Create colours module with colour definitions

examples/contours.rs

@@ -2,27 +2,14 @@ mod common;
 
 use ccvl::*;
 
-const OUTER: image::SRGBA = image::SRGBA {
-    r: 0.0,
-    g: 1.0,
-    b: 0.0,
-    a: 1.0,
-};
-const INNER: image::SRGBA = image::SRGBA {
-    r: 0.0,
-    g: 0.0,
-    b: 1.0,
-    a: 1.0,
-};
-
 fn draw(contour: &contour::Contour, img: &mut image::Image<image::SRGBA>) {
     let n = contour.vertices.len();
     for i in 0..n {
         let (x0, y0) = contour.vertices[i];
         let (x1, y1) = contour.vertices[(i + 1) % n];
         let colour = match contour.kind {
-            contour::Kind::Outer => OUTER,
-            contour::Kind::Inner => INNER,
+            contour::Kind::Outer => colours::GREEN,
+            contour::Kind::Inner => colours::BLUE,
         };
         draw::line(x0, y0, x1, y1, img, colour);
     }