/* GDKSCale.c
 * Copyright(C) 2007 Akiyuki Kishiki
 */
#include<stdio.h>
#include<stdlib.h>
#include<gd.h>

enum{ SCALE = 2, MAX_DIPTH = 255 };

int gdImageD8ColorAllocate( gdImagePtr img, int d8_color )
{
	int red, grn, blu;
	red = ( ( d8_color >> 2 ) % 2 ) * MAX_DIPTH;
	grn = ( ( d8_color >> 1 ) % 2 ) * MAX_DIPTH;
	blu = ( ( d8_color >> 0 ) % 2 ) * MAX_DIPTH;
	return gdImageColorAllocate( img, red, grn, blu );
}

void gdKScaleGetXel( gdImagePtr dst, gdImagePtr src,
                     int x, int y, int bg_color )
{
	int center, over, under, left, right;
	int high1, high2, low1, low2;

	center = gdImageGetPixel( src, x, y );
	over  = ( y > 0 ) ? gdImageGetPixel( src, x, y - 1 )
	                  : bg_color; 
	under = ( y < gdImageSY( src ) - 1 )
	                  ? gdImageGetPixel( src, x, y + 1 )
	                  : bg_color; 
	left  = ( x > 0 ) ? gdImageGetPixel( src, x - 1, y )
	                  : bg_color; 
	right = ( x < gdImageSX( src ) - 1 )
	                  ? gdImageGetPixel( src, x + 1, y )
	                  : bg_color; 

	if( over == under || left == right )
		high1 = high2 = low1 = low2 = center;
	else{
		high1 = ( over  == left  ) ? over  : center;
		high2 = ( over  == right ) ? over  : center;
		low1  = ( under == left  ) ? under : center; 
		low2  = ( under == right ) ? under : center;
	}

	gdImageSetPixel( dst, x * SCALE,     y * SCALE,    high1 );
	gdImageSetPixel( dst, x * SCALE + 1, y * SCALE,    high2 );
	gdImageSetPixel( dst, x * SCALE,     y * SCALE + 1, low1 );
	gdImageSetPixel( dst, x * SCALE + 1, y * SCALE + 1, low2 );
}

gdImagePtr gdKScale( gdImagePtr src, int bg_color_d8 )
{
	gdImagePtr tmp, dst;
	int width, height, background;
	int x, y;

	width = gdImageSX( src );
	height = gdImageSY( src );
	tmp = gdImageCreateTrueColor( width, height );
	dst = gdImageCreateTrueColor( width * SCALE, height * SCALE );

	background = gdImageD8ColorAllocate( tmp, bg_color_d8 );
	gdImageFill( tmp, 0, 0, background );

	gdImageCopy( tmp, src, 0, 0, 0, 0, width, height );
	for( y = 0; y < height ; y++ )
		for( x = 0; x < width ; x++ )
			gdKScaleGetXel( dst, tmp, x, y, background );

	gdImageDestroy( tmp );
	return dst;
}

int main( int argc, char *argv[] )
{
	gdImagePtr im_src, im_dst;
	int bg_color_d8; /* 0(000: black) - 7(111: white) */

	if( argc > 0 ){
		bg_color_d8 = atoi( argv[1] );
		if( bg_color_d8 < 0 || bg_color_d8 > 7 )
			bg_color_d8 = 0;
	} else
		bg_color_d8 = 0;

	im_src = gdImageCreateFromPng( stdin );
	if( im_src == NULL ){
		fprintf( stderr, "not PNG File\n" );
		return 1;
	}

	im_dst = gdKScale( im_src, bg_color_d8 );

	gdImagePng( im_dst, stdout );

	fflush( stdout );

	gdImageDestroy( im_src );
	gdImageDestroy( im_dst );
}