From 7193457f36afc8b4d85c407b1e4d5723866baa3e Mon Sep 17 00:00:00 2001
From: Arne Baeumler <arne@br0tkasten.de>
Date: Sat, 13 Jun 2026 07:23:33 +0200
Subject: [PATCH] feat: generate client-side thumbnails

---
 src/server/request-handler.ts | 105 +++++++++++++++++++++++++++++++---
 1 file changed, 96 insertions(+), 9 deletions(-)

diff --git a/src/server/request-handler.ts b/src/server/request-handler.ts
index 14b173b..a7da8d1 100644
--- a/src/server/request-handler.ts
+++ b/src/server/request-handler.ts
@@ -1123,6 +1123,94 @@ function htmlPage(): string {
         })[character]);
       }
 
+      function buildRemoteImageUrl(shareUrlValue, entryHref) {
+        const params = new URLSearchParams({
+          share: shareUrlValue.trim(),
+          url: entryHref
+        });
+        return "/api/nextcloud/blob?" + params.toString();
+      }
+
+      async function loadImageElement(blob) {
+        const objectUrl = URL.createObjectURL(blob);
+        const image = new Image();
+
+        try {
+          await new Promise((resolve, reject) => {
+            image.onload = () => resolve();
+            image.onerror = () => reject(new Error("Could not decode image."));
+            image.src = objectUrl;
+          });
+          return image;
+        } finally {
+          URL.revokeObjectURL(objectUrl);
+        }
+      }
+
+      async function createThumbnailObjectUrl(blob) {
+        const maxDimension = 320;
+        const quality = 0.82;
+        let width = 0;
+        let height = 0;
+        let drawSource = null;
+        let closeBitmap = null;
+        let sourceImage = null;
+
+        if (typeof createImageBitmap === "function") {
+          const bitmap = await createImageBitmap(blob);
+          width = bitmap.width;
+          height = bitmap.height;
+          drawSource = bitmap;
+          closeBitmap = () => bitmap.close();
+        } else {
+          sourceImage = await loadImageElement(blob);
+          width = sourceImage.naturalWidth;
+          height = sourceImage.naturalHeight;
+          drawSource = sourceImage;
+        }
+
+        const scale = Math.min(1, maxDimension / Math.max(width, height));
+        const targetWidth = Math.max(1, Math.round(width * scale));
+        const targetHeight = Math.max(1, Math.round(height * scale));
+        const canvas = document.createElement("canvas");
+        const context = canvas.getContext("2d");
+
+        if (!context) {
+          if (closeBitmap) {
+            closeBitmap();
+          }
+          throw new Error("Canvas 2D context unavailable.");
+        }
+
+        canvas.width = targetWidth;
+        canvas.height = targetHeight;
+        context.drawImage(drawSource, 0, 0, targetWidth, targetHeight);
+
+        const thumbnailBlob = await new Promise((resolve, reject) => {
+          canvas.toBlob(
+            (result) => {
+              if (result) {
+                resolve(result);
+                return;
+              }
+              reject(new Error("Could not create thumbnail."));
+            },
+            "image/jpeg",
+            quality
+          );
+        });
+
+        if (closeBitmap) {
+          closeBitmap();
+        }
+
+        if (sourceImage) {
+          sourceImage.removeAttribute("src");
+        }
+
+        return URL.createObjectURL(thumbnailBlob);
+      }
+
       function setTheme(theme) {
         const resolvedTheme = theme === "light" ? "light" : "dark";
         document.body.dataset.theme = resolvedTheme;
@@ -1452,6 +1540,7 @@ function htmlPage(): string {
 
       function clearGallery() {
         cancelScheduledRender();
+        closeOverlayView();
         state.photos = [];
         state.visiblePhotos = [];
         state.activePhotoId = null;
@@ -1501,6 +1590,7 @@ function htmlPage(): string {
       function closeOverlayView() {
         overlay.classList.remove("open");
         overlay.setAttribute("aria-hidden", "true");
+        overlayImage.removeAttribute("src");
       }
 
       closeOverlay.addEventListener("click", closeOverlayView);
@@ -1950,11 +2040,8 @@ function htmlPage(): string {
       }
 
       async function readRemoteImage(entry, shareUrlValue, signal) {
-        const params = new URLSearchParams({
-          share: shareUrlValue.trim(),
-          url: entry.href
-        });
-        const response = await fetch("/api/nextcloud/blob?" + params.toString(), {
+        const fullUrl = buildRemoteImageUrl(shareUrlValue, entry.href);
+        const response = await fetch(fullUrl, {
           signal
         });
         if (!response.ok) {
@@ -1966,8 +2053,8 @@ function htmlPage(): string {
         const capturedAt =
           normalizeExifDate(tags?.DateTimeOriginal?.value ?? tags?.DateTimeOriginal) ||
           parseDateOrNull(entry.lastModified);
-        const objectUrl = URL.createObjectURL(blob);
-        state.objectUrls.push(objectUrl);
+        const thumbUrl = await createThumbnailObjectUrl(blob);
+        state.objectUrls.push(thumbUrl);
 
         return {
           id: entry.href,
@@ -1975,8 +2062,8 @@ function htmlPage(): string {
           latitude: gps?.latitude ?? null,
           longitude: gps?.longitude ?? null,
           capturedAt,
-          thumbUrl: objectUrl,
-          fullUrl: objectUrl,
+          thumbUrl,
+          fullUrl,
           source: "nextcloud"
         };
       }