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Appendix D
Appendix: CASA Region File Format

The CASA region file format provides a flexible, easily edited set of region definitions which are accepted across CASA tasks. Region files may be written by hand or using the CASA viewer.

Alert: Whereas the region format is supported by all the data processing tasks, the viewer implementation is still limited to rectangles, ellipses, and some markers.

For a file to be recognized as a valid CASA region text file, the first line must contain the string:

#CRTF

”CRTF” stands for ”CASA Region Text Format”. One may also include an optional version number at the end of the string, so it reads #CRTFv0; this indicates the version of the format definition.

Region files have two different kinds of definitions, ”regions” and ”annotations”, each of which is one line long. To indicate an annotation, a line must begin with "ann". Lines that begin with the comment character (#) are not considered for processing or display.

The second line of a file may define global parameters that are to be used for all regions and annotations in that file, in which case the line starts with the word "global". The parameters set here may also be overridden by keywords in a specific line, in which case the keywords pertain only to that one line.

• Regions: all regions are considered by tasks. They will be displayed by visualization tasks as well as used to create masks, etc., as appropriate.
• Annotations: these are used by display tasks, and are for visual reference only.

More information about CASA may be found at the CASA web page

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