skew
IPW User Command
Category - Image Transformation
NAME
skew - skew the lines of an IPW image
SYNOPSIS
skew [ -a angle ] [ -h ] [image]
DESCRIPTION
skew copies image (default: standard input) to the standard
output, skewing the origin of successive lines by a specified
angle.
OPTIONS
- -a angle
-
Introduce horizontal skew such the the left edge of the output
image is tilted "angle" degrees clockwise from vertical. The
resulting "dead space" in the output image is 0-filled. A
skew header is written to the output image.
If -a is not specified, then the skew indicated by the input skew
header is removed.
- -h
-
ignore input skew header. This allows an image to be skewed
more than once, e.g. during rotation by shearing.
- -h
-
may not be specified unless -a is also specified.
- -P nthreads
-
number of threads to use, default=1 (parallel processing)
OPERANDS
- [image]
- image
EXAMPLES
The command:
skew -a 30
causes the following transformation:
+-----------+ +---------------+
| | |000/ /|
| input | |00/ output /0|
| image | |0/ image /00|
| | |/ /000|
+-----------+ +---------------+
FILES
$WORKDIR/skewNNNNN
Temporary copy of all input headers.
DIAGNOSTICS
- image is already skewed
-a was specified, and the input image contains a "skew"
header.
- image is not skewed
-a was not specified, and the input image does not contain
a "skew" header.
- band band has no skew header
different skew angles: bands 0, band
If -a is not specified, then all input bands must have a
"skew" header, and they must be the same.
RESTRICTIONS
The skew angle given by -a must be between -45 and 45 degrees.
If -a is specified then the input image must NOT have a skew header,
unless -h is also specified, and a "skew" header is written to the
output image.
If -a is NOT specified then the input image must contain a "skew"
header with the same skew angle for all bands. The skew indicated
by this header is removed from the output image, and no "skew"
header is written to the output image.
HISTORY
- Jul 1990
-
Written by James Frew, UCSB.
Base IPW routine (Frew, 1990)
- Apr 1993
-
Converted to ANSI C, ran through Purify.
Dana Jacobsen, ERL-C.
- Nov 2015
-
Read in full image before transpose, parallel, allow skew.c to be called as a stand alone function. Scott Havens. USDA-ARS.
BUGS
None that we know of
SEE ALSO
- IPW
- flip,
gviewf,
horizon,
rotate,
transpose,
viewf
Frew, J., 1990. The Image Processing Workbench. Ph.D. Thesis,
Department of Geography, University of California, Santa
Barbara, CA, 382pp.
IPW documentation /
Last revised 9 November 2015 /
IPW web site