--- ray/src/px/pfilt.c	1989/02/02 10:49:26	1.1
+++ ray/src/px/pfilt.c	1989/04/13 07:52:50	1.5
@@ -28,6 +28,9 @@ double  rad = 0.0;		/* output pixel radius for filteri
 int  nrows = 0;			/* number of rows for output */
 int  ncols = 0;			/* number of columns for output */
 
+double  x_c = 1.0;		/* ratio of output x size to input */
+double  y_r = 1.0;		/* ratio of output y size to input */
+
 int  singlepass = 0;		/* true means skip first pass */
 
 int  avghot = 0;		/* true means average in bright spots */
@@ -44,8 +47,6 @@ char  *tfname = NULL;
 
 int  xres, yres;		/* resolution of input */
 
-double  x_c, y_r;		/* conversion factors */
-
 int  xrad;			/* x window size */
 int  yrad;			/* y window size */
 
@@ -86,10 +87,20 @@ char  **argv;
 		if (argv[i][0] == '-')
 			switch (argv[i][1]) {
 			case 'x':
-				ncols = atoi(argv[++i]);
+				i++;
+				if (argv[i][0] == '/') {
+					x_c = 1.0/atof(argv[i]+1);
+					ncols = 0;
+				} else
+					ncols = atoi(argv[i]);
 				break;
 			case 'y':
-				nrows = atoi(argv[++i]);
+				i++;
+				if (argv[i][0] == '/') {
+					y_r = 1.0/atof(argv[i]+1);
+					nrows = 0;
+				} else
+					nrows = atoi(argv[i]);
 				break;
 			case 'e':
 				if (argv[i+1][0] == '+' || argv[i+1][0] == '-')
@@ -180,10 +191,14 @@ char  **argv;
 		fprintf(stderr, "%s: bad picture size\n", progname);
 		quit(1);
 	}
-	if (ncols <= 0)
-		ncols = xres;
-	if (nrows <= 0)
-		nrows = yres;
+	if (ncols > 0)
+		x_c = (double)ncols/xres;
+	else
+		ncols = x_c*xres + .5;
+	if (nrows > 0)
+		y_r = (double)nrows/yres;
+	else
+		nrows = y_r*yres + .5;
 
 	if (singlepass) {
 					/* skip exposure, etc. */
@@ -296,9 +311,6 @@ scan2init()			/* prepare scanline arrays */
 {
 	double  e;
 	register int  i;
-
-	x_c = (double)ncols/xres;
-	y_r = (double)nrows/yres;
 
 	if (rad <= 0.0) {
 		xrad = xres/ncols/2 + 1;