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AFFINE

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

NAME

affine - affine geometric transform

SYNTAX

affine [-ip n] [-bg <bg>] <inimage> <outimage> \
x0 x1 x2 y0 y1 y2
affine [-ip n] [-bg <bg>] -f <datafile> \
<inimage> <outimage>

DESCRIPTION

affine performs a linear transform of the coordinatesystem (x, y) to another coordinate system (u,v).All coordinates are adjusted acording to (xstart, ystart).
outimage (x,y) = inimage (u,v)
u = x0 + x1 * x + x2 * y
v = y0 + y1 * x + y2 * y

The interpolation method -ipis
-ip 0 : Nearest neighbor
-ip 1 : Bilinear   interpolation
         g(x) = bi(f(x), f(x+1), d)
         bi(x, y, d) = x(1-d) + yd
-ip 3 ; Cubic      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)))

The values x0 .. x2 and y0 .. y2 may be specified on thecommand line or in a datafile. The format on the datafile is
# Lines with # og ; in pos 1 is treated as comments
x0 x1 x2
y0 y1 y2

All matrix of size n x 2 (n >= 3) will be accepted.If n > 3 only element 0, 1, and 2 will be used.

Default is bilinear interpolation (-ip 1)

If the output image should have another size or startpointthan the input image this may be specified by the-xstart,-xstop,-xsize,-ystart,-ystopand -ysizeswitch. If start, stop as well as size switches are given, andinconsistently, the stop switch is ignored. The givensizes are clipped against the result of the transform.The -bgswitch is used to specify the value when themapping ends up outside the input. Default = 0.

RESTRICTIONS

inimagemust have bands with pixel type unsigned byte.

REFERENCE

Wayne Niblack. Digital Image Processing, p 131-150

AUTHOR

Otto Milvang

EXAMPLES

affine mona.img monarot.img 30 .5 .714 -40 -.0714 .5

ID

$Id: affine.c,v 1.32 1997/05/29 16:33:09 svein Exp $

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