glslwebglantialiasingalphablending

How do I fix the jaggedness and darkness around the edges of 2D textures in WebGL?

I've tried setting the antialias property on the WebGL context to true, but that didn't fix it.

This is what I'm getting in WebGL:

WebGL (what I'm getting)

This is canvas rendering, via drawImage, which is what I'm trying to replicate:

Canvas (what I want)

I'm using the default WebGL settings, aside from these three changed flags:

gl.enable(gl.BLEND); // Enable blending
gl.depthFunc(gl.LEQUAL); //near things obscure far things
gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA);

And here's how I load the sprites (with the sprite variable being an Image object)

const texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, sprite);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
Solution

  • Alright, fixed it. It was happening because my textures used premultiplied alpha values, which messed up the blending.

    I fixed it by changing my blendFunc from gl.blendFunc(gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA) to gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA)

    I also had to tell WebGL to unpack premultiplied alpha values by doing gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true)