.ds Vn 1.12
.TH vrotate 1Vi "24 April 1993" "Vista Version \*(Vn"
.SH NAME
vrotate \- rotate an image
.SH SYNOPSIS
\fBvrotate\fR [\fB-angle \fIangle\fR] [\fB- \fIoption\fR ...] \
[\fIinfile\fR] [\fIoutfile\fR]
.SH DESCRIPTION
\fBvrotate\fP rotates each input image by the specified angle, producing a 
file of output images. The rotation is done by first rotating the image by 
a multiple of 90 degrees (using flips and transpositions) to an angle 
nearest to the specified angle, and then by completing the rotation using 
Alan Paeth's three-shear method. 
.PP 
Because each pixel in the rotated image is a weighted average of the 
corresponding pixels in the original image, the set of colors (or gray 
shades) used by the original image will not be preserved in the rotated 
image. 
.PP
In general, the edges of the rotated image will not be parallel to the 
vertical and horizontal axes. In such cases, the output image will be the 
smallest rectangular region containing the whole rotated image. Portions of 
the output image not covered by the rotated image will be filled with 
zeros. 
.SH "COMMAND LINE OPTIONS"
\fBvrotate\fP accepts the following options in any order:
.IP \fB-help\fP 15n
Prints a message describing options.
.IP "\fB-in\fP \fIinfile\fP"
Specifies a Vista data file containing the input images.
.IP "\fB-out\fP \fIoutfile\fP"
Specifies where to write the output images as a Vista data file.
.IP "\fB-angle\fP \fIangle\fP"
Specifies the angle of rotation in degrees. Positive values rotate 
counterclockwise; negative ones rotate clockwise. Default: 90.
.PP
Input and output files can be specified on the command line or allowed to
default to the standard input and output streams.
.SH "SEE ALSO"
.BR VImage (3Vi),
.BR Vista (7Vi)
.br
``A Fast Algorithm for General Raster Rotation'' by Alan Paeth,
\fIGraphics Interface '86\fP, pp. 77-81.
.SH AUTHOR
Daniel Ko <ko@cs.ubc.ca>