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ZOOM_XY

ZOOM_XY

Name


      ZOOM_XY

Purpose


      Converts X, Y position on the image array to the the X,Y position
      in the current window. (These positions are identical
      only for an unroamed, zoomed image with with pixel [0,0] of the
      image placed at position [0,0] on the image display.)

Calling Sequence


      ZOOM_XY, Xim,Yim,Xtv,Ytv, [ OFFSET =, ZOOM = ]

Inputs


      XIM - Scalar or vector giving X position(s) in an image array.
      YIM - Like XTV but giving Y position(s) in an image array.
      If only 2 parameters are supplied then XIM and YIM will be modfied
      on output to contain the converted coordinates.

Optional Keyword Input


      OFFSET - 2 element vector giving the location of the image pixel (0,0)
              on the window display. OFFSET can be positive (e.g if the
              image is centered in a larger window) or negative (e.g. if the
              only the central region of an image much larger than the window
              is being displayed.
              Default value is [0,0], or no offset.
      ZOOM - Scalar specifying the magnification of the window with respect
              to the image variable.

Outputs


      XTV,YTV - REAL*4 X and Y coordinates on the image display corresponding
              to the input data coordinates.

Common Blocks


      If present, ZOOM_XY will use the TV and IMAGE common blocks which are
      defined in the MOUSSE software system (see
        http://archive.stsci.edu/uit/analysis.html) If the user is not using
      the MOUSSE software (which keeps track of the offset and zoom in each
      window) then the common blocks are ignored.

Notes


      The integer value of a pixel is assumed to refer to the *center*
      of a pixel.

Revison History


      Adapted from MOUSSE procedure of the same name W. Landsman HSTX Mar 1996
      Converted to IDL V5.0 W. Landsman September 1997
      Properly include ZOOM keyword W. Landsman May 2000
      Put back common blocks for MOUSSE compatibility September 2004



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