IRAF and the CL

Using Images


This section will primarily be of interest to WF/PC and FOC observers, it explains:

Displaying Images

To display an image, you need to:

  1. Start SAOimage in a separate window from your IRAF session (i.e., either from a different xterm window, or as a background job before starting IRAF).

  2. Display the image using the IRAF display task.

Figure 2.8 shows how to display the standard IRAF dev$pix image.



Displaying an Image

Once the image appears in your SAOimage screen, you can use the SAOimage commands to manipulate or print your image.

Printing Images

The "print" button on the "etc" menu in SAOimage will print the visible display to a PostScript printer. You may optionally save the captured screen to a PostScript file by reconfiguring the SAOimage environment before starting it. (See the SAOimage User's Guide for instructions.)

Any displayed window may be saved as a raster image using one of several host (i.e., non-IRAF) tools. These tools include:

Perhaps the most universally useful format for printing or importing images into documents is PostScript. The xv program provides a very nice way to save images in PostScript. In addition, the PBM+ suite of programs include the ability to write PostScript, among other formats.

Non-PostScript printers require various image formats to print continuous-tone images. Usually, there is a specific tool that will format images appropriately for a given printer. For example, the EasyCopy/X (ecx) program reformats images from Sun rasterfile format to the format used by Mitsubishi Shinko color printers. (See "Shinko Thermal Color Printer" on page 26 of the STScI Site Guide for IRAF and STSDAS).

Image Sections and Groups

HST images are stored in a format called GEIS format, which actually consists of one or more related images, each in a separate group. You can work with the groups individually by simply enclosing the group number in square brackets. For example, in Figure 2.9, we show only group 2 of a WF/PC image.


If you do not specify a group, most tasks will operate on only the first group in the image.


You can also work with only part of the total image by specifying a pixel range, also enclosed in square brackets. The range is the starting point and ending point, with a colon separating the two. The X (horizontal) axis is specified first, then the Y (vertical) axis, separated by a comma. For example, specify group 3 of an image as: image.hhh[3]. You could specify a pixel range from 101 to 200 in the X direction and all pixels in the Y direction as: image.hhh[101:200,*]


If you use both group and image section syntax together, the group number must come first.




Displaying Sections and Groups of an Image

Tools for Working with Images

Both IRAF and STSDAS contain a large number of tasks that work with images. Some of the packages that you should investigate are:

Displaying Images
Printing Images
Image Sections and Groups
Tools for Working with Images

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