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demo_cam_reader.html
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<!DOCTYPE html>
<html>
<head>
<title>zxing-cpp/wasm live demo</title>
<link rel="shortcut icon" href="#" />
<script src="zxing_reader.js"></script>
</head>
<body style="text-align: center">
<h2>zxing-cpp/wasm live demo</h2>
<p>
This is a simple demo of the wasm wrapper of <a href="https://github.com/zxing-cpp/zxing-cpp">zxing-cpp</a>
scanning for barcodes in a live video stream.
</p>
Camera:
<select id="cameraSelector">
<option value="user">Front Camera</option>
<option value="environment">Back Camera</option>
</select>
Format:
<select id="format">
<option value="" selected="">Any</option>
<option value="Aztec">Aztec</option>
<option value="Code39">Codabar</option>
<option value="CODE_39">Code39</option>
<option value="Code93">Code93</option>
<option value="Code128">Code128</option>
<option value="DataMatrix">DataMatrix</option>
<option value="DataBar">DataBar</option>
<option value="DataBarExpanded">DataBarExpanded</option>
<option value="DataBarLimited">DataBarLimited</option>
<option value="DXFilmEdge">DXFilmEdge</option>
<option value="EAN8">EAN-8</option>
<option value="EAN13">EAN-13</option>
<option value="ITF">ITF</option>
<option value="PDF417">PDF417</option>
<option value="QRCode">QRCode</option>
<option value="MicroQRCode">Micro QRCode</option>
<option value="RMQRCode">rMQR Code</option>
<option value="UPCA">UPC-A</option>
<option value="UPCE">UPC-E</option>
<option value="LinearCodes">Linear Codes</option>
<option value="MatrixCodes">Matrix Codes</option>
</select>
Mode:
<select id="mode">
<option value="true" selected="">Normal</option>
<option value="false">Fast</option>
</select>
<br /><br />
<canvas id="canvas" width="640" height="480"></canvas>
<br /><br />
<div id="result"></div>
<script>
var zxing = ZXing().then(function (instance) {
zxing = instance; // this line is supposedly not required but with current emsdk it is :-/
});
const cameraSelector = document.getElementById("cameraSelector");
const format = document.getElementById("format");
const mode = document.getElementById("mode");
const canvas = document.getElementById("canvas");
const resultElement = document.getElementById("result");
const ctx = canvas.getContext("2d", { willReadFrequently: true });
const video = document.createElement("video");
video.setAttribute("id", "video");
video.setAttribute("width", canvas.width);
video.setAttribute("height", canvas.height);
video.setAttribute("autoplay", "");
function readBarcodeFromCanvas(canvas, format, mode) {
var imgWidth = canvas.width;
var imgHeight = canvas.height;
var imageData = canvas.getContext('2d').getImageData(0, 0, imgWidth, imgHeight);
var sourceBuffer = imageData.data;
if (zxing != null) {
var buffer = zxing._malloc(sourceBuffer.byteLength);
zxing.HEAPU8.set(sourceBuffer, buffer);
var result = zxing.readBarcodeFromPixmap(buffer, imgWidth, imgHeight, mode, format);
zxing._free(buffer);
return result;
} else {
return { error: "ZXing not yet initialized" };
}
}
function drawResult(code) {
ctx.beginPath();
ctx.lineWidth = 4;
ctx.strokeStyle = "red";
// ctx.textAlign = "center";
// ctx.fillStyle = "#green"
// ctx.font = "25px Arial";
// ctx.fontWeight = "bold";
with (code.position) {
ctx.moveTo(topLeft.x, topLeft.y);
ctx.lineTo(topRight.x, topRight.y);
ctx.lineTo(bottomRight.x, bottomRight.y);
ctx.lineTo(bottomLeft.x, bottomLeft.y);
ctx.lineTo(topLeft.x, topLeft.y);
ctx.stroke();
// ctx.fillText(code.text, (topLeft.x + bottomRight.x) / 2, (topLeft.y + bottomRight.y) / 2);
}
}
function escapeTags(htmlStr) {
return htmlStr.replace(/&/g, "&").replace(/</g, "<").replace(/>/g, ">").replace(/"/g, """).replace(/'/g, "'");
}
const processFrame = function () {
ctx.drawImage(video, 0, 0, canvas.width, canvas.height);
const code = readBarcodeFromCanvas(canvas, format.value, mode.value === 'true');
if (code.format) {
resultElement.innerText = code.format + ": " + escapeTags(code.text);
drawResult(code)
} else {
resultElement.innerText = "No barcode found";
}
requestAnimationFrame(processFrame);
};
const updateVideoStream = function (deviceId) {
// To ensure the camera switch, it is advisable to free up the media resources
if (video.srcObject) video.srcObject.getTracks().forEach(track => track.stop());
navigator.mediaDevices
.getUserMedia({ video: { facingMode: deviceId }, audio: false })
.then(function (stream) {
video.srcObject = stream;
video.setAttribute("playsinline", true); // required to tell iOS safari we don't want fullscreen
video.play();
processFrame();
})
.catch(function (error) {
console.error("Error accessing camera:", error);
});
};
cameraSelector.addEventListener("change", function () {
updateVideoStream(this.value);
});
updateVideoStream();
</script>
</body>
</html>