Create greyscale example

examples/greyscale.rs

@@ -1,4 +1,8 @@
-use ccvl::{image::*, kernel::*};
+use ccvl::image::*;
+
+fn filter(img: Image<SRGBA>) -> Image<SRGBA> {
+    img.map(|p| Luminance::from(p).into())
+}
 
 fn main() -> std::process::ExitCode {
     let args = std::env::args().collect::<Vec<String>>();
@@ -19,20 +23,12 @@ fn main() -> std::process::ExitCode {
             println!("I/O error loading image {}: {}", input_path, err);
             std::process::ExitCode::FAILURE
         }
-        Ok(img) => {
-            let kernel =
-                [[1.0, 1.0, 1.0], [1.0, 1.0, 1.0], [1.0, 1.0, 1.0]];
-            let result = kernel.convolve(&img);
-            match result.save::<Farbfeld>(output_path) {
+        Ok(img) => match filter(img).save::<Farbfeld>(output_path) {
             Err(err) => {
-                    println!(
-                        "I/O error saving image {}: {}",
-                        output_path, err
-                    );
+                println!("I/O error saving image {}: {}", output_path, err);
                 std::process::ExitCode::FAILURE
             }
             Ok(()) => std::process::ExitCode::SUCCESS,
-            }
-        }
+        },
     }
 }