Question

Technologies:

javascript

html

Tolerim

7 hours ago

What is the alternative to using cv.imencode?

In my code, I am encountering the error message "imencode is not a function" when using opencv.js. Specifically, the problem arises when calling the onOpenCvReady function as shown below:

function onOpenCvReady() {
    console.log('onOpenCvReady called');
    cv = window.cv;
    console.log('cv initialized');
}

Despite receiving the expected response in the Debugger, two logs indicating "onOpenCvReady called" and "cv initialized," I am still seeing the error message "Uncaught TypeError: cv.imencode is not a function" on the Debugger. I have tried using all available versions of opencv.js, but the issue remains unresolved. What can I do to resolve this issue? The problematic line in my code is as follows:

cv.imencode(".jpg", mat, encodedImage, params);

What is the alternate solution that I can use instead of cv.imencode?

Answers(1)

Accepted Answer

The cv.imencode function is not included in the opencv.js library. You can use the Canvas API to convert image data to a JPEG format instead. Here's an example of how you can achieve this:

function encodeJpeg(mat, quality) {
  var canvas = document.createElement('canvas');
  cv.imshow(canvas, mat);

  // Convert canvas to jpeg encoded data URL
  var dataUrl = canvas.toDataURL('image/jpeg', quality);

  // Extract encoded data from URL
  var encodedData = atob(dataUrl.split(',')[1]);

  // Convert data to Uint8Array
  var len = encodedData.length;
  var bytes = new Uint8Array(len);
  for (var i = 0; i < len; ++i) {
    bytes[i] = encodedData.charCodeAt(i);
  }

  return bytes;
}

In this example, we create a new canvas element and use cv.imshow to draw the OpenCV mat on it. We then convert the canvas to a JPEG encoded data URL using the toDataURL method. We extract the encoded data from the URL and convert it to a Uint8Array, which can be used for further processing. You can call this function like this:

var encodedImage = encodeJpeg(mat, 90);

This will generate a JPEG encoded image with a quality of 90%.