The ZOOM procedure displays part of an image from the current window enlarged in a new ("zoom") window. The cursor is used to mark the center of the zoom area, and different zoom factors can be specified interactively.

This routine is written in the IDL language. Its source code can be found in the file zoom.pro in the lib subdirectory of the IDL distribution.

Using ZOOM

After calling ZOOM, place the mouse cursor over an image in an IDL graphics window. Click the left mouse button to display a magnified version of the image in a new window. The zoomed image is centered around the pixel selected in the original window. Click the middle mouse button to display a menu of zoom factors. Click the right mouse button to exit the procedure.

Using ZOOM with Draw Widgets

Note that the ZOOM procedure is only for use with IDL graphics windows. It should not be used with draw widgets. To obtain a zooming effect in a draw widget, use the CW_ZOOM function.

Calling Sequence




Set this keyword to make the zoom window track the mouse without requiring the user to press the left mouse button. This feature only works well on fast computers.


Use this keyword to specify the zoom factor, which must be an integer. The default zoom factor is 4.


Set this keyword to use bilinear interpolation. The default is to use pixel replication.


Set this keyword to keep the zoom window after exiting the procedure.


Normally, if ZOOM is called with KEEP and then called again, it will use the same window to display the new zoomed image. Set the NEW_WINDOW keyword to force ZOOM to create a new window for this purpose.


Use this keyword to specify the X size of the zoom window. The default is 512.


Use this keyword to specify the Y size of the zoom window. The default is 512.


Set this keyword to a named variable that will contain the index of the zoom window. KEEP must also be set. If KEEP is not set, ZOOM_WINDOW will contain the integer -1.

See Also