JSFiddle - React, Tailwind, and code Playground
HTML
<canvas id='C' width=800 height=600></canvas>
<canvas id='A' width=800 height=600 style='display:none'></canvas>
<canvas id='B' width=800 height=600 style='display:none'></canvas>
CSS
canvas {
border: 1px solid #ccc;
}
JavaScript
var sourceCanvas = document.getElementById('A');
var sourceTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, sourceTexture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, sourceCanvas);
// ...also set texture filters — see any WebGL tutorial...