wip: Define RGB color transformations in shaders

packages/deck.gl-geotiff/src/webgl/cielab.glsl

@@ -0,0 +1,41 @@
+const vec3 D65 = vec3(
+    0.95047, // Xn
+    1.00000, // Yn
+    1.08883 // Zn
+);
+
+vec3 cielabToRgb(vec3 labTex) {
+    // labTex in [0,1] from RGB8 texture
+    float L = labTex.r * 255.0;
+    float a = (labTex.g - 0.5) * 255.0;
+    float b = (labTex.b - 0.5) * 255.0;
+
+    float y = (L + 16.0) / 116.0;
+    float x = (a / 500.0) + y;
+    float z = y - (b / 200.0);
+
+    vec3 xyz;
+    vec3 v = vec3(x, y, z);
+    vec3 v3 = v * v * v;
+
+    xyz = D65 * mix(
+        (v - 16.0 / 116.0) / 7.787,
+        v3,
+        step(0.008856, v3)
+    );
+
+    vec3 rgb = mat3(
+        3.2406, -1.5372, -0.4986,
+        -0.9689, 1.8758, 0.0415,
+        0.0557, -0.2040, 1.0570
+    ) * xyz;
+
+    // sRGB gamma
+    rgb = mix(
+        12.92 * rgb,
+        1.055 * pow(rgb, vec3(1.0 / 2.4)) - 0.055,
+        step(0.0031308, rgb)
+    );
+
+    return clamp(rgb, 0.0, 1.0);
+}

packages/deck.gl-geotiff/src/webgl/cmyk.glsl

@@ -0,0 +1,10 @@
+vec3 cmykToRgb(vec4 cmyk) {
+    // cmyk in [0.0, 1.0]
+    float invK = 1.0 - cmyk.a;
+
+    return vec3(
+        (1.0 - cmyk.r) * invK,
+        (1.0 - cmyk.g) * invK,
+        (1.0 - cmyk.b) * invK
+    );
+}

packages/deck.gl-geotiff/src/webgl/index.ts

@@ -0,0 +1,3 @@
+export { default as cmykToRgb } from "./cymk.glsl";
+export { default as ycbcrToRgb } from "./ycbcr.glsl";
+export { default as cielabToRgb } from "./cielab.glsl";

packages/deck.gl-geotiff/src/webgl/shims.d.ts

@@ -0,0 +1,4 @@
+declare module "*.glsl" {
+  const value: string;
+  export default value;
+}

packages/deck.gl-geotiff/src/webgl/ycbcr.glsl

@@ -0,0 +1,12 @@
+vec3 ycbcrToRgb(vec3 ycbcr) {
+    // ycbcr in [0.0, 1.0]
+    float y = ycbcr.r;
+    float cb = ycbcr.g - 0.5;
+    float cr = ycbcr.b - 0.5;
+
+    return vec3(
+        y + 1.40200 * cr,
+        y - 0.34414 * cb - 0.71414 * cr,
+        y + 1.77200 * cb
+    );
+}