An auxiliary information map (10) is upsampled to form an upsampled auxiliary information map (20). Multiple reference pixels (23) in the upsampled auxiliary information map (20) are selected for a current pixel (21) in the upsampled auxiliary information map (20) based on texel values of texels in an associated texture (30). An updated pixel value is calculated for the current pixel (21) based on the pixel values of the selected reference pixels (23).