There are two programmes, khuei
and
kvis
, that allow you to display
different images on top of each other, while each image has a
different colour coding. This can be used to display amplitude and
phase together in one image, or compare different channels from a data
cube by superimposing them.
These visualisation techniques require a 24-bit display.
khuei
is quite user-friendly, allowing
you to load two images of the same width and height. You can even load
one image in FITS format and the other in Miriad or GIPSY format. A menu allows you to combine the two images in several
ways.
Note that there is another way to superimpose images which involves
drawing one image as a greyscale or false-colour image and the other
is drawn over the top as contours. This can be done with
kvis
, and does not require a 24-bit
display.
You may also use the
send-contours
programme to
draw contours over any image. This programme is a command-line tool,
however, and is not normally used since the the GUI tools are much
easier to use.
With the program khuei
you can superimpose two images,
where one image is taken to control the intensity and the other the
colour. This can be used to display amplitude and phase together in
one image, or line integral and a velocity field.
To display the images run
khuei
First load File1 and File2. You should now see the combined images. The sliders Start Hue and Stop Hue manipulate the colour of the image, the sliders Minimum Intensity and Saturation the intensity.
By default, File1 will control the intensity, and File2 the hue. You can swap this by choosing ``Phase, Amplitude'' from the RAW DATA FORM menu. If you select ``Real, Imaginary'' then a rectangular to polar transformation of the data is performed, where File1 is real image and File2 is the imaginary image. You can swap the sense of this by choosing ``Imaginary, Real''. After the rectangular to polar transformation, the amplitude value will control the intensity and the phase value will control the hue.
A screen snapshot is available here
Another possibility is to overlay images so that all images are coded
as intensity but in a different colour. This you can use to overlay
two or three different channels of a data cube and inspect subtle
differences. The kvis
programme can be
used to do this.