vbilinco(1)

PROGRAM
vbilinco - Compute bilinear geometric warp coefficients

SYNTAX

vbilinco

-i1 Source tie point image

-i2 Target tie point image

-o1 X vwarp coefficients image

-o2 Y vwarp coefficients image

[-o3]
    Tiepoint Error Image

[-V]
    Gives the version for vbilinco

[-U]
    Gives the usage for vbilinco

[-P]
    Prompts for command line options

[-A [file1]]
    Creates the answer file called vbilinco.ans or file1

[-a [file1]]
    Uses vbilinco.ans or file1 as the answer file

DESCRIPTION
vbilinco is used to compute the coefficients for the two bilinear equations that are commonly used to perform image registration for simple spatial distortion functions. The input images are really files of coordinates. Each input image should be of size N rows by 2 columns, of type FLOAT. There should be at least 4 tiepoints. If more than 4 tiepoints are supplied then a least squares fit is done. The coordinates are stored as N pairs of numbers. For example (x0,y0) (x1,y1) (x2,y2) (x3,y3) is stored as an array of floats as follows:
     x0 y0
     x1 y1
     x2 y2
     x3 y3 which is exactly how vprdata(1) should print out your coordinate file if it is in the right order. The first input file contains the coordinates of the tie points in the original (source) image. The second input file contains the desired coordinates of the tie points in the corrected (target) image.

The output files contain the coefficients for the two bilinear transforms:
     x' = a + b*x + c*x*y + d*y
     y' = e + f*x + g*x*y + h*y where the point (x,y) is mapped to (x',y') by the transform. The coefficients are stored in the output image as four floats (2 rows by 2 columns), in the order
     a b
     d c for the first image and
     e f
     h g for the second image.

The output image can be supplied directly to vwarp to perform the geometric correction.

The optional tiepoint error output image contains pairs of errors defined by (x'-x^),(y'-y^) where x^ is the approximation that the bilinear function gives to the position of x' by position x. This is a float image, with N rows and 2 columns, with each row corresponding to the tiepoint in that same position.

REQUIRED ARGUMENTS

-i1 type: infile
    desc: Source tie point image

-i2 type: infile
    desc: Target tie point image

-o1 type: outfile
    desc: X vwarp coefficients image

-o2 type: outfile
    desc: Y vwarp coefficients image

OPTIONAL ARGUMENTS

-o3 type: outfile
    desc: Tiepoint Error Image

EXAMPLES
vbilinco -i1 src_tie.xv -i2 targ_tie.xv -o1 Xcoeffs.xv -o2 Ycoeffs.xv

computes the bilinear warp coefficients required to transform the input tiepoints specified into the specified target positions.

SEE ALSO
intro(1), verror(3), vgparms(3), vutils(3), lvbilinco(3) vwarp(1), vpolyco(1)

RESTRICTIONS
vbilinco will only operate on VFF_TYP_FLOAT.

COPYRIGHT
Copyright 1991, University of New Mexico. All rights reserved.