Add a function changeLightness in order to change the lightness of a RGB color

src/display/annotation_layer.js

@@ -37,7 +37,11 @@ import {
   Util,
   warn,
 } from "../shared/util.js";
-import { PDFDateString, setLayerDimensions } from "./display_utils.js";
+import {
+  changeLightness,
+  PDFDateString,
+  setLayerDimensions,
+} from "./display_utils.js";
 import { AnnotationStorage } from "./annotation_storage.js";
 import { ColorConverters } from "../shared/scripting_utils.js";
 import { DOMSVGFactory } from "./svg_factory.js";
@@ -232,46 +236,13 @@ class AnnotationElement {
     const opacity = this.data.opacity ?? 1;
     const oppositeOpacity = 255 * (1 - opacity);
 
-    return this.#changeLightness(
+    return changeLightness(
       Math.min(r + oppositeOpacity, 255),
       Math.min(g + oppositeOpacity, 255),
       Math.min(b + oppositeOpacity, 255)
     );
   }
 
-  #changeLightness(r, g, b) {
-    r /= 255;
-    g /= 255;
-    b /= 255;
-
-    const max = Math.max(r, g, b);
-    const min = Math.min(r, g, b);
-    const l = (max + min) / 2;
-    const newL = (((1 + Math.sqrt(l)) / 2) * 100).toFixed(2);
-
-    if (max === min) {
-      // gray
-      return `hsl(0, 0%, ${newL}%)`;
-    }
-
-    const d = max - min;
-
-    // hue (branch on max only; avoids mod)
-    let h;
-    if (max === r) {
-      h = (g - b) / d + (g < b ? 6 : 0);
-    } else if (max === g) {
-      h = (b - r) / d + 2;
-    } else {
-      // max === b
-      h = (r - g) / d + 4;
-    }
-    h = (h * 60).toFixed(2);
-    const s = ((d / (1 - Math.abs(2 * l - 1))) * 100).toFixed(2);
-
-    return `hsl(${h}, ${s}%, ${newL}%)`;
-  }
-
   _normalizePoint(point) {
     const {
       page: { view },

src/display/display_utils.js

@@ -770,7 +770,41 @@ const SupportedImageMimeTypes = [
   "image/x-icon",
 ];
 
+function changeLightness(r, g, b, lumCallback = l => (1 + Math.sqrt(l)) / 2) {
+  r /= 255;
+  g /= 255;
+  b /= 255;
+
+  const max = Math.max(r, g, b);
+  const min = Math.min(r, g, b);
+  const l = (max + min) / 2;
+  const newL = (lumCallback(l) * 100).toFixed(2);
+
+  if (max === min) {
+    // gray
+    return `hsl(0, 0%, ${newL}%)`;
+  }
+
+  const d = max - min;
+
+  // hue (branch on max only; avoids mod)
+  let h;
+  if (max === r) {
+    h = (g - b) / d + (g < b ? 6 : 0);
+  } else if (max === g) {
+    h = (b - r) / d + 2;
+  } else {
+    // max === b
+    h = (r - g) / d + 4;
+  }
+  h = (h * 60).toFixed(2);
+  const s = ((d / (1 - Math.abs(2 * l - 1))) * 100).toFixed(2);
+
+  return `hsl(${h}, ${s}%, ${newL}%)`;
+}
+
 export {
+  changeLightness,
   deprecated,
   fetchData,
   getColorValues,

src/pdf.js

@@ -52,6 +52,7 @@ import {
   version,
 } from "./display/api.js";
 import {
+  changeLightness,
   fetchData,
   getFilenameFromUrl,
   getPdfFilenameFromUrl,
@@ -98,6 +99,7 @@ globalThis.pdfjsLib = {
   AnnotationMode,
   AnnotationType,
   build,
+  changeLightness,
   ColorPicker,
   createValidAbsoluteUrl,
   DOMSVGFactory,
@@ -153,6 +155,7 @@ export {
   AnnotationMode,
   AnnotationType,
   build,
+  changeLightness,
   ColorPicker,
   createValidAbsoluteUrl,
   DOMSVGFactory,

test/unit/display_utils_spec.js

@@ -14,12 +14,14 @@
  */
 
 import {
+  changeLightness,
   getFilenameFromUrl,
   getPdfFilenameFromUrl,
+  getRGB,
   isValidFetchUrl,
   PDFDateString,
 } from "../../src/display/display_utils.js";
-import { toBase64Util } from "../../src/shared/util.js";
+import { isNodeJS, toBase64Util } from "../../src/shared/util.js";
 
 describe("display_utils", function () {
   describe("getFilenameFromUrl", function () {
@@ -300,4 +302,26 @@ describe("display_utils", function () {
       });
     });
   });
+
+  describe("changeLightness", function () {
+    it("Check that the lightness is changed correctly", function () {
+      if (isNodeJS) {
+        pending("DOM is not supported in Node.js.");
+      }
+      const div = document.createElement("div");
+      const { style } = div;
+      style.width = style.height = "0";
+      style.backgroundColor = "hsl(123, 45%, 67%)";
+      document.body.append(div);
+      const [r, g, b] = getRGB(getComputedStyle(div).backgroundColor);
+      div.remove();
+      expect([r, g, b]).toEqual([133, 209, 137]);
+      expect(changeLightness(r, g, b, l => l)).toEqual(
+        "hsl(123.16, 45.24%, 67.06%)"
+      );
+      expect(changeLightness(r, g, b, l => l / 2)).toEqual(
+        "hsl(123.16, 45.24%, 33.53%)"
+      );
+    });
+  });
 });

test/unit/pdf_spec.js

@@ -43,6 +43,7 @@ import {
   version,
 } from "../../src/display/api.js";
 import {
+  changeLightness,
   fetchData,
   getFilenameFromUrl,
   getPdfFilenameFromUrl,
@@ -82,6 +83,7 @@ const expectedAPI = Object.freeze({
   AnnotationMode,
   AnnotationType,
   build,
+  changeLightness,
   ColorPicker,
   createValidAbsoluteUrl,
   DOMSVGFactory,

web/comment_manager.js

@@ -15,6 +15,7 @@
 
 import {
   AnnotationEditorType,
+  changeLightness,
   getRGB,
   noContextMenu,
   PDFDateString,
@@ -355,9 +356,7 @@ class CommentManager {
       return null; // No color provided.
     }
     const [r, g, b] = getRGB(color);
-    const gray = (0.2126 * r + 0.7152 * g + 0.0722 * b) / 255;
-    const ratio = gray < 0.9 ? Math.round((0.9 - gray) * 100) : 0;
-    return `color-mix(in srgb, ${ratio}% white, ${color})`;
+    return changeLightness(r, g, b);
   }
 
   #setText(text) {

web/pdfjs.js

@@ -23,6 +23,7 @@ const {
   AnnotationMode,
   AnnotationType,
   build,
+  changeLightness,
   ColorPicker,
   createValidAbsoluteUrl,
   DOMSVGFactory,
@@ -78,6 +79,7 @@ export {
   AnnotationMode,
   AnnotationType,
   build,
+  changeLightness,
   ColorPicker,
   createValidAbsoluteUrl,
   DOMSVGFactory,