feat(pixel): add FLOAT_GRAY_RANGE format

Author: postspectacular

packages/pixel/src/format/float-gray-range.ts

@@ -0,0 +1,28 @@
+import { fit, fitClamped } from "@thi.ng/math/fit";
+import { mix } from "@thi.ng/math/mix";
+import { FloatFormat, Lane } from "../api.js";
+import { __luminanceABGR } from "../internal/utils.js";
+
+/**
+ * Higher order, single channel float pixel format using provided [min..max]
+ * value range, instead of usual [0..1] interval.
+ *
+ * @param min
+ * @param max
+ */
+export const FLOAT_GRAY_RANGE = (min: number, max: number): FloatFormat => {
+	return {
+		__float: true,
+		alpha: false,
+		gray: true,
+		channels: [Lane.RED],
+		shift: { 3: 0 },
+		size: 1,
+		getNormalized: (val) => {
+			return fitClamped(val, min, max, 0, 1);
+		},
+		fromABGR: (src) => [mix(min, max, __luminanceABGR(src) / 255)],
+		toABGR: (src) =>
+			((fit(src[0], min, max, 0, 255) | 0) * 0x010101) | 0xff000000,
+	};
+};

packages/pixel/src/index.ts

@@ -27,6 +27,7 @@ export * from "./format/rgb888.js";
 export * from "./format/float-format.js";
 export * from "./format/float-gray.js";
 export * from "./format/float-gray-alpha.js";
+export * from "./format/float-gray-range.js";
 export * from "./format/float-hsva.js";
 export * from "./format/float-norm.js";
 export * from "./format/float-rgb.js";