Bug with using getImageData

I’m creating a color picker and use the getImageData to get the color of the pixel where I click on it. It is not working when I run this code on WordPress environment. But it works when I use the exact same codes on other environment.

Try this out: https://jsfiddle.net/xob407fc/

P.S.: I’m sure the script is properly enqueue. There is no conflict of plugins. No error in the console, when you click the canvas, you always get rgb(0,0,0).