;
    }

    unsigned char *data =  (unsigned char *)img->pixels;
    for( int y=img->h-1; y>=0; y--)
    {
        png_bytep rowPointers = &data[ img->pitch*y];
        png_write_rows(_png, &rowPointers, 1);
    }

    close( fp);

    return true;
}

//write a chunk of png data
void PNG::writeData( png_structp png, png_bytep data, png_size_t length)
{
    png_uint_32 check;

    check = fwrite( data, 1, length, (FILE *)(png->io_ptr));
    if( check != length)
    {
	png_error( png, "Write Error");
    }
}

//init with file pointer and size of bitmap
bool PNG::init( FILE *fp, int width, int height)
{
    _png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL,NULL,NULL);

    if( _png == NULL)
    {
	fclose( fp);
	return false;
    }

    _info = png_create_info_struct(_png);

    if( _info == NULL)
    {
	fclose(fp);
	png_destroy_write_struct(&_png, (png_infopp)NULL);
	return false;
    }

    if( setjmp(_png->jmpbuf))
    {
	fclose( fp);
	png_destroy_write_struct(&_png, (png_infopp)NULL);
	return false;
    }

    png_set_write_fn(_png, (void *)fp, PNG::writeData, NULL);

    int colorType = PNG_COLOR_TYPE_RGB;
    if( _alpha) colorType = PNG_COLOR_TYPE_RGB_ALPHA;

    png_set_IHDR( _png, _info, width, height, 8 /*depth*/, colorType,
	    PNG_INTERLACE_NONE, 
	    PNG_COMPRESSION_TYPE_BASE, 
	    PNG_FILTER_TYPE_BASE);

    png_write_info( _png, _info);

    return true;
}

//close png file
void PNG::close( FILE *fp)
{
   png_write_end( _png, _info);
       
   png_destroy_write_struct( &_png, (png_infopp)NULL);
   
   fclose(fp);
}