[PATCH] 200_crop_man.dpatch

Manpage update for jpegtran -crop

1 files changed, 37 insertions, 1 deletions

diff --git a/jpegtran.1 b/jpegtran.1
index 6de18e2..4e5b33c 100644
--- a/jpegtran.1
+++ b/jpegtran.1
@@ -131,6 +131,40 @@ followed by
 .B \-rot 180 -trim
 trims both edges.
 .PP
+If you are only interested by perfect transformation, add the
+.B \-perfect
+switch:
+.TP
+.B \-perfect
+Fails with an error if the transformation is not perfect. For example
+you may want to do
+.TP
+.B (jpegtran \-rot 90 -perfect foo.jpg || djpeg foo.jpg| pnmflip \-r90 | cjpeg)
+to do a perfect rotation if available or an approximated one if
+not.
+.PP
+We also offer a lossless-crop option, which discards data outside a given
+image region but losslessly preserves what is inside.  Like the rotate and
+flip transforms, lossless crop is restricted by the JPEG format: the upper
+left corner of the selected region must fall on an iMCU boundary.  If this
+does not hold for the given crop parameters, we silently move the upper left
+corner up and/or left to make it so, simultaneously increasing the region
+dimensions to keep the lower right crop corner unchanged.  (Thus, the
+output image covers at least the requested region, but may cover more.)
+
+Note: 
+.B \-perfect
+and
+.B lossless-crop
+are enhancements from http://sylvana.net/jpegcrop/ that may not be available on
+non-Debian systems.
+
+The image can be losslessly cropped by giving the switch:
+.TP
+.B \-crop WxH+X+Y
+Crop to a rectangular subarea of width W, height H starting at point X,Y.
+.PP
+.PP
 Another not-strictly-lossless transformation switch is:
 .TP
 .B \-grayscale
@@ -231,7 +265,9 @@ Arithmetic coding is not supported for legal reasons.
 .PP
 The transform options can't transform odd-size images perfectly.  Use
 .B \-trim
-if you don't like the results without it.
+or
+.B \-perfect
+if you don't like the results.
 .PP
 The entire image is read into memory and then written out again, even in
 cases where this isn't really necessary.  Expect swapping on large images,