X-Git-Url: https://rtime.felk.cvut.cz/gitweb/l4.git/blobdiff_plain/5a0e6ead0fbfbb912cd817abad695c078e82481c..8d9e85aaae867f39cdd610261e3a4181c25add2d:/l4/pkg/libjpeg/lib/contrib/usage.txt

diff --git a/l4/pkg/libjpeg/lib/contrib/usage.txt b/l4/pkg/libjpeg/lib/contrib/usage.txt
index 6e8546a6a..eae58425f 100644
--- a/l4/pkg/libjpeg/lib/contrib/usage.txt
+++ b/l4/pkg/libjpeg/lib/contrib/usage.txt
@@ -87,8 +87,9 @@ The basic command line switches for cjpeg are:
 	-progressive	Create progressive JPEG file (see below).
 
 	-scale M/N	Scale the output image by a factor M/N.  Currently
-			supported scale factors are 8/N with all N from 1 to
-			16.
+			supported scale factors are M/N with all N from 1 to
+			16, where M is the destination DCT size, which is 8 by
+			default (see -block N switch below).
 
 	-targa		Input file is Targa format.  Targa files that contain
 			an "identification" field will not be automatically
@@ -150,6 +151,19 @@ file size is about the same --- often a little smaller.
 
 Switches for advanced users:
 
+	-block N	Set DCT block size.  All N from 1 to 16 are possible.
+			Default is 8 (baseline format).
+			Larger values produce higher compression,
+			smaller values produce higher quality
+			(exact DCT stage possible with 1 or 2; with the
+			default quality of 75 and default Luminance qtable
+			the DCT+Quantization stage is lossless for N=1).
+			CAUTION: An implementation of the JPEG SmartScale
+			extension is required for this feature.  SmartScale
+			enabled JPEG is not yet widely implemented, so many
+			decoders will be unable to view a SmartScale extended
+			JPEG file at all.
+
 	-dct int	Use integer DCT method (default).
 	-dct fast	Use fast integer DCT (less accurate).
 	-dct float	Use floating-point DCT method.