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Using ximtool

  The IRAF image display window is ``ximtool", and combines the best features of Sunview/IMTOOL with SAOIMAGE. To load an image into the display, simply type display image 1, where the ``1" denotes display frame number 1. (Up to 4 images can be loaded in frames 1-4.) This command uses many defaults that sometimes need to be changed, depending on the data and your needs.

Since ``ximtool" contains a ``panner box", how we recommend using the display is a little different than what we described in previous versions of this manual for Sunview/IMTOOL.

Since the largest image that physically fits on the screen contains only about 1000 pixels on a side, and since many of our CCDs are considerably bigger than this, there is some trickiness to how you might want to display your data. Basically you have two options:

  1. Set the buffer size ( set stdimage=imtname) to the full size of the image, and display to it using display imagename 1 fill-. The fill- will assure that each pixel in the image gets mapped into a single pixel in the display. For our large chips, however, only a subsection of the image will fit on the displayed area. Fortunately there is a panner box in the upper right hand corner of the window which will show you the entire image with a bright green box indicating which subregion is displayed on the main part of the window. The advantage of this is that when you see a pixel, it is really a pixel, and you can easily evaluate things like bad pixels and columns. The disadvantage is that you cannot see the entire image at once, but must move the panner box in order to change the region being shown.

  2. Set the buffer size ( set stdimage=imtname) to something small enough to fit on the screen but display to it using display imagename 1 fill+. The fill+ means that every pixel in the image will contribute to the intensity of each pixel in the display, but not 1:1. In other words, if you were displaying a 1024 x 1024 image into a frame buffer that was 512 x 512 large, using fill+ would be the same as averaging adjacent pixels. The advantage of this is that you will see the entire frame without having to move the panner box; the disadvantage will be that even if you ``zoom", you will not be seeing actual individual pixels.

Note: In the past we recommended using the ``fitframe" option. However, if you do this with an frame buffer larger than the frame size, you are in danger of ``losing" your window---you may not be able to reach the control bar to have any effect on the window!

The first author on this document prefers option (1) for spectroscopic applications but (2) for direct imaging. One of the other authors prefers to do both, using (2) [see the full frame] in the ``Data Acquisition" window, so that images will be automatically displayed showing the full field, but then setting the defaults in the ``Data Reduction" window using (1) so that each pixel can be cherished by redisplaying an image from there.

By default, obsinit sets the frame buffer to a small size () for t2ka, t2kb, and s2ka, but uses the full size for chips used solely for spectroscopic applications (gcam, cryo).

A complete list of frame buffers is available by typing the command gdevices.

Once the image is loaded, you can adjust the brightness and contrast parameters by moving the mouse in the window while holding down the right-hand button. Negative contrast (black stars on white background) is realized by moving the mouse to the upper half of the ximtool window; positive contrast is obtained by moving the mouse to the lower half of the window. Higher contrast is achieved by moving the mouse vertically away from the center. The image is made darker (blacker) by moving the mouse to the upper left (negative contrast) or lower right (positive contrast). The most extreme displays are usually obtained when the mouse is in one of these two corners.

You can learn the approximate pixel location of the mouse by reading the value in the box at lower right. The intensity is also displayed there. If the intensity read-out has a ``+" or ``-" next to it, the pixel is either brighter or fainter than the display command has scaled the data. To change the scaling from the default, use the display command as follows:

display image 1 zscale- zrange- z1=0 z2=2000

to set the scaling is now set to 0-2000 rather than the automatic scaling printed out previously when display was executed.

You may also zoom the picture using the middle mouse button. Press the button once and the image will move in an attempt to center up on the mouse cursor. Press it again without moving the cursor and the image will zoom up a factor of 2. Pressing the middle button 3 more times will zoom the picture up to a factor of 4, 8, and back to 1 (normal). If you move the cursor while zoomed and then press the middle button, the picture will pan to center up on the cursor.

You can also pan by simply grabbing the green outline in the panner box using the left mouse button, and moving it to outline the part of the image you would like.

The controls on the upper right allow one to flip the image left and right, up or down, change frames (the frame number is displayed between the two fat arrows), and, best of all, open a control panel (left most icon). The control panel allows you to turn the coordinates box and panners on and off, flip, blink, and much, much more.

If you find that you have somehow mysteriously added little green boxes on your image, you can get rid of these by placing the cursor in such an extraneous box, holding down the right-most mouse button, and selecting ``Destroy".

next previous contents
Next: Using imexamine Previous: IRAF Networking
Updated: 26Aug1996