// Displays popi generated images on Plan9 4th/ed.
// Popi information can be found at:
// http://cm.bell-labs.com/cm/cs/who/gerard/
// 
// bugs are mine fst@centurytel.net

#include	<u.h>
#include	<libc.h>
#include	<draw.h>
#include	<event.h>
#include	<bio.h>
#define DEF_X	248	/* image width  */
#define DEF_Y	248	/* image height */

// Thresholds for halftone conversion from 8bit grayscale
// See "Beyond Photography, The digital Darkroom", G.J. Holtzmann
#define RES 8
uchar threshold[RES][RES] = {
	{ 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 },
	{ 12,140,44,172,4,132,36,164 },
	{ 204,76,236,108,196,68,228,100 },
	{ 60,188,28,156,52,180,20,148 },
	{ 252,124,220,92,244,116,212,84 }
};

void usage(void)
{
	fprint(2, "usage: disp [-h] imagefile\n");
	fprint(2, "\timagefile is generated by popi\n");
	exits("usage");
}

void eresized(int x)
{
}

int main(int argc, char **argv)
{
	Biobufhdr *infile;
	int nr, hflag = 0;
	uchar g8[DEF_Y * DEF_X];	/* grey scale buffer */
	uchar g1[DEF_Y * DEF_X/8];	/* halftone buffer, 1 bit per pixel*/
	Image *dpic;
	Event ev;
	Rectangle r, R = Rect(0,0,DEF_X,DEF_Y);

	ARGBEGIN {
	case 'h':		/* halftone display */
		hflag = 1;
		break;
	default:
		usage();
	} ARGEND

	if (argc < 1) {
		fprint(2, "imagefile missing\n");
		usage();
	}
	if (! (infile = Bopen(argv[0], OREAD))) {
		fprint(2, "can't open %s: %r\n", argv[0]);
		usage();
	}

	initdraw(nil, nil, "disp");
	einit(Ekeyboard|Emouse);

	dpic = allocimage(display, R, (hflag) ? GREY1 : GREY8, 1, DWhite);

	/* popi image files are DEF_Y×DEF_X×8bit grayscale pixels */
	nr = DEF_Y * DEF_X;
	if (Bread(infile, g8, nr) != nr) {
		fprint(2, "bad popi image file\n");
		usage();
	}

	if (hflag) {		/* halftone conversion */
		int y, x;

		memset(g1, 0, sizeof(g1));
		for (y = 0; y < DEF_Y; y++) {
			for (x = 0; x < DEF_X; x++) {
				int graypixloc = y * (DEF_Y) + x;
				int bwpixbyte = y * (DEF_Y/8) + x/8;

				if (g8[graypixloc] > threshold[y%RES][x%RES])
					g1[bwpixbyte] |= 0x80 >> x%8;
			}
		}
	}

	loadimage(dpic, R, (hflag) ? g1 : g8, nr);

	r = Rpt(screen->r.min, addpt(screen->r.min, Pt(DEF_X,DEF_Y)));
	draw(screen, r, dpic, nil, Pt(0,0));

	while(event(&ev) != Ekeyboard)
			;

	exits(0);
}