From 85380f30a2e56b18fcc55d7e3c91b3a815b459be Mon Sep 17 00:00:00 2001
From: Kiradien <68683574+Kiradien@users.noreply.github.com>
Date: Sun, 2 Aug 2026 16:36:06 -0400
Subject: [PATCH] #2870 Enhanced animation detection

Overall enhancement to the detection of animated images. Code only runs when users wish to maintain animations, otherwise the function call immediately returns.
---
 plugin/_locales/en/messages.json |  4 ++++
 plugin/js/ImageCollector.js      | 35 +++++++++++++++++++++++++++++++-
 plugin/js/UserPreferences.js     |  1 +
 plugin/popup.html                |  8 +++++++-
 4 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/plugin/_locales/en/messages.json b/plugin/_locales/en/messages.json
index 716dcfa3..0a294fd3 100644
--- a/plugin/_locales/en/messages.json
+++ b/plugin/_locales/en/messages.json
@@ -267,6 +267,10 @@
 		"message": "Compress Images",
 		"description": "Label for checkbox and value to compress images to a certain size"
 	},
+	"__MSG_label_Compress_Images_Animated__": {
+		"message": "Compress Animated Images to single frame (GIF, APNG, WebP)",
+		"description": "Label for animated compression checkbox"
+	},
 	"__MSG_label_Compress_Images_JPG_Cover__": {
 		"message": "Restrict Cover Image to JPEG",
 		"description": "Label for JPEG cover restriction checkbox"
diff --git a/plugin/js/ImageCollector.js b/plugin/js/ImageCollector.js
index c5e76d46..3cfb225a 100644
--- a/plugin/js/ImageCollector.js
+++ b/plugin/js/ImageCollector.js
@@ -320,9 +320,42 @@ class ImageCollector {
         });
     }
 
+    isAnimatedImage(imageInfo) {
+        const animatedTypes = ["image/gif", "image/png", "image/webp"];
+
+        if (animatedTypes.includes(imageInfo.mediaType))
+        {
+            const maxScanBytes = 65536; 
+            const buffer = imageInfo.arraybuffer;
+            const scanLimit = Math.min(buffer.byteLength, maxScanBytes);
+            const view = new DataView(buffer, 0, scanLimit);
+            const limit = Math.max(0, view.byteLength - 4);
+
+            try {
+                for (let i = 0; i < limit; i++) {
+                    const current32 = view.getUint32(i, false);
+
+                    if ((imageInfo.mediaType == "image/webp" && (current32 === 0x414E494D || current32 === 0x414E4D46))
+                        || (imageInfo.mediaType == "image/png" && current32 === 0x6163544C)
+                        || (imageInfo.mediaType == "image/gif" && (current32 >>> 8) === 0x21F904)
+                    ) return true;
+                }
+            }
+            catch (e) {
+                console.error("Binary animation detection exception:", e);
+            }
+        }
+        return false;
+    }
+
+    skipAnimated(imageInfo) {
+        if (this.userPreferences.compressImagesAnimated.value) return false;
+        return this.isAnimatedImage(imageInfo);
+    }
+
     runCompression(imageInfo, img) {
         return new Promise((resolve, reject) => {
-            if (this.userPreferences.compressImages.value && imageInfo.mediaType != "image/gif") 
+            if (this.userPreferences.compressImages.value && !this.skipAnimated(imageInfo)) 
             {
                 let outputType = "image/jpeg";
                 switch (this.userPreferences.compressImagesType.value) {
diff --git a/plugin/js/UserPreferences.js b/plugin/js/UserPreferences.js
index 45c4674a..c5591e02 100644
--- a/plugin/js/UserPreferences.js
+++ b/plugin/js/UserPreferences.js
@@ -112,6 +112,7 @@ class UserPreferences { // eslint-disable-line no-unused-vars
         this.overrideMinimumDelay = this.addPreference("overrideMinimumDelay", "overrideMinimumDelayCheckbox", false);
         this.skipImages = this.addPreference("skipImages", "skipImagesCheckbox", false);
         this.compressImages = this.addPreference("compressImages", "compressImagesCheckbox", false);
+        this.compressImagesAnimated = this.addPreference("compressImagesAnimated", "compressImagesAnimatedCheckbox", true);
         this.compressImagesJpgCover = this.addPreference("compressImagesJpgCover", "compressImagesJpgCoverCheckbox", false);
         this.compressImagesType = this.addPreference("compressImagesType", "compressImagesType", "jpg");
         this.compressImagesMaxResolution = this.addPreference("compressImagesMaxResolution", "compressImagesMaxResolutionTag", "1080");
diff --git a/plugin/popup.html b/plugin/popup.html
index 44740ef4..6a2fb9db 100644
--- a/plugin/popup.html
+++ b/plugin/popup.html
@@ -1,4 +1,4 @@
-<!doctype html>
+<!doctype html>
 <html lang="en">
 <head>
     <meta charset="utf-8">
@@ -387,6 +387,12 @@ <h3>Instructions</h3>
                                 </td>
                                 <td>__MSG_label_Compress_Images_JPG_Cover__</td>
                             </tr>
+                            <tr>
+                                <td>
+                                    <input id="compressImagesAnimatedCheckbox" type="checkbox" name="compressImagesAnimated" value="true">
+                                </td>
+                                <td>__MSG_label_Compress_Images_Animated__</td>
+                            </tr>
                         </table>
                     </td>
                     </tr>