t.Errorf("upperBound=%d: %v", upperBound, err)
			}
		} else {
			if err == nil {
				t.Errorf("upperBound=%d: got nil error, want non-nil", upperBound)
			}
		}
	}
}

func TestEncodeNonZeroMinPoint(t *testing.T) {
	points := []image.Point{
		{-8, -9},
		{-4, -4},
		{-3, +3},
		{+0, +0},
		{+2, +2},
	}
	for _, p := range points {
		src := image.NewPaletted(image.Rectangle{