-d argument

kornelski · Sep 24, 2011 · c9be566 · c9be566
1 parent 7436b18
commit c9be566
Showing 1 changed file with 24 additions and 3 deletions.
diff --git a/posterize.c b/posterize.c
@@ -1,6 +1,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <assert.h>
 #include <math.h>
 #include "png.h"
@@ -167,13 +168,33 @@ void dither_palette(int* palette, int* palette2, int dither)
     }
 }
 
+void usage(const char *exepath)
+{
+    const char *name = strrchr(exepath, '/');
+    if (name) name++; else name = exepath;
+    fprintf(stderr, "Median Cut PNG Posterizer 1.1 (2011).\n" \
+            "Usage: %s [-d] levels\n\n" \
+            "Specify number of levels 2-255 as an argument. -d enables dithering\n" \
+            "Image is always read from stdin and written to stdout.\n"
+            "%s -d 16 < in.png > out.png\n", name, name);
+}
+
 int main(int argc, char *argv[])
 {
-    int maxcolors = argc == 2 ? atoi(argv[1]) : 0;
+    int argn=1;
     int dither=0;
+    if (argc==3 && 0==strcmp("-d", argv[1])) {
+        dither=1;
+        argn++;
+    }
+    int maxcolors=0;
+    if (argc==(argn+1)) {
+        maxcolors=atoi(argv[argn]);
+        argn++;
+    }
 
-    if (argc != 2 || maxcolors < 2 || maxcolors > 255) {
-        fprintf(stderr, "Median Cut PNG Posterizer 1.0 (2011).\n\nSpecify number of levels 2-255 as an argument.\nImage is read from stdin and written to stdout\n\n%s 16 < in.png > out.png\n", argv[0]);
+    if (argc != argn || maxcolors < 2 || maxcolors > 255) {
+        usage(argv[0]);
         return 1;
     }