register input output database transform
input
List of images to be transformed.
output
List of output images.
database
The name of the text file database produced by GEOMAP containing the coordinate
transformation(s).
transform
The list of the database record(s) containing the transformations.
The number of transforms must be 1 or the same as the number of input
images. Transform is usually the name of the
text file input to GEOMAP which lists the reference and input
coordinates of the control points.
geometry = geometric
The type of geometry to be applied: The choices are:
linear
The linear part, shifts, scales and rotations are computed.
geometric
The full transformation is computed.
xmin = INDEF, xmax = INDEF, ymin = INDEF, ymax = INDEF
The minimum and maximum x and y reference values of the output image.
Xmin, xmax, ymin and ymax default to minimum and maximum values set in GEOMAP,
and may not extend beyond the bounds of those parameters.
xscale = 1.0, yscale = 1.0
The output x and y scales in units of reference x and y
units per pixel, e.g "/ pixel or Angstroms / pixel if the reference
coordinates
are arc-seconds or Angstroms. If the reference coordinates are in pixels
then xscale and yscale should be 1.0 to preserve the scale of the reference
image. The default is set for pixel coordinates.
If xscale and yscale are undefined (INDEF), xscale and yscale default to the
range of the reference coordinates over the range in pixels.
Xscale and yscale overide the values of ncols and nlines.
ncols = INDEF, nlines = INDEF
The number of columns and lines in the output image. Ncols and nlines default
to the size of the input image. If xscale or yscale are defined ncols or nlines
are overidden.
xsample = 1.0, ysample = 1.0
The coordinate surface subsampling factor. The coordinate surfaces are
evaluated at every xsample-th pixel in x and every ysample-th pixel in y.
Transformed coordinates at intermediate pixel values are determined by
bilinear interpolation in the coordinate surfaces.
interpolant = linear
The choices are the following.
nearest
Nearest neighbour.
linear
Bilinear interpolation in x and y.
poly3
Third order polynomial in x and y.
poly5
Fifth order polynomial in x and y.
spline3
Bicubic spline.
boundary = nearest
The boundary extension choices are:
nearest
Use the value of the nearest boundary pixel.
constant
Use a constant value.
reflect
Generate value by reflecting about the boundary.
wrap
Generate a value by wrapping around to the opposite side of the image.
constant = 0.
The value of the constant for boundary extension.
fluxconserve = yes
Preserve the total image flux. The output pixel values are multiplied by
the Jacobian of the coordinate transformation.
nxblock = 256, nyblock = 256
If the dimensions of the output image are less than nxblock and nyblock
then the entire image is transformed at once. Otherwise blocks of size
nxblock by nyblock are transformed one at a time.
REGISTER corrects an image for geometric distortion using the coordinate transformation computed by GEOMAP. The transformation is stored as the coefficients of a polynomial surface in record transform, in the text file database. The coordinate surface is sampled at every xsample and ysample pixel in x and y. The transformed coordinates at intermediate pixel values are determined by bilinear interpolation in the coordinate surface. If xsample and ysample = 1, the coordinate surface is evaluted at every pixel. Use of xsample and ysample are strongly recommended for large images and high order coordinate surfaces in order to reduce the execution time.
Xmin, xmax, ymin and ymax define the range of reference coordinates represented in the output picture. These numbers default to the minimum and maximum x and y reference values used by GEOMAP, and may not exceed these values. The scale and size of the output picture is determined as follows.
ncols = ncols(input) if (xscale == INDEF) xscale = (xmax - xmin ) / (ncols - 1) else ncols = (xmax - xmin) / xscale + 1 nlines = nlines(input) if (yscale == INDEF) yscale = (ymax - ymin ) / (nlines - 1) else nlines = (ymax - ymin) / yscale + 1
The output image gray levels are determined by interpolating in the input image at the positions of the transformed output pixels. If the fluxconserve switch is set the output pixel values are multiplied by the Jacobian of the transformation. REGISTER uses the routines in the 2-D interpolation package.
If the environment variable nomwcs is "no" then the world coordinate system of the input image is modified in the output image to reflect the effects of the linear portion of the registration operation. Support does not yet exist in the IRAF world coordinate system interface for the higher order distortion corrections that REGISTER is capable of performing.
It requires approximately 70 and 290 cpu seconds to correct a 512 by 512 square image for geometric distortion using a low order coordinate surface and bilinear and biquintic interpolation respectively (Vax 11/750 far).
4 1.
Transform an image to the reference coordinate system. The output image
will have the same scale as the reference image if the reference
coordinates are in pixels.
cl> register input output database transform.le
cl> register input output database transform xscale=2.5 yscale=2.5.le
cl> register input output database transform xscale=2. yscale=2. >>> inter=spline3 flux-.le
cl> register im1,im2,im3 imout1,imout2,imout3 database >>> coord1,coord2,coords3.le
register @inlist @outlist database @reclist.le
Support does yet exist in the IRAF world coordinate system interface for the higher order distortion corrections that REGISTER is capable of performing.
imshift, magnify, rotate, imlintran, geotran, geomap,