From 2c57decd0d9063ab1a0b2abade2a985c380f0a7f Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Sat, 22 Aug 2026 17:20:05 +0200
Subject: [PATCH] Re-use `computeLuminance` in the
 `DOMFilterFactory.prototype.addHCMFilter` method

When the `addHCMFilter` method was added the helper function didn't exist, but now we can utilize it to avoid a tiny bit of code duplication.
---
 src/display/display_utils.js  |  1 +
 src/display/filter_factory.js | 15 +++++++++------
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/src/display/display_utils.js b/src/display/display_utils.js
index 7d9155319274a..658bbd8d4273d 100644
--- a/src/display/display_utils.js
+++ b/src/display/display_utils.js
@@ -829,6 +829,7 @@ function makePathFromDrawOPS(data) {
 export {
   applyOpacity,
   ColorScheme,
+  computeLuminance,
   CSSConstants,
   deprecated,
   fetchData,
diff --git a/src/display/filter_factory.js b/src/display/filter_factory.js
index 0819f811740ed..e0fc72ff87091 100644
--- a/src/display/filter_factory.js
+++ b/src/display/filter_factory.js
@@ -13,6 +13,12 @@
  * limitations under the License.
  */
 
+import {
+  computeLuminance,
+  getRGB,
+  getRGBA,
+  isDataScheme,
+} from "./display_utils.js";
 import {
   FeatureTest,
   SVG_NS,
@@ -21,7 +27,6 @@ import {
   Util,
   warn,
 } from "../shared/util.js";
-import { getRGB, getRGBA, isDataScheme } from "./display_utils.js";
 
 class BaseFilterFactory {
   constructor() {
@@ -277,11 +282,9 @@ class DOMFilterFactory extends BaseFilterFactory {
     // Then for every color in the pdf, if its rounded luminance is the
     // same as the background one then it's replaced by the new
     // background color else by the foreground one.
-    const map = new Array(256);
-    for (let i = 0; i <= 255; i++) {
-      const x = i / 255;
-      map[i] = x <= 0.03928 ? x / 12.92 : ((x + 0.055) / 1.055) ** 2.4;
-    }
+    const map = Array.from({ length: 256 }, (_, i) =>
+      computeLuminance(i / 255)
+    );
     const table = map.join(",");
 
     const id = `g_${this.#docId}_hcm_filter`;