--- ray/src/px/paintjet.c	1989/10/20 20:36:13	1.3
+++ ray/src/px/paintjet.c	1991/05/06 13:14:26	1.6
@@ -48,7 +48,10 @@ char  *fname;
 		return(-1);
 	}
 				/* discard header */
-	getheader(input, NULL);
+	if (checkheader(input, COLRFMT, NULL) < 0) {
+		fprintf(stderr, "%s: not a Radiance picture\n", fname);
+		return(-1);
+	}
 				/* get picture dimensions */
 	if (fgetresolu(&xres, &yres, input) != (YMAJOR|YDECR)) {
 		fprintf(stderr, "%s: bad picture size\n", fname);
@@ -67,7 +70,7 @@ char  *fname;
 	for (i = yres-1; i >= 0; i--) {
 		if (freadcolrs(scanline, xres, input) < 0)
 			return(-1);
-		normcolrs(scanline, xres);
+		normcolrs(scanline, xres, 0);
 		plotscan(scanline, xres, i);
 	}
 
@@ -109,14 +112,16 @@ register int  x;
 register int  a;
 {
 	static int  cerr[NCOLS][3];
-	static int  err[3];
+	static int  err[3], errp[3];
 	int  b;
 	register int  ison;
 
 	b = col[a];
+	errp[a] = err[a];
 	err[a] += b + cerr[x][a];
 	ison = err[a] > 128;
 	if (ison) err[a] -= 256;
-	cerr[x][a] = err[a] /= 2;
+	err[a] /= 3;
+	cerr[x][a] = err[a] + errp[a];
 	return(ison);
 }