Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!seismo!lll-crg!nike!sri-spam!parcvax!hplabs!pyramid!decwrl!amdcad!amdimage!cmoore
From: cmoore@amdimage.UUCP (chris moore)
Newsgroups: net.sources
Subject: Dithering for HP LaserJet
Message-ID: <111@amdimage.UUCP>
Date: Tue, 12-Aug-86 16:07:43 EDT
Article-I.D.: amdimage.111
Posted: Tue Aug 12 16:07:43 1986
Date-Received: Thu, 14-Aug-86 05:49:01 EDT
Organization: AMD Image Processing, Sunnyvale, CA
Lines: 101
Keywords: ray trace dither laserjet

The following is a modification of Steve Hawley's dithering
program modified to work on an HP LaserJet printer.  It
reads stdin and writes stdout, and doesn't take any arguments.
The input format is that used by Version 2.0 of Friedrich Knauss'
ray tracing program:  a one line header with a width and height,
followed by 8 bit pixel values.

			Chris Moore
			amdimage!cmoore

================CUT HERE ====================

#include <stdio.h>
#define WHITE 0
#define BLACK 1
#define ENDSCAN 2

int xsize,ysize;

main()
{
	int x,y,level;
	scanf("%d %d",&ysize,&xsize);
	printf("\033*t100R\n");
	printf("\033*r0A\n");
	for (x=0;x<xsize;x++) {
		for (y=0;y<ysize;y++) {
			level = getchar();
			if (dither(x, y, level)) makedot(WHITE);
			else makedot(BLACK);
		}
		makedot(ENDSCAN);
	}
	printf("\033*rB\n");
	
}
dither (x,y,level) /* dithering function */
register int x, y, level;
{
	 /* 8 x 8 dithering matrix */
	static int matrix[8][8] = {
	{  0,128, 32,160,  8,136, 40,168},
	{192, 64,224, 96,200, 72,232,104},
	{ 48,176, 16,144, 56,184, 24,152},
	{240,112,208, 80,248,120,216, 88},
	{ 12,140, 44,174,  4,132, 36,164},
	{204, 76,236,108,196, 68,228,100},
	{ 60,188, 28,156, 52,180, 20,148},
	{252,124,210, 92,244,116,212, 84}
	};



/* dithering by area access to matrix by using
	the MOD function on the x and y coordinates */
	return(level > matrix[x % 8][y % 8]);
}

makedot(color)
int color;
{
	static int	i,
			whichbyte = 0,
			whichbit = 0,
			nbytes,
			thisbyte = 0;

	nbytes = (ysize/8)+1;
	if (color == ENDSCAN) {
		/* end of scan line.  We have to send 'thisbyte',
		   and any other bytes required to make up a full
		   line (nbytes - whichbyte) */
		putchar(thisbyte);
		for (i=whichbyte+1;i<nbytes;i++) putchar(0);
		whichbyte = 0;
		whichbit = 0;
		thisbyte = 0;
	} else {
		if ((whichbyte == 0) & (whichbit == 0))
			printf("\033*b%dW",nbytes);
		thisbyte |= (color << (7 - whichbit++));
		if (whichbit > 7) {
			whichbyte++;
			whichbit = 0;
			putchar(thisbyte);
			thisbyte = 0;
		}
		if (whichbyte >= nbytes) {
			whichbyte = 0;
		}
	}
}

-- 

===========================================================
Any project can be built with a handful of parts if you have
big enough hands.

 Chris Moore (408) 749-4692
 UUCP: {ucbvax,decwrl,ihnp4,allegra}!amdcad!amdimage!cmoore