Incorporate a few upstream doc changes; grammar police; wordsmithing; Move -arithmetic into "switches for advanced users"; Additional documentation for IDCT scaling extensions

git-svn-id: svn://svn.code.sf.net/p/libjpeg-turbo/code/trunk@765 632fc199-4ca6-4c93-a231-07263d6284db

1 files changed, 13 insertions, 12 deletions

diff --git a/usage.txt b/usage.txt
index 7af75a8..4902c9b 100644
--- a/usage.txt
+++ b/usage.txt
@@ -131,7 +131,7 @@ quality-sensitive applications, for which the artifacts generated by
 subsampling may be unacceptable.
 
 The -quality option accepts a comma-separated list of parameters, which
-respectively refer to the quality levels which should be assigned to the
+respectively refer to the quality levels that should be assigned to the
 quantization table slots.  If there are more q-table slots than parameters,
 then the last parameter is replicated.  Thus, if only one quality parameter is
 given, this is used for both luminance and chrominance (slots 0 and 1,
@@ -157,6 +157,11 @@ file size is about the same --- often a little smaller.
 
 Switches for advanced users:
 
+	-arithmetic	Use arithmetic coding.  CAUTION: arithmetic coded JPEG
+			is not yet widely implemented, so many decoders will
+			be unable to view an arithmetic coded 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.
@@ -201,11 +206,6 @@ factor will visibly blur the image, however.
 
 Switches for wizards:
 
-	-arithmetic	Use arithmetic coding.  CAUTION: arithmetic coded JPEG
-			is not yet widely implemented, so many decoders will
-			be unable to view an arithmetic coded JPEG file at
-			all.
-
 	-baseline	Force baseline-compatible quantization tables to be
 			generated.  This clamps quantization values to 8 bits
 			even at low quality settings.  (This switch is poorly
@@ -250,10 +250,11 @@ The basic command line switches for djpeg are:
 			djpeg runs noticeably faster in this mode.
 
 	-scale M/N	Scale the output image by a factor M/N.  Currently
-			the scale factor must be 1/1, 1/2, 1/4, or 1/8.
-			Scaling is handy if the image is larger than your
-			screen; also, djpeg runs much faster when scaling
-			down the output.
+			the scale factor must be M/8, where M is an integer
+			between 1 and 16 inclusive, or any reduced fraction
+			thereof (such as 1/2, 3/4, etc.  Scaling is handy if
+			the image is larger than your screen; also, djpeg runs
+			much faster when scaling down the output.
 
 	-bmp		Select BMP output format (Windows flavor).  8-bit
 			colormapped format is emitted if -colors or -grayscale
@@ -447,9 +448,9 @@ To specify the coded JPEG representation used in the output file,
 jpegtran accepts a subset of the switches recognized by cjpeg:
 	-optimize	Perform optimization of entropy encoding parameters.
 	-progressive	Create progressive JPEG file.
+	-arithmetic	Use arithmetic coding.
 	-restart N	Emit a JPEG restart marker every N MCU rows, or every
 			N MCU blocks if "B" is attached to the number.
-	-arithmetic	Use arithmetic coding.
 	-scans file	Use the scan script given in the specified text file.
 See the previous discussion of cjpeg for more details about these switches.
 If you specify none of these switches, you get a plain baseline-JPEG output
@@ -527,7 +528,7 @@ markers, such as comment blocks:
 			present in the source file.
 	-copy comments	Copy only comment markers.  This setting copies
 			comments from the source file but discards
-			any other data which is inessential for image display.
+			any other data that is inessential for image display.
 	-copy all	Copy all extra markers.  This setting preserves
 			miscellaneous markers found in the source file, such
 			as JFIF thumbnails, Exif data, and Photoshop settings.