/* Listing 3: Code to form a horizontal motion blur

Blurs a monochrome 8 bit image in "src" of dimensions src_w x src_h,
outputs to dst. The amount of blur is set by boxw */

void DoHorizBlur(UBYTE *src, int src_w, int src_h, UBYTE *dst, int boxw)
{
	if (boxw<0)
	{
		memcpy(dst,src,src_w*src_h); // deal with degenerate kernel sizes
		return;
	}
	if (boxw>=src_w) boxw=src_w-1;
	float mul=1.f/(boxw*2+1);
	for (int y=0;y<src_h;y++)
	{
		int tot=0;
		for (int x=0;x<boxw;x++) tot+=src[x];
		for (x=0;x<src_w;x++)
		{
			if (x>boxw) tot-=src[-boxw-1];
			if (x+boxw<src_w) tot+=src[boxw];
			*dst++=UBYTE(tot*mul);
			src++;
		}
	}	
}