nice try ?

Fonderie/crapulator.c

@@ -105,7 +105,7 @@ FimgFilter3x3	diagonal = {
 		1.0,	0.0,	-1.0,
 		0.0,	-1.0,	-2.0,
 		},
-	1.0,	4.0
+	1.0,	0.0
 	};
 
 switch (typef) {
@@ -126,6 +126,7 @@ if (retval) {
 	fprintf(stderr, "%s error %d on filter\n", __func__, retval);
 	exit(1);
 	}
+(void)fimg_killborders(&img);			/* nice try ? */
 
 foo = fimg_auto_shift_to_zero(&img, &img);
 if (foo) {