The image is not clear after applying runtime shader

[pycxxx]

The first image is the original one, and the second image has a shader applied. Both are rendered on a Skia canvas.

Here is the code of the shader. It does nothing.

uniform shader image;

half4 main(float2 uv) {
  return image.eval(uv);
}

Does anyone know how this happens and how to fix it?

[pycxxx]

I found the answer :supersampling