[Question] How to change the image background ? Where to learn about web gl to master this project ?

[mystermiam]

I'd like to know how one could change the background image from the rain example Could you help with that. I've tried to by modifying the index.js file where textureRainBg and textureRainFg are created like so in the loadTextures function:

{ name: "textureRainFg", src: "img/weather/doc1.png" }

Doing so, i'm ending up with an error : "Failed to execute 'texImage2D' on 'WebGLRenderingContext': No function was found that matched the signature provided." I assumed the image i chose does not meet the requirements to use this function as its a jpeg transformed in a png by just changing the extension. Therefore, I've tried with proper png images, still same errors. Also I don't manage to see where this texImage2D function is called in the canvas creation process. Anyway, what one should use as an image to get it to work ? Where to learn about web gl to master this project ?

Many thanks.