From the docs:
"in jit.gl.pix the sample and nearest operators behave differently than with jit.pix . How a texture is sampled is determined by the properties of the texture. As a consequence, sample and nearest behave the same in jit.gl.pix . To enable nearest sampling, set the @filter attribute to nearest. For linear interpolation, set @filter to linear (the default)."
Not sure how to set the filter attribute.......