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#### A.10.1.5 Display Image

Configuration for Display Image action

The Display Image action uses the contents of a column to provide a URL or filename giving the location of an image to display in an internal viewer. The image can be in a graphics format such as JPEG, PNG, or GIF, or it can be a FITS image. The standard image support is implemented by Java's ImageIO library, so the details of installation determine what formats are supported. Java version 9 has more extensive image format support than earlier Java versions.

Note that for more sophisticated image handling, especially for FITS images, the Send FITS Image option in conjunction with an external image viewer application may be more appropriate.

Configuration:

Image Location
  Gives the URL or filename of the image to display for each row. A column name may be selected from the drop-down list, or the expression language may be used to assemble a location string from other columns.
Image Viewer
  Selects which of the internal image viewers will be used for display. At least some of the following options will be available; see Appendix A.10.2 for more detail:
  - Basic: A minimal image viewer.
  - Basic (allow preprocessing): The same image viewer as Basic, but the image location is permitted to contain a preprocessing system command, for instance "`< convert " + filename + " -normalize png:-`", using the ImageMagick `convert` command. This rather advanced usage may only work on Un*x-like OSs. This option is usually not required, and has security implications; if it is used in an action loaded from a session file, the security panel will be displayed.
  - SoG: The SoG image viewer provides more faciliites including zoom, colour map manipulation etc. It may or may not be available depending on how TOPCAT is installed

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk