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);
     }

examples/hough.rs

@@ -2,20 +2,13 @@ mod common;
 
 use ccvl::*;
 
-const LINE: image::SRGBA = image::SRGBA {
-    r: 1.0,
-    g: 0.0,
-    b: 0.0,
-    a: 1.0,
-};
-
 fn main() -> std::process::ExitCode {
     common::process_image(|mut img| {
         let greyscale = img.map(|p| image::Luminance::from(p));
         let edges = filter::canny(greyscale);
         for line in hough::lines(10.0, edges) {
 			let ((x0, y0), (x1, y1)) = endpoints(line, img.extent);
-			draw::line(x0, y0, x1, y1, &mut img, LINE);
+			draw::line(x0, y0, x1, y1, &mut img, colours::RED);
         }
         img
     })

src/colours.rs

@@ -0,0 +1,21 @@
+use crate::*;
+
+macro_rules! hex {
+	( $value:literal ) => {
+		image::SRGBA {
+			r: (($value >> 16) & 0xff) as f32 / 255.0,
+			g: (($value >> 8) & 0xff) as f32 / 255.0,
+			b: ($value & 0xff) as f32 / 255.0,
+			a: 1.0,
+		}
+	}
+}
+
+pub const BLACK: image::SRGBA = hex!(0x000000);
+pub const RED: image::SRGBA = hex!(0xff0000);
+pub const GREEN: image::SRGBA = hex!(0x00ff00);
+pub const BLUE: image::SRGBA = hex!(0x0000ff);
+pub const CYAN: image::SRGBA = hex!(0x00ffff);
+pub const MAGENTA: image::SRGBA = hex!(0xff00ff);
+pub const YELLOW: image::SRGBA = hex!(0xffff00);
+pub const WHITE: image::SRGBA = hex!(0xffffff);

src/lib.rs

@@ -1,3 +1,4 @@
+pub mod colours;
 pub mod contour;
 pub mod draw;
 pub mod filter;