readtif: fix many bugs

totif: add tiff encoder

sys/man/1/jpg

@@ -1,6 +1,6 @@
 .TH JPG 1
 .SH NAME
-jpg, gif, png, tif, ppm, bmp, v210, yuv, ico, tga, tojpg, togeordi, togif, toppm, topng, toico \- view and convert pictures
+jpg, gif, png, tif, ppm, bmp, v210, yuv, ico, tga, tojpg, togeordi, togif, toppm, topng, totif, toico \- view and convert pictures
 .SH SYNOPSIS
 .B jpg
 [
@@ -127,6 +127,16 @@ jpg, gif, png, tif, ppm, bmp, v210, yuv, ico, tga, tojpg, togeordi, togif, toppm
 ] [
 .I file
 ]
+.br
+.B totif
+[
+.B -c
+.I comment
+] [
+.B -bBgGhHlLmprtT
+] [
+.I file
+]
 .PP
 .B ico
 [
@@ -157,9 +167,11 @@ to Plan 9 image format and write them to standard output.
 .IR Tojpg ,
 .IR togif ,
 .IR toppm ,
+.IR topng ,
 and
-.I topng
+.I totif
-read Plan 9 images files, convert them to JPEG, GIF, PPM, or PNG, and write them to standard output.
+read Plan 9 images files, convert them to JPEG, GIF, PPM,
+PNG, or TIFF and write them to standard output.
 .PP
 The default behavior of
 .IR jpg ,
@@ -246,7 +258,7 @@ The
 and
 .IR topng
 programs go the other way: they convert from Plan 9 images to JPEG, GIF,
-PPM and PNG and have no display capability.
+PPM, PNG, and TIFF and have no display capability.
 They all accept an option
 .B -c
 to set the comment field of the resulting file.
@@ -270,6 +282,52 @@ is an
 script that invokes
 .B tojpg
 .BR -s .
+.I Totif
+accepts many options.
+Choosing Huffman, T4, or T6 compression
+forces the output to be a bilevel image.
+.TP
+.B -b
+Output a bilevel (GREY1) image.
+.TP
+.B -B
+Output a grayscale (GREY2) image.
+.TP
+.B -g
+Output a grayscale (GREY4) image.
+.TP
+.B -G
+Output a grayscale (GREY8) image.
+.TP
+.B -h
+Use Huffman compression.
+.TP
+.B -H
+Use T4 one-dimensional compression.
+.TP
+.B -l
+Use LZW compression.
+.TP
+.B -L
+Use LZW compression with horizontal differencing.
+Note that some TIFF decoders may not accept horizontal
+differencing applied to images with depths less than eight.
+.TP
+.B -m
+Output a color (CMAP8) image.
+.TP
+.B -p
+Use Packbits compression.
+.TP
+.B -r
+Output a color (BGR24) image.
+.TP
+.B -t
+Use T4 two-dimensional compression.
+.TP
+.B -T
+Use T6 compression.
+.PP
 If there is only one input picture,
 .I togif
 converts the image to GIF format.

sys/src/cmd/jpg/imagefile.h

@@ -75,10 +75,12 @@ Memimage*	memonechan(Memimage*);
 
 char*		writeppm(Biobuf*, Image*, char*, int);
 char*		memwriteppm(Biobuf*, Memimage*, char*, int);
+char*		writejpg(Biobuf*, Image*, char*, int, int);
+char*		memwritejpg(Biobuf*, Memimage*, char*, int, int);
 Image*		multichan(Image*);
 Memimage*	memmultichan(Memimage*);
 
 char*		memwritepng(Biobuf*, Memimage*, ImageInfo*);
 
-char*		writejpg(Biobuf*, Image*, char*, int, int);
+char*		writetif(Biobuf*, Image*, char*, int, int);
-char*		memwritejpg(Biobuf*, Memimage*, char*, int, int);
+char*		memwritetif(Biobuf*, Memimage*, char*, int, int);

sys/src/cmd/jpg/mkfile

@@ -10,6 +10,7 @@ TARG=\
 	png\
 	topng\
 	tif\
+	totif\
 	yuv\
 	ico\
 	toico\
@@ -54,9 +55,10 @@ $O.gif:		$IMFILES readgif.$O gif.$O
 $O.togif:	writegif.$O onechan.$O togif.$O torgbv.$O
 $O.ppm:		$IMFILES readppm.$O ppm.$O
 $O.toppm:	writeppm.$O multichan.$O toppm.$O
-$O.png:		$IMFILES readpng.$O png.$O
+$O.png:		torgbv.$O writerawimage.$O readpng.$O png.$O
 $O.topng:	writepng.$O topng.$O
-$O.tif:		$IMFILES readtif.$O tif.$O
+$O.tif:		torgbv.$O writerawimage.$O readtif.$O tif.$O
+$O.totif:	writetif.$O totif.$O
 $O.yuv:		$IMFILES readyuv.$O yuv.$O
 $O.bmp:		$IMFILES readbmp.$O bmp.$O
 $O.v210:	$IMFILES readv210.$O v210.$O

sys/src/cmd/jpg/readtif.c

@@ -7,7 +7,7 @@
 * http://www.itu.int/rec/T-REC-T.4-199904-S/en
 * http://www.itu.int/rec/T-REC-T.6-198811-I/en
 *
-* fax codes and lzw:
+* copy-pasted fax codes and lzw help:
 * http://www.remotesensing.org/libtiff/
 */
 #include <u.h>
@@ -91,9 +91,10 @@ struct Fax {
 	Tab *tab[2];
 	int ntab; /* position in tab */
 	Tab *eol;
+	int eolfill;
 	int (*getbit)(Fax *);
-	int *l1;
+	ulong *l1;
-	int *l2;
+	ulong *l2;
 	ulong nl;
 	uchar *data;
 	ulong next; /* next strip offset in data */
@@ -433,7 +434,7 @@ static void fillbits(Fax *);
 static int faxalloclines(Fax *);
 static Tab *getfax1d(Fax *, uchar *, ulong, ulong *, ulong *, ulong);
 static Tab *getfax2d(Fax *, uchar *, ulong, ulong *, ulong *, ulong);
-static int faxstrip(Tif *, Fax *, uchar *, ulong, ulong *);
+static int faxstrip(Tif *, Fax *, uchar *, ulong, ulong, ulong *);
 static uchar *fax(Tif *);
 static void tabinit(Lzw *);
 static Code *newcode(Lzw *, Code *);
@@ -441,7 +442,8 @@ static void listadd(Lzw *, Code *);
 static Code *tabadd(Lzw *, Code *, Code *);
 static int getcode(Lzw *);
 static int wstr(uchar *, ulong, ulong *, Code *, long *);
-static void predict(Tif *, uchar *);
+static int predict1(Tif *, uchar *, ulong);
+static int predict8(Tif *, uchar *, ulong);
 static int lzwstrip(Lzw *, uchar *, ulong, ulong *, long);
 static uchar *lzw(Tif *);
 static uchar *packbits(Tif *);
@@ -669,6 +671,10 @@ geteol(Fax *f)
 	Tab *p;
 
 	if(f->eol == nil) {
+		if(f->eolfill) {
+			for(i = 0; i < 4; i++)
+				(*f->getbit)(f);
+		}
 		if((p = gettab(f, 0)) == nil || p->run >= 0) {
 			werrstr("first eol");
 			return nil;
@@ -697,10 +703,8 @@ faxfill(Fax *f, uchar *data, ulong size, ulong *i, ulong *x, ulong dx,
 		werrstr("fax row overflow");
 		return -1;
 	}
-	if((*i += n) >= size) {
+	if((*i += n) > size)
-		werrstr("fax data overflow");
 		return -1;
-	}
 	if(f->st != 0)
 		memset(data+*i-n, f->st, n);
 	return 0;
@@ -744,7 +748,7 @@ getfax1d(Fax *f, uchar *data, ulong size, ulong *i, ulong *x,
 	int j, n;
 	Tab *p;
 
-	for(j = 0; *x < dx;) {
+	for(j = n = 0; *x < dx;) {
 		if((p = gettab(f, 0)) == nil)
 			return nil;
 		if((n = p->run) < 0) {
@@ -760,6 +764,17 @@ getfax1d(Fax *f, uchar *data, ulong size, ulong *i, ulong *x,
 		if(j >= f->nl)
 			faxalloclines(f);
 	}
+	if(n >= 64) {
+		f->l1[j] = dx;
+		if((p = gettab(f, 0)) == nil)
+			return nil;
+		if((n = p->run) < 0)
+			return f->eol;
+		if(n != 0) {
+			werrstr("no terminating code");
+			return nil;
+		}
+	}
 	return nil;
 }
 
@@ -767,7 +782,8 @@ static Tab *
 getfax2d(Fax *f, uchar *data, ulong size, ulong *i, ulong *x,
 	ulong dx)
 {
-	int j, k, n, code, len, a0, a1, b1, b2, v;
+	int j, k, n, code, len, v;
+	long a0, a1, b1, b2;
 	Tab *p;
 
 	a0 = -1;
@@ -795,7 +811,10 @@ getfax2d(Fax *f, uchar *data, ulong size, ulong *i, ulong *x,
 			for(k = 0; k < 2;) {
 				if((p = gettab(f, 0)) == nil)
 					return nil;
-				n = p->run;
+				if((n = p->run) < 0) {
+					werrstr("2d eol");
+					return nil;
+				}
 				if(faxfill(f, data, size, i, x,
 					dx, n) < 0)
 					return nil;
@@ -842,7 +861,8 @@ getfax2d(Fax *f, uchar *data, ulong size, ulong *i, ulong *x,
 }
 
 static int
-faxstrip(Tif *t, Fax *f, uchar *data, ulong size, ulong *i)
+faxstrip(Tif *t, Fax *f, uchar *data, ulong size, ulong rows,
+	ulong *i)
 {
 	int d1;
 	ulong x, y;
@@ -850,7 +870,7 @@ faxstrip(Tif *t, Fax *f, uchar *data, ulong size, ulong *i)
 
 	d1 = t->comp != T6enc;
 	p = nil;
-	for(x = y = 0; x < t->dx || y < t->rows;) {
+	for(x = y = 0; x < t->dx || y < rows;) {
 		f->st = 0;
 		if(t->comp == T4enc) {
 			if(p == nil && geteol(f) == nil) {
@@ -858,8 +878,11 @@ faxstrip(Tif *t, Fax *f, uchar *data, ulong size, ulong *i)
 					return -1;
 				break;
 			}
-			if(y > 0)
+			if(y > 0) {
 				*i += t->dx - x;
+				if(*i > size)
+					break;
+			}
 			if(t->t4 & 1) {
 				d1 = (*f->getbit)(f);
 				if(d1 < 0)
@@ -878,32 +901,34 @@ faxstrip(Tif *t, Fax *f, uchar *data, ulong size, ulong *i)
 		if(t->comp == Huffman)
 			fillbits(f);
 		if(p == nil && x != t->dx) {
-			if(f->st >= 0 || x > t->dx)
+			if(f->st >= 0)
+				return -1;
+			if(x > t->dx)
 				return -1;
 			break;
 		}
 	}
+	if(*i > size) {
+		werrstr("fax data overflow");
+		return -1;
+	}
 	return 0;
 }
 
-/*
+/* i've encountered t4 images that did not have rtcs */
-* the t4 fax test images i decoded did not follow the
-* spec. in particular, they did not have rtcs.
-*/
 static uchar *
 fax(Tif *t)
 {
 	int m;
-	ulong i, j, datasz, linesz;
+	ulong i, j, datasz, r, dy;
 	uchar *data;
 	Fax f;
 
 	datasz = t->dx * t->dy * sizeof *data;
-	data = malloc(datasz);
+	data = mallocz(datasz, 1);
-	f.nl = t->dx;
+	f.nl = t->dx + 1;
-	linesz = f.nl * sizeof *f.l1;
+	f.l1 = mallocz(f.nl*sizeof *f.l1, 1);
-	f.l1 = malloc(linesz);
+	f.l2 = mallocz(f.nl*sizeof *f.l2, 1);
-	f.l2 = malloc(linesz);
 	if(data == nil || f.l1 == nil || f.l2 == nil) {
 		free(t->data);
 		if(data != nil)
@@ -914,9 +939,6 @@ fax(Tif *t)
 			free(f.l2);
 		return nil;
 	}
-	memset(data, 0, datasz);
-	memset(f.l1, 0, linesz);
-	memset(f.l2, 0, linesz);
 	if(t->fill == 1) {
 		f.getbit = getbit1;
 		m = 7;
@@ -928,8 +950,12 @@ fax(Tif *t)
 	f.tab[1] = faxblack;
 	f.ntab = 0;
 	f.eol = nil;
+	if(t->comp == T4enc && t->t4 & (1<<1))
+		f.eolfill = 1;
+	else
+		f.eolfill = 0;
 	f.data = t->data;
-	for(i = j = 0; i < t->nstrips; i++) {
+	for(i = j = 0, dy = t->dy; i < t->nstrips; i++) {
 		f.l1[0] = t->dx;
 		f.n = t->strips[i];
 		f.m = m;
@@ -937,8 +963,10 @@ fax(Tif *t)
 			f.next = t->strips[i+1];
 		else
 			f.next = t->ndata;
-		if(faxstrip(t, &f, data, datasz, &j) < 0)
+		r = dy < t->rows? dy: t->rows;
+		if(faxstrip(t, &f, data, datasz, r, &j) < 0)
 			break;
+		dy -= t->rows;
 	}
 	if(i < t->nstrips) {
 		free(data);
@@ -993,20 +1021,20 @@ tabadd(Lzw *l, Code *p, Code *q)
 {
 	Code *r, *s;
 
-	if(l->ntab >= Tabsz) {
+	r = s = &l->tab[l->ntab];
-		werrstr("lzw table full");
-		return nil;
-	}
-	r = s = &l->tab[l->ntab++];
 	switch(l->ntab) {
-	case 511:
+	case 510:
-	case 1023:
+	case 1022:
-	case 2047:
+	case 2046:
 		l->len++;
 		break;
 	default:
 		break;
 	}
+	if(l->ntab++ >= Tabsz-3) {
+		werrstr("lzw table full");
+		return nil;
+	}
 	s->val = p->val;
 	while((p = p->next) != nil) {
 		if(s->next != nil)
@@ -1033,6 +1061,7 @@ getcode(Lzw *l)
 	int i, c, code;
 
 	if(l->n >= l->next) {
+eof:
 		werrstr("lzw eof");
 		return -1;
 	}
@@ -1042,8 +1071,9 @@ getcode(Lzw *l)
 		code |= c << i;
 		l->m--;
 		if(l->m < 0) {
-			l->n++;
 			l->m = 7;
+			if(++l->n >= l->next && i > 0)
+				goto eof;
 		}
 	}
 	return code;
@@ -1062,24 +1092,61 @@ wstr(uchar *data, ulong size, ulong *i, Code *p, long *striplen)
 	return 0;
 }
 
-static void
+static int
-predict(Tif *t, uchar *data)
+predict1(Tif *t, uchar *data, ulong ndata)
+{
+	int bpl, pix, b[8], d, m, n, j;
+	ulong i, x, y;
+
+	bpl = bytesperline(Rect(0, 0, t->dx, t->dy), t->depth);
+	d = t->depth;
+	m = (1 << d) - 1;
+	n = 8 / d;
+	for(y = 0; y < t->dy; y++) {
+		for(x = 0; x < bpl; x++) {
+			i = y*bpl + x;
+			if(i >= ndata) {
+				werrstr("pred4 overflow");
+				return -1;
+			}
+			pix = data[i];
+			b[n-1] = (pix >> d*(n-1)) & m;
+			if(x > 0)
+				b[n-1] += data[i-1] & m;
+			for(j = n-2; j >= 0; j--) {
+				b[j] = (pix >> d*j) & m;
+				b[j] += b[j+1];
+			}
+			for(j = pix = 0; j < n; j++)
+				pix |= (b[j] & m) << d*j;
+			data[i] = pix;
+		}
+	}
+	return 0;
+}
+
+static int
+predict8(Tif *t, uchar *data, ulong ndata)
 {
 	char a, b;
-	ulong y, x, i, j, k, s;
+	ulong i, j, s, x, y;
 
 	s = t->samples;
 	for(y = 0; y < t->dy; y++) {
 		for(x = 1; x < t->dx; x++) {
-			i = y*t->dx + x;
+			i = (y*t->dx + x) * s;
-			for(j = 0; j < s; j++) {
+			if(i+s-1 >= ndata) {
-				k = i*s + j;
+				werrstr("pred8 overflow");
-				a = (char)data[k];
+				return -1;
-				b = (char)data[k-s];
+			}
-				data[k] = (uchar)(a + b);
+			for(j = 0; j < s; i++, j++) {
+				a = (char)data[i];
+				b = (char)data[i-s];
+				data[i] = (uchar)(a + b);
 			}
 		}
 	}
+	return 0;
 }
 
 static int
@@ -1102,6 +1169,10 @@ lzwstrip(Lzw *l, uchar *data, ulong size, ulong *i, long striplen)
 				break;
 			if(c < 0)
 				return -1;
+			if(c >= l->ntab) {
+				werrstr("table overflow");
+				return -1;
+			}
 			if(wstr(data, size, i, &l->tab[c],
 				&striplen) < 0)
 				return -1;
@@ -1113,13 +1184,16 @@ lzwstrip(Lzw *l, uchar *data, ulong size, ulong *i, long striplen)
 			q = &l->tab[oc];
 			if(tabadd(l, q, p) == nil)
 				return -1;
-		} else {
+		} else if(c == l->ntab) {
 			q = &l->tab[oc];
 			if((p = tabadd(l, q, q)) == nil)
 				return -1;
 			if(wstr(data, size, i, p,
 				&striplen) < 0)
 				return -1;
+		} else {
+			werrstr("table overflow");
+			return -1;
 		}
 		if(striplen <= 0)
 			break;
@@ -1132,15 +1206,16 @@ lzwstrip(Lzw *l, uchar *data, ulong size, ulong *i, long striplen)
 static uchar *
 lzw(Tif *t)
 {
-	ulong i, j, size;
+	ulong i, j, size, r, dy, n;
 	long striplen;
 	uchar *data;
 	Lzw l;
 	Code *p, *q;
+	int (*predict)(Tif *, uchar *, ulong);
 
-	i = t->dx * t->rows * t->depth;
+	n = t->dx * t->dy * t->depth;
-	striplen = i%8 == 0? i/8: i/8+1;
+	n = n%8 == 0? n/8: n/8+1;
-	size = t->nstrips * striplen * sizeof *data;
+	size = n * sizeof *data;
 	if((data = malloc(size)) == nil) {
 		free(t->data);
 		return nil;
@@ -1151,7 +1226,7 @@ lzw(Tif *t)
 	}
 	l.data = t->data;
 	l.first = l.last = nil;
-	for(i = j = 0; i < t->nstrips; i++) {
+	for(i = j = 0, dy = t->dy; i < t->nstrips; i++) {
 		tabinit(&l);
 		l.n = t->strips[i];
 		l.m = 7;
@@ -1159,8 +1234,12 @@ lzw(Tif *t)
 			l.next = t->strips[i+1];
 		else
 			l.next = t->ndata;
+		r = dy < t->rows? dy: t->rows;
+		n = t->dx * r * t->depth;
+		striplen = n%8 == 0? n/8: n/8+1;
 		if(lzwstrip(&l, data, size, &j, striplen) < 0)
 			break;
+		dy -= t->rows;
 	}
 	if(i < t->nstrips) {
 		free(data);
@@ -1177,8 +1256,16 @@ lzw(Tif *t)
 		free(q);
 	}
 	free(t->data);
-	if(data != nil && t->predictor == 2)
+	if(data != nil && t->predictor == 2) {
-		predict(t, data);
+		if(t->depth < 8)
+			predict = predict1;
+		else
+			predict = predict8;
+		if((*predict)(t, data, size) < 0) {
+			free(data);
+			return nil;
+		}
+	}
 	return data;
 }
 
@@ -1189,7 +1276,9 @@ packbits(Tif *t)
 	ulong i, j, k, size;
 	uchar *data;
 
-	size = t->dx * t->dy * t->samples * sizeof *data;
+	i = t->dx * t->dy * t->depth;
+	i = i%8 == 0? i/8: i/8+1;
+	size = i * sizeof *data;
 	if((data = malloc(size)) == nil) {
 		free(t->data);
 		return nil;
@@ -1198,11 +1287,9 @@ packbits(Tif *t)
 		n = (char)t->data[i++];
 		if(n >= 0) {
 			k = n + 1;
-			if(j+k >= size || i+k >= t->ndata)
+			if((j += k) > size || (i += k) > t->ndata)
 				break;
-			memmove(data+j, t->data+i, k);
+			memmove(data+j-k, t->data+i-k, k);
-			i += k;
-			j += k;
 		} else if(n > -128 && n < 0) {
 			k = j - n + 1;
 			if(k > size || i >= t->ndata)
@@ -1461,18 +1548,18 @@ readfield(Tif *t, Fld *f)
 	size = typesizes[f->typ];
 	if((n = size*f->cnt) <= 4) {
 		for(i = 0; i < f->cnt; i++)
-			f->val[i] = readval(t);
+			f->val[i] = (*readval)(t);
 		f->off = 0x0;
 		f->nval = i;
 		for(j = n; j < 4; j += size)
-			readval(t);
+			(*readval)(t);
 	} else {
 		f->off = readlong(t);
 		off = t->n;
 		if(gototif(t, f->off) < 0)
 			return -1;
 		for(i = 0; i < f->cnt; i++)
-			f->val[i] = readval(t);
+			f->val[i] = (*readval)(t);
 		f->nval = i;
 		if(gototif(t, off) < 0)
 			return -1;
@@ -1600,10 +1687,6 @@ checkfields(Tif *t)
 		werrstr("color map");
 		return -1;
 	}
-	if(t->predictor == 2 && t->depth == 1) {
-		werrstr("depth too low for predictor 2");
-		return -1;
-	}
 	return 0;
 }
 
@@ -1613,9 +1696,14 @@ readstrips(Tif *t)
 	int i, j, n;
 	ulong off;
 
+	t->data = nil;
 	t->ndata = 0;
 	for(i = 0; i < t->nstrips; i++)
 		t->ndata += t->counts[i];
+	if(t->ndata == 0) {
+		werrstr("no image data");
+		return -1;
+	}
 	if((t->data = malloc(t->ndata*sizeof *t->data)) == nil)
 		return -1;
 	off = t->n;

sys/src/cmd/jpg/tif.c

@@ -169,17 +169,15 @@ show(int fd, char *name, int outchan)
 	if(array == nil || array[0] == nil) {
 		if(array != nil)
 			free(array);
-		fprint(2, "%s: decode %s failed: %r\n", argv0,
+		fprint(2, "%s: decode %s failed: %r\n",
-			name);
+			argv0, name);
 		return "decode";
 	}
 	Bterm(&b);
 	if(!dflag) {
 		if(init() < 0)
 			return "initdraw";
-/* fixme: ppm doesn't check for outchan==CMAP8 */
+		if(defaultcolor && screen->depth > 8)
-		if(defaultcolor && screen->depth > 8 &&
-			outchan == CMAP8)
 			outchan = RGB24;
 	}
 	r = array[0];
@@ -232,12 +230,10 @@ show(int fd, char *name, int outchan)
 				argv0, name);
 			return "write";
 		}
-	} else if(cflag) {
+	} else if(cflag && writerawimage(1, c) < 0) {
-		if(writerawimage(1, c) < 0) {
+		fprint(2, "%s: %s: write error: %r\n",
-			fprint(2, "%s: %s: write error: %r\n",
+			argv0, name);
-				argv0, name);
+		return "write";
-			return "write";
-		}
 	}
 	if(c != nil && c != r) {
 		free(c->chans[0]);

sys/src/cmd/jpg/totif.c

@@ -0,0 +1,157 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+#include <draw.h>
+#include <memdraw.h>
+#include "imagefile.h"
+
+static Memimage *memtochan(Memimage *, ulong);
+
+void
+usage(void)
+{
+	fprint(2, "usage: %s [-c 'comment'] "
+		"[-bBgGhHlLmprtT] [file]\n", argv0);
+	exits("usage");
+}
+
+void
+main(int argc, char *argv[])
+{
+	Biobuf bout;
+	Memimage *i, *ni;
+	int fd, chanflag, comp, opt;
+	char *err, *file, *c;
+	ulong chan;
+
+	chan = BGR24;
+	chanflag = opt = 0;
+	comp = 1;
+	c = nil;
+	ARGBEGIN {
+	case 'b':
+		chan = GREY1;
+		chanflag = 1;
+		break;
+	case 'B':
+		chan = GREY2;
+		chanflag = 1;
+		break;
+	case 'c':
+		c = EARGF(usage());
+		break;
+	case 'g':
+		chan = GREY4;
+		chanflag = 1;
+		break;
+	case 'G':
+		chan = GREY8;
+		chanflag = 1;
+		break;
+	case 'h': /* huffman */
+		comp = 2;
+		break;
+	case 'H': /* t4 */
+		comp = 3;
+		opt = 0;
+		break;
+	case 'l': /* lzw */
+		comp = 5;
+		opt = 0;
+		break;
+	case 'L': /* lzw, horizontal differencing */
+		comp = 5;
+		opt = 1;
+		break;
+	case 'm': /* palette */
+		chan = CMAP8;
+		chanflag = 1;
+		break;
+	case 'p': /* packbits */
+		comp = 0x8005;
+		break;
+	case 'r': /* force BGR24 */
+		chan = BGR24;
+		chanflag = 1;
+		break;
+	case 't': /* t4 two-dimensional */
+		comp = 3;
+		opt = 1;
+		break;
+	case 'T': /* t6 */
+		comp = 4;
+		break;
+	default:
+		usage();
+	} ARGEND
+	if(argc > 1)
+		usage();
+	if(argc == 0) {
+		file = "<stdin>";
+		fd = 0;
+	} else {
+		file = argv[0];
+		if((fd = open(file, OREAD)) < 0)
+			sysfatal("open %s: %r", file);
+	}
+	if(Binit(&bout, 1, OWRITE) < 0)
+		sysfatal("Binit: %r");
+	memimageinit();
+	if((i = readmemimage(fd)) == nil)
+		sysfatal("readmemimage %s: %r", file);
+	close(fd);
+	if(comp >= 2 && comp <= 4) {
+		chan = GREY1;
+		chanflag = 1;
+	} else if(chan == GREY2) {
+		if((ni = memtochan(i, chan)) == nil)
+			sysfatal("memtochan: %r");
+		if(i != ni) {
+			freememimage(i);
+			i = ni;
+		}
+		chan = GREY4;
+	}
+	if(!chanflag) {
+		switch(i->chan) {
+		case GREY1:
+		case GREY4:
+		case GREY8:
+		case CMAP8:
+		case BGR24:
+			break;
+		case GREY2:
+			chan = GREY4;
+			chanflag = 1;
+			break;
+		default:
+			chanflag = 1;
+			break;
+		}
+	}
+	if(chanflag) {
+		if((ni = memtochan(i, chan)) == nil)
+			sysfatal("memtochan: %r");
+		if(i != ni) {
+			freememimage(i);
+			i = ni;
+		}
+	}
+	if((err = memwritetif(&bout, i, c, comp, opt)) != nil)
+		fprint(2, "%s: %s\n", argv0, err);
+	freememimage(i);
+	exits(err);
+}
+
+static Memimage *
+memtochan(Memimage *i, ulong chan)
+{
+	Memimage *ni;
+
+	if(i->chan == chan)
+		return i;
+	if((ni = allocmemimage(i->r, chan)) == nil)
+		return nil;
+	memimagedraw(ni, ni->r, i, i->r.min, nil, i->r.min, S);
+	return ni;
+}