Added scanning barcodes with a camera

quagga2/quagga2-1.12.1/docs/tutorials/node-usage.md

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+# Using Quagga2 in Node.js {#node-usage}
+
+This tutorial covers server-side barcode scanning with Quagga2 in Node.js.
+
+## Installation {#installation}
+
+```bash
+npm install @ericblade/quagga2
+```
+
+## Basic Usage {#basic-usage}
+
+```javascript
+const Quagga = require('@ericblade/quagga2').default;
+
+Quagga.decodeSingle({
+  src: './barcode.jpg',
+  decoder: {
+    readers: ['code_128_reader', 'ean_reader']
+  }
+}, function(result) {
+  if (result && result.codeResult) {
+    console.log('Barcode:', result.codeResult.code);
+    console.log('Format:', result.codeResult.format);
+  } else {
+    console.log('No barcode found');
+  }
+});
+```
+
+## With Promises {#with-promises}
+
+Wrap in a Promise for async/await:
+
+```javascript
+const Quagga = require('@ericblade/quagga2').default;
+
+function decodeBarcode(imagePath, readers = ['code_128_reader']) {
+  return new Promise((resolve, reject) => {
+    Quagga.decodeSingle({
+      src: imagePath,
+      decoder: { readers }
+    }, (result) => {
+      if (result && result.codeResult) {
+        resolve(result.codeResult);
+      } else {
+        resolve(null);
+      }
+    });
+  });
+}
+
+// Usage
+async function main() {
+  const result = await decodeBarcode('./barcode.jpg');
+  if (result) {
+    console.log(`Found ${result.format}: ${result.code}`);
+  }
+}
+
+main();
+```
+
+## Express API Example {#express-example}
+
+```javascript
+const express = require('express');
+const multer = require('multer');
+const Quagga = require('@ericblade/quagga2').default;
+
+const app = express();
+const upload = multer({ dest: 'uploads/' });
+
+app.post('/scan', upload.single('image'), (req, res) => {
+  if (!req.file) {
+    return res.status(400).json({ error: 'No image provided' });
+  }
+
+  Quagga.decodeSingle({
+    src: req.file.path,
+    decoder: {
+      readers: ['code_128_reader', 'ean_reader', 'upc_reader']
+    }
+  }, (result) => {
+    if (result && result.codeResult) {
+      res.json({
+        code: result.codeResult.code,
+        format: result.codeResult.format
+      });
+    } else {
+      res.json({ code: null, error: 'No barcode found' });
+    }
+  });
+});
+
+app.listen(3000, () => {
+  console.log('Barcode API running on port 3000');
+});
+```
+
+## Batch Processing {#batch-processing}
+
+Process multiple images:
+
+```javascript
+const Quagga = require('@ericblade/quagga2').default;
+const fs = require('fs');
+const path = require('path');
+
+async function decodeImage(imagePath) {
+  return new Promise((resolve) => {
+    Quagga.decodeSingle({
+      src: imagePath,
+      decoder: { readers: ['code_128_reader', 'ean_reader'] }
+    }, (result) => {
+      resolve({
+        file: path.basename(imagePath),
+        code: result?.codeResult?.code || null,
+        format: result?.codeResult?.format || null
+      });
+    });
+  });
+}
+
+async function processDirectory(dir) {
+  const files = fs.readdirSync(dir)
+    .filter(f => /\.(jpg|jpeg|png)$/i.test(f));
+  
+  const results = [];
+  for (const file of files) {
+    const result = await decodeImage(path.join(dir, file));
+    results.push(result);
+    console.log(`${result.file}: ${result.code || 'No barcode'}`);
+  }
+  
+  return results;
+}
+
+processDirectory('./images');
+```
+
+## Configuration Tips {#configuration-tips}
+
+### Image Size {#image-size}
+
+Control processing resolution:
+
+```javascript
+Quagga.decodeSingle({
+  src: './large-image.jpg',
+  inputStream: {
+    size: 1280  // Scale to max 1280px
+  },
+  decoder: { readers: ['ean_reader'] }
+}, callback);
+```
+
+### Locator Settings {#locator-settings}
+
+For difficult images:
+
+```javascript
+Quagga.decodeSingle({
+  src: './image.jpg',
+  locate: true,
+  locator: {
+    patchSize: 'small',
+    halfSample: false
+  },
+  decoder: { readers: ['code_128_reader'] }
+}, callback);
+```
+
+## Related {#related}
+
+- [Static Image Scanning](static-image.md) - Browser-side image decoding
+- [API Reference](../reference/api.md#quagga-decodesingle) - `decodeSingle()` details
+- [Configuration Reference](../reference/configuration.md) - All options
+
+---
+
+[← Back to Tutorials](index.md)