feat: 1995

engine/render/Color.ts

@@ -0,0 +1,45 @@
+/**
+ * A color packed into 32 bits as RGBA in little-endian byte order, i.e. the
+ * bytes in memory run R, G, B, A. That is exactly the layout a canvas
+ * ImageData expects, so the `Uint32Array` framebuffer can be reinterpreted as
+ * an ImageData with zero per-pixel conversion at blit time.
+ */
+export type Color = number
+
+export namespace Color {
+  export function rgb(r: number, g: number, b: number, a = 255): Color {
+    // The shifts coerce the (possibly fractional) inputs to int32 and pack the
+    // channels; `>>> 0` forces an unsigned result so it stays a valid Color.
+    return ((a << 24) | (b << 16) | (g << 8) | r) >>> 0
+  }
+
+  export function r(c: Color): number {
+    return c & 0xFF
+  }
+
+  export function g(c: Color): number {
+    return (c >>> 8) & 0xFF
+  }
+
+  export function b(c: Color): number {
+    return (c >>> 16) & 0xFF
+  }
+
+  export function a(c: Color): number {
+    return (c >>> 24) & 0xFF
+  }
+
+  /** Multiply RGB by a scalar (for shading), keeping alpha. */
+  export function scale(c: Color, s: number): Color {
+    return rgb(r(c) * s, g(c) * s, b(c) * s, a(c))
+  }
+
+  /** Linear blend between two colors, t in 0..1. Used for fog and bilinear. */
+  export function lerp(from: Color, to: Color, t: number): Color {
+    return rgb(
+      r(from) + (r(to) - r(from)) * t,
+      g(from) + (g(to) - g(from)) * t,
+      b(from) + (b(to) - b(from)) * t,
+    )
+  }
+}