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ROTATE

Section: User Commands (1)
Updated: 16 Mar 1998
Index

NAME

rotate - rotate an image

SYNTAX

rotate [-ip n] [-bg <bg>] <inimage> <outimage> [-deg]
<theta> <rx> <ry>

DESCRIPTION

rotate an image around global coordinates (rx, ry).

The input image is rotated around the point (rx, ry) in theglobal coordinate system. Thus, an image of size 25x25 withxstart=ystart=100 should have rx=ry=112 to be rotated aroundits center. If xstart=ystart=1, global coordinates equal localcoordinates.

RESTRICTIONS

inimagemust have bands with pixel type unsigned byte.

OPTIONS

-deg

thetais specified in degrees, default: radians.
outimage (x,y) = inimage (u,v)
u = cos(theta) *  x - sin(theta) *  y
   - cos(theta) * rx + sin(theta) * ry + rx
v = sin(theta) *  x + cos(theta) *  y
   - sin(theta) * rx - cos(theta) * ry + ry

-ip n

The interpolation method, where nis one of

0Nearest neighbor

1Bilinear interpolation. This is the default.
g(x) = bi(f(x), f(x+1), d)
bi(x, y, d) = x(1-d) + yd

3Cubic interpolation
     g(x) = cc(f(x-1), f(x), f(x+1), f(x+2), d)
     cc(x, y, z, v, d) = y + d((-x+z) +
                 d((2x-2y+z-v) + d(-x+y-z+v)))

-bg bg

Specifies the background pixel value, default = 0.

REFERENCE

Wayne Niblack. Digital Image Processing, p 131-150.

AUTHOR

Otto Milvang

EXAMPLES

rotate mona.img monarot.img -deg 30 256 256

ID

$Id: rotate.c,v 1.30 1997/06/03 13:49:51 svein Exp $

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