Support 4-bit grayscale in packtiles

software/scripts/packtiles

@@ -8,7 +8,7 @@ import sys
 
 FORMATS = [
 	"argb1555", "rgab5515", "bgar5515", "rgb565", "argb1232", "ragb2132", "rgb332",
-	"r8", "r6", "r2", "r1", "p8", "p4", "p2", "p1"
+	"r8", "r6", "r4", "r2", "r1", "p8", "p4", "p2", "p1"
 ]
 
 def bytes_from_bitstream_le(bitstream):
@@ -90,6 +90,7 @@ rgb_formats = {
 	"rgb332"  : (8, ((7, 5), (4, 2), (1, 0))),
 	"r8"      : (8, ((7, 0), (-1, 0), (-1, 0))),
 	"r6"      : (8, ((5, 0), (-1, 0), (-1, 0))),
+	"r4"      : (4, ((3, 0), (-1, 0), (-1, 0))),
 	"r2"      : (2, ((1, 0), (-1, 0), (-1, 0))),
 	"r1"      : (1, ((0, 0), (-1, 0), (-1, 0))),
 }