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SA - Sum Alignment

(3/27/96)

PURPOSE

To perform vector addition of rotation and shift values from two successive cycles of alignment of an image series. The summed values, saved in registers, can then be applied to the original images. Additive interpolation errors are thus avoided.

SEE ALSO

SA P [Sum alignment - positive rotation and shift]

USAGE

.OPERATION: SA X10,X11,X12,X20,X21,X22,X30,X31,X32

[The first three (input) registers specified contain the rotation angle, the x-shift value, and the y-shift value from the initial alignment cycle. The second group of three (input) registers contain the rotation and x and y shift values from the refinement cycle.

The first three will typically have been retrieved from a document file by an UNSAVE ('UD') operation just prior to the call to 'SA'. The second three can also have been UNSAVEd in this manner from another document file, or, if the 'SA' is performed in the same session (batch run) as the second cycle, they may simply be the current register contents (see below).

The final three registers specified are output registers, and receive the vector sums for the rotation and shift.

NOTES

  1. Rotational matrix used in SA has form:
    c -s
    s c
    It works for the angles and shifts obtained from CC IC and OR commands which have to be used with reversed signes in 'RT SQ'.

  2. 'SA' may be applied most conveniently within the second cycle loop. The intermediate image series (rotated and translated by the amounts found in the first cycle) are realigned against a refined reference, and the values are stored in X20-X22. The values from cycle 1 are then UNSAVEd into X10-X12, and 'SA' is used to obtain X30-X32. These output values are finally applied to rotate and shift the unaligned original image series. They should also be saved in another document file, using 'SD'. Note that two input and one output series must be on disk at one time. The original images may be deleted individually (within the DO-loop) once the corresponding final, aligned images have been obtained.

  3. After having obtained resulting angle and shifts the 'RT SQ' command is highly recommended for the final step.

SUBROUTINES

SUMALI

CALLER

DRIV1

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