Changed bug in gamm4scanimage: When shadow==0 and highlight!=maxin then

then an endless loop occured.

Oliver Rauch

tools/gamma4scanimage.c

@@ -112,7 +112,7 @@ int main(int argc, char **argv)
     exit(-1);
   }
 
-  f = (highlight - shadow) / 255 + shadow;
+  f = (highlight - shadow) / 255.0 + shadow;
 
   printf("[%d]%d-", 0, 0);