library: texture: add UniformTexture implementation

src/texture/mod.rs

@@ -6,3 +6,6 @@ pub trait Texture: std::fmt::Debug {
     /// Get the color at a given texel coordinate
     fn texel_color(&self, point: Point2D) -> LinearColor;
 }
+
+pub mod uniform;
+pub use uniform::*;

src/texture/uniform.rs

@@ -0,0 +1,45 @@
+use super::super::core::LinearColor;
+use super::super::Point2D;
+use super::Texture;
+
+/// A texture with the same color on all points.
+#[derive(Debug, PartialEq)]
+pub struct UniformTexture {
+    color: LinearColor,
+}
+
+impl UniformTexture {
+    pub fn new(color: LinearColor) -> Self {
+        UniformTexture { color }
+    }
+}
+
+impl Texture for UniformTexture {
+    fn texel_color(&self, _: Point2D) -> LinearColor {
+        self.color.clone()
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn new_works() {
+        let color = LinearColor::new(0.2, 0.4, 0.6);
+        let texture = UniformTexture::new(color.clone());
+        assert_eq!(texture, UniformTexture { color })
+    }
+
+    fn simple_texture() -> UniformTexture {
+        UniformTexture::new(LinearColor::new(0.25, 0.5, 1.))
+    }
+    #[test]
+    fn texel_color_works() {
+        let texture = simple_texture();
+        assert_eq!(
+            texture.texel_color(Point2D::origin()),
+            LinearColor::new(0.25, 0.5, 1.)
+        )
+    }
+}