fix missing -1 for top right corner, add example directory and update picture to readme

I also added example.sh, I think it could also be excluded.

README.md

@@ -9,7 +9,7 @@ Silicon is an alternative to [Carbon](https://github.com/dawnlabs/carbon) implem
 
 It can render your source code into a beautiful image.
 
-<img width="66%" src="http://storage.aloxaf.cn/silicon.png?v=2">
+<img width="66%" src="example/example.png">
 
 ## Why Silicon
 

example/example.rs

@@ -0,0 +1,10 @@
+fn factorial(n: u64) -> u64 {
+    match n {
+        0 => 1,
+        _ => n * factorial(n - 1),
+    }
+}
+
+fn main() {
+    println!("10! = {}", factorial(10));
+}

example/example.sh

@@ -0,0 +1 @@
+silicon example.rs -o example.png

src/utils.rs

@@ -303,7 +303,7 @@ pub(crate) fn round_corner(image: &mut DynamicImage, radius: u32) {
     image.copy_from(&*part, 0, 0).unwrap();
 
     // top right
-    let part = crop_imm(&circle, radius + 1, 1, radius, radius);
+    let part = crop_imm(&circle, radius + 1, 1, radius, radius - 1);
     image.copy_from(&*part, width - radius, 0).unwrap();
 
     // bottom left