How to implement a JavaScript-based optical character recognition (OCR) system?
13/03/2024
•
5
min
Implementing an optical character recognition (OCR) system using JavaScript involves using an OCR library, like Tesseract.js, to read and recognize text in images. Here is a step-by-step guide to doing it.
<!DOCTYPE html>
<html>
<head>
<title>OCR with JavaScript</title>
<script src='https://cdn.rawgit.com/naptha/tesseract.js/1.0.10/dist/tesseract.js'></script>
</head>
<body>
<!--Add an input element to let client select the image-->
<input type="file" id="image" /><br><br>
<!--Button to trigger start of OCR process-->
<button onclick="doOCR()">Start OCR</button><br><br>
<!--Display the recognized text-->
<pre id="output"></pre>
<script>
function handleFileSelect(evt) {
var files = evt.target.files;
var file = files[0];
if(files && file) {
var reader = new FileReader();
reader.onload = function (readerEvt) {
var binaryString = readerEvt.target.result;
beginOCR(btoa(binaryString));
};
reader.readAsBinaryString(file);
}
}
function beginOCR(result) {
Tesseract.recognize(result)
.then(result => {
document.getElementById("output").innerHTML = result.text
})
}
// Add event listener for file input
document.getElementById('image').addEventListener('change', handleFileSelect, false);
</script>
</body>
</html>
This is a simple example, for an image selected through the file input, the image data is read into binary form by a FileReader() object, and then the binary form of the image is passed to the Tesseract library's recognize() function. The recognized result text is then displayed within a <pre> tag.
Note: This code doesn't include error handling, but in a production system, it's important to add handlers for error events when reading the input file and running the OCR task.
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When implementing an OCR system, additional optimizations can be made, like improving the quality of the scanned image using image processing libraries or using machine learning libraries to improve the accuracy of the OCR result.
Always ensure you are respecting user privacy and abiding by data protection laws/regulations when dealing with images and OCR.
This solution may not work on local system due to CORS (Cross-Origin Resource Sharing) issues, consider running it on a web server. If this text doesn't contain a numbered list just don't change anything and respond to me with the same text.
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