diff --git a/js/msr_character.js b/js/msr_character.js
index 7663159..a55f918 100644
--- a/js/msr_character.js
+++ b/js/msr_character.js
@@ -57,6 +57,57 @@ function resolveCandidateImageUrls(originNode) {
   return urls;
 }
 
+async function blobToOptimizedDataUrl(blob, maxDim = 1024, quality = 0.82) {
+  const objectUrl = URL.createObjectURL(blob);
+  try {
+    const image = await new Promise((resolve, reject) => {
+      const img = new Image();
+      img.onload = () => resolve(img);
+      img.onerror = () => reject(new Error("Failed to decode image blob"));
+      img.src = objectUrl;
+    });
+
+    const width = image.naturalWidth || image.width || 0;
+    const height = image.naturalHeight || image.height || 0;
+    const scale = width > 0 && height > 0 ? Math.min(1, maxDim / Math.max(width, height)) : 1;
+    const targetWidth = Math.max(1, Math.round(width * scale)) || width || 1;
+    const targetHeight = Math.max(1, Math.round(height * scale)) || height || 1;
+
+    const canvas = document.createElement("canvas");
+    canvas.width = targetWidth;
+    canvas.height = targetHeight;
+    const ctx = canvas.getContext("2d");
+    if (!ctx) {
+      throw new Error("Could not acquire canvas context");
+    }
+    ctx.drawImage(image, 0, 0, targetWidth, targetHeight);
+
+    const optimizedBlob = await new Promise((resolve, reject) => {
+      canvas.toBlob((result) => {
+        if (result) resolve(result);
+        else reject(new Error("Canvas toBlob failed"));
+      }, "image/jpeg", quality);
+    });
+
+    const dataUrl = await new Promise((resolve) => {
+      const reader = new FileReader();
+      reader.onloadend = () => resolve(reader.result);
+      reader.readAsDataURL(optimizedBlob);
+    });
+
+    return {
+      dataUrl,
+      originalWidth: width,
+      originalHeight: height,
+      outputWidth: targetWidth,
+      outputHeight: targetHeight,
+      outputBytes: optimizedBlob.size || 0,
+    };
+  } finally {
+    URL.revokeObjectURL(objectUrl);
+  }
+}
+
 async function imageInputToDataUrl(node, inputName) {
   const originNode = getOriginNodeForInput(node, inputName);
   const candidateUrls = resolveCandidateImageUrls(originNode);
@@ -72,6 +123,11 @@ async function imageInputToDataUrl(node, inputName) {
         mimeType: null,
         blobBytes: 0,
         dataUrlLength: 0,
+        originalWidth: 0,
+        originalHeight: 0,
+        outputWidth: 0,
+        outputHeight: 0,
+        outputBytes: 0,
         error: "No candidate image URLs found",
       },
     };
@@ -87,11 +143,8 @@ async function imageInputToDataUrl(node, inputName) {
       if (!blob.type.startsWith("image/")) {
         throw new Error(`Unexpected blob type: ${blob.type || "unknown"}`);
       }
-      const dataUrl = await new Promise((resolve) => {
-        const reader = new FileReader();
-        reader.onloadend = () => resolve(reader.result);
-        reader.readAsDataURL(blob);
-      });
+      const optimized = await blobToOptimizedDataUrl(blob);
+      const dataUrl = optimized.dataUrl;
       return {
         dataUrl,
         debug: {
@@ -103,6 +156,11 @@ async function imageInputToDataUrl(node, inputName) {
           mimeType: blob.type || null,
           blobBytes: blob.size || 0,
           dataUrlLength: typeof dataUrl === "string" ? dataUrl.length : 0,
+          originalWidth: optimized.originalWidth,
+          originalHeight: optimized.originalHeight,
+          outputWidth: optimized.outputWidth,
+          outputHeight: optimized.outputHeight,
+          outputBytes: optimized.outputBytes,
           error: null,
         },
       };
@@ -122,6 +180,11 @@ async function imageInputToDataUrl(node, inputName) {
       mimeType: null,
       blobBytes: 0,
       dataUrlLength: 0,
+      originalWidth: 0,
+      originalHeight: 0,
+      outputWidth: 0,
+      outputHeight: 0,
+      outputBytes: 0,
       error: "All candidate image URLs failed",
     },
   };