I'm trying to resize an image to a predefined size, keeping the aspect ratio of it. I've been using the following code to get the image data, but I don't know how to resize.
cropper.getCroppedCanvas().toDataURL('image/jpeg');
You can potentially use
cropper.getCroppedCanvas({ width: DESIRED_WIDTH, height: DESIRED_HEIGHT}).toDataURL(ORIGINAL_MIME_TYPE);
Its important to specify the original mime type of the image (png/gif etc) because otherwise you may end up with a significantly bigger image size in terms of file size.