debug: verify WebP blob data integrity and URL lifecycle

components/converter/ConversionPreview.tsx

@@ -46,12 +46,17 @@ export function ConversionPreview({ job, onDownload }: ConversionPreviewProps) {
   // Create preview URL for result
   React.useEffect(() => {
     if (job.result && job.status === 'completed') {
+      console.log('[Preview] Creating object URL for blob');
       const url = URL.createObjectURL(job.result);
       setPreviewUrl(url);
+      console.log('[Preview] Object URL created:', url);
 
       return () => {
+        console.log('[Preview] Revoking object URL:', url);
         URL.revokeObjectURL(url);
       };
+    } else {
+      setPreviewUrl(null);
     }
   }, [job.result, job.status]);
 

lib/converters/imagemagickService.ts

@@ -85,6 +85,10 @@ export async function convertWithImageMagick(
       quality: options.imageQuality,
     });
 
+    // Verify the data looks like valid image data by checking magic bytes
+    const first4Bytes = Array.from(result.slice(0, 4)).map(b => b.toString(16).padStart(2, '0')).join(' ');
+    console.log('[ImageMagick] First 4 bytes:', first4Bytes);
+
     // Create blob from result
     const mimeType = getMimeType(outputFormat);
     const blob = new Blob([result as BlobPart], { type: mimeType });
@@ -94,6 +98,25 @@ export async function convertWithImageMagick(
       type: blob.type,
     });
 
+    // Verify blob can be read
+    try {
+      const testReader = new FileReader();
+      const testPromise = new Promise((resolve) => {
+        testReader.onloadend = () => {
+          if (testReader.result instanceof ArrayBuffer) {
+            const testArr = new Uint8Array(testReader.result);
+            console.log('[ImageMagick] Blob verification - first 4 bytes:',
+              Array.from(testArr.slice(0, 4)).map(b => b.toString(16).padStart(2, '0')).join(' '));
+          }
+          resolve(true);
+        };
+      });
+      testReader.readAsArrayBuffer(blob.slice(0, 4));
+      await testPromise;
+    } catch (err) {
+      console.error('[ImageMagick] Blob verification failed:', err);
+    }
+
     if (onProgress) onProgress(100);
 
     const duration = Date.now() - startTime;