HOME GUIDE OPERATIONS DOCS ERRORS FORMATS INSTALL NEW TIPS WEB SITES

SH F - SHift - using Fourier interpolation

(09/03/96)

PURPOSE

Shifts a picture or a volume by a specified vector.

SEE ALSO

SH [Shift using bilinear interpolation]

USAGE

.OPERATION: SH F

.INPUT1 FILE: PIC001
[Enter the name of the picture to be shifted.]

.OUTPUT FILE: SHI001
[Enter the name of the file where the shifted picture is to be kept.]

.SHIFT COMPONENTS IN X-Y: -5.2,6.5
[Enter the shift vector components.]

[In the above example, PIC001 will then be shifted by -5.2 units in the x direction and 6.5 units in the y direction, and the result will be written into SHI001.]

If input is 3D, the system asks an additional question:

.SHIFT COMPONENT IN Z: 2.2

NOTES

  1. The shift parameters can be specified by reference to the temporary register: -X11,-X12, will input the components (with inverted sign) of a shift vector found in a previous 'CC' and 'PK X11,X12' operation. Whether or not the sign has to be inverted follows from the order of argument files in the 'CC' operation.

  2. DNEW (K,I) = DOLD (K',I')
    where K' = K + KSH, I' = I + ISH
    Note that the shift is circular, i.e., the image is repeated in all directions. The effective new coordinate pair is:
    K' = MOD (K + KSH, NSAM)
    I' = MOD (I + ISH, NROW)
    Because of the use of the circular shift, SH F has the effect of multiplying the Fourier transform with:
    exp (2 [pi] j (KSH * KX/NSAM + ISH * KY/NROW))

SUBROUTINES

SHIFT_PF, SHIFT_3D

CALLER

UTIL2

© Copyright Notice /       Enquiries: spider@wadsworth.org