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Auto Scan

Auto Scan lets the scanner drive the workflow: instead of calling scan() for every document, you enable auto-scan once and the scanner watches its paper sensor, automatically capturing each page as it is inserted. Captured images stream to the browser in real time.

This is ideal for high-throughput, hands-free workstations (mailrooms, check-in desks, batch document capture) where an operator feeds documents one after another.

How it works​

  1. Enable auto-scan with your desired scan settings.
  2. Listen to the auto-scan event stream. Each document scanned is delivered to your onImage callback as it is captured.
  3. Disable auto-scan when you are done.

Under the hood the SDK opens a Server-Sent Events connection to GET /api/twain/autoscan/events, so images arrive without polling.

Basic usage​

const scanner = new ASWCNScannerBridge();

// 1. Open a scanner
const sources = await scanner.getSources();
await scanner.openSource(sources[0].name);

// 2. Enable auto-scan (accepts the same parameters as scan())
await scanner.enableAutoScan({
    resolution: 300,
    colorMode: 'Color',
    autoCrop: true
});

// 3. Receive each document as it is scanned
const stream = await scanner.startAutoScan({
    onImage: (image) => {
        const img = document.createElement('img');
        img.src = `data:${image.mimeType};base64,${image.base64Data}`;
        document.getElementById('results').appendChild(img);
    },
    onDisabled: () => console.log('Auto-scan stopped'),
    onError: (err) => console.warn('Auto-scan stream error', err)
});

The image object delivered to onImage has the same shape as a normal scanned image, including ocrText and barcodes when those features are enabled.

Stopping​

Turn off auto-scan and close the stream when finished:

await scanner.disableAutoScan();
scanner.stopAutoScan(stream);

Calling disableAutoScan() also causes the server to emit a disabled event, which triggers your onDisabled handler and closes the stream automatically. Calling stopAutoScan(stream) on the client is still good practice to release the connection immediately.

Notes​

  • Open a scanner first. Auto-scan operates on the currently open source. If no source is open, enableAutoScan() returns an error.
  • One stream at a time. Open a single auto-scan event stream per page. Closing and reopening is fine, but avoid multiple concurrent streams.
  • Barcode and OCR work the same as in a normal scan — pass barcodeReadingEnabled: true or ocrEnabled: true to enableAutoScan() (both are premium features).
  • Connection drops. If the desktop app disconnects, the stream emits an error event and ends. Re-check checkServiceStatus() before re-enabling.

REST equivalent​

If you are not using the JavaScript SDK, the same flow is available over the REST API: POST /api/twain/autoscan/enable, GET /api/twain/autoscan/events (SSE), and POST /api/twain/autoscan/disable.