How to toggle preserveDrawingBuffer in three.js?

Question

Basically, I want the setup where I could go to preserveDrawingBuffer=true, render the scene once, grab the screenshot, and go back. However, this poses two problems:

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Answer 1

I have also encountered this problem.my screenshot is blank in threejs webgl canvas, because not set renderer = new THREE.WebGLRenderer({canvas:renderer.domElement,preserveDrawingBuffer:true});, Here is my way to toggle preserveDrawingBuffer.

let canvas = this.renderer.domElement;
    canvas.getContext('webgl' , {preserveDrawingBuffer: true});
this.render();
var data = {
  image: canvas.toDataURL(),
};
canvas.getContext('webgl' , {preserveDrawingBuffer: false});