improved SampleImageryToTilePyramids to only call GetFilteredColor for image layers which overlap the tile being sampled
improved SampleImageryToTilePyramids to only call GetFilteredColor for image layers which overlap the tile being sampled

nakijun/vtp,markraz/vtp,seanisom/vtp,seanisom/vtp,markraz/vtp,seanisom/vtp,nakijun/vtp,nakijun/vtp,seanisom/vtp,nakijun/vtp,nakijun/vtp,seanisom/vtp,markraz/vtp,markraz/vtp,markraz/vtp