Starting the viewer

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7.1 Starting the viewer

Figure 7.1: The Viewer Display Panel (left) and Data Display Options (right) panels that appear when the viewer is called with the image cube from NGC5921 (viewer(’ngc5921.demo.cleanimg.image’)). The initial display is of the first channel of the cube.

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Within the casapy environment, the viewer task can be used to display an image or MS. The inputs are:

#  viewer :: View an image or visibility data set.

infile        =         ’’   #   (Optional)  Name of file to visualize.
displaytype   =   ’raster’   #   (Optional)  Type of visual rendering
                             #   (raster, contour, vector or marker).
                             #   lel  if an lel expression is given
                             #   for infile (advanced).

Examples of starting the viewer:

  CASA <1>: viewer()

  CASA <2>: viewer(’ngc5921.demo.ms’)

  CASA <3>: viewer(’ngc5921.demo.cleanimg.image’)

  CASA <5>: viewer(’ngc5921.demo.cleanimg.image’, ’contour’)

  CASA <5>: viewer(’"ngc5921.demo.cleanimg.image"^2’, ’lel’)

The first of these creates an empty Viewer Display Panel (§ 7.2.1) and a Load Data window (§ 7.2.4) . The second starts the viewer loaded with a Measurement Set. The third example starts the viewer with an image cube (see Figure 7.1).

Example four brings up a display panel as it was when its state was saved to the given ’restore’ file (ngc5921.usecase.clean.image.rstr). This includes the data displayed as well as options and viewer settings. (See § 7.2.2, Saving and Restoring Viewer State).

Examples five and six are less common cases, which make use of the second parameter (displaytype). Example five displays the image in contour form. Example six uses ’Lattice (Image) Expression Language’ to display the square of the image data.

NOTE: the viewer task determines file types (images, MSs, restore files) automatically. It is no longer necessary to specify filetype=’ms’ explicitly.

Figure 7.2: The Viewer Display Panel (left) and Data Display Options (right) panels that appear when the viewer is called with the NGC5921 Measurement Set (viewer(’ngc5921.demo.ms’)).

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7.1.1 Running the CASA viewer outside casapy

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