131 lines
4.1 KiB
TypeScript
131 lines
4.1 KiB
TypeScript
import fc from "fast-check";
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import { describe, expect, it } from "vitest";
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import { compositeLayers, compositeSourceOver } from "../../src/colour";
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import type { BlendMode } from "../../src/colour";
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describe("source-over compositing", () => {
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it("matches the canonical translucent-red-over-white result", () => {
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const result = compositeSourceOver("rgba(255, 0, 0, .5)", "white");
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expect(result.colour.coords).toEqual([1, 0.5, 0.5]);
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expect(result.colour.alpha).toBe(1);
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expect(result.hex).toBe("#ff8080");
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});
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it("composites an arbitrary RGBA reference with the source-over equation", () => {
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const result = compositeSourceOver(
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"rgba(0, 129, 255, .42)",
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"rgb(255, 255, 255)",
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);
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expect(result.colour.coords[0]).toBeCloseTo(0.58, 12);
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expect(result.colour.coords[1]).toBeCloseTo(0.7924705882352941, 12);
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expect(result.colour.coords[2]).toBe(1);
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});
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it("supports N layers and an explicit stack order", () => {
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const layers = [
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{ colour: "white" },
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{ colour: "rgba(255,0,0,.5)" },
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{ colour: "rgba(0,0,255,.5)" },
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];
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expect(compositeLayers(layers).hex).toBe("#8040bf");
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expect(
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compositeLayers([...layers].reverse(), { order: "top-to-bottom" }).hex,
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).toBe("#8040bf");
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});
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it("offers visibly different sRGB and linear-light workflows", () => {
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const srgb = compositeSourceOver("rgba(255,0,0,.5)", "#00ff00", {
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space: "srgb",
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});
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const linear = compositeSourceOver("rgba(255,0,0,.5)", "#00ff00", {
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space: "linear-srgb",
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});
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expect(srgb.hex).toBe("#808000");
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expect(linear.hex).toBe("#bcbc00");
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});
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it("implements opacity and common blend modes", () => {
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expect(
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compositeSourceOver("#ff0000", "#808080", { blendMode: "multiply" }).hex,
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).toBe("#800000");
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expect(
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compositeSourceOver("#ff0000", "#808080", { blendMode: "screen" }).hex,
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).toBe("#ff8080");
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expect(compositeSourceOver("#ff0000", "#ffffff", { opacity: 0 }).hex).toBe(
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"#ffffff",
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);
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});
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it("keeps every exposed blend mode renderable", () => {
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const modes: BlendMode[] = [
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"normal",
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"multiply",
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"screen",
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"overlay",
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"darken",
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"lighten",
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"color-dodge",
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"color-burn",
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"hard-light",
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"soft-light",
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"difference",
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"exclusion",
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"hue",
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"saturation",
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"color",
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"luminosity",
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];
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for (const blendMode of modes) {
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const result = compositeSourceOver("rgba(230,30,80,.7)", "#2878c8", {
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blendMode,
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});
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expect(result.colour.coords.every(Number.isFinite), blendMode).toBe(true);
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expect(result.hex, blendMode).toMatch(/^#[0-9a-f]{6}$/);
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}
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});
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it("keeps arbitrary composites bounded and alpha-correct", () => {
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fc.assert(
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fc.property(
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fc.tuple(
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fc.double({ min: 0, max: 1, noNaN: true }),
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fc.double({ min: 0, max: 1, noNaN: true }),
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fc.double({ min: 0, max: 1, noNaN: true }),
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fc.double({ min: 0, max: 1, noNaN: true }),
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),
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fc.tuple(
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fc.double({ min: 0, max: 1, noNaN: true }),
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fc.double({ min: 0, max: 1, noNaN: true }),
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fc.double({ min: 0, max: 1, noNaN: true }),
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fc.double({ min: 0, max: 1, noNaN: true }),
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),
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(foreground, background) => {
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const result = compositeSourceOver(
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{
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space: "srgb",
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coords: foreground.slice(0, 3) as [number, number, number],
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alpha: foreground[3],
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},
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{
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space: "srgb",
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coords: background.slice(0, 3) as [number, number, number],
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alpha: background[3],
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},
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).colour;
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expect(
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result.coords.every((channel) => channel >= 0 && channel <= 1),
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).toBe(true);
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expect(result.alpha).toBeGreaterThanOrEqual(0);
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expect(result.alpha).toBeLessThanOrEqual(1);
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expect(result.alpha).toBeCloseTo(
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foreground[3] + background[3] * (1 - foreground[3]),
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12,
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);
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},
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),
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{ numRuns: 100 },
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);
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});
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});
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