debug message for bad pixels

src/image.rs

@@ -12,7 +12,9 @@ impl From<String> for Image {
         let pixels = &pixels[1..(pixels.len() - 1)];
         let pixels: Vec<u32> = pixels
             .iter()
-            .map(|&pixel| pixel.parse::<u32>().unwrap())
+            .map(|&pixel|
+                pixel.parse::<u32>().expect(&format!("Bad pixel in image: {}\n", pixel))
+            )
             .collect();
 
         Image { pixels }