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: http://xmm.vilspa.esa.es/sas/6.5.0/doc/colimplot/node4.html
Дата изменения: Tue Aug 16 04:42:09 2005 Дата индексирования: Sat Dec 22 10:10:12 2007 Кодировка: Поисковые слова: trapezium |
This task is designed to produce colour plots, the displayed colour at any pixel being a function of the relative intensities in the supplied energy/wavelength bands. Although designed originally to display EPIC X-ray images, it can also be used to create false-colour plots from OM images. The assignment of colour attempts to mimic that of visible light, ie objects bright at long wavelengths are coloured red, those bright at short wavelengths, blue.
The task takes for its input any number of FITS images, each made in a different band of energy or wavelength. However at least 2 images are necessary for colour rendering. If the colour coding of x-ray hardness is to be preserved, the images should be listed on the command line in order of increasing energy or hardness (ie of decreasing wavelength for OM images).
The created colour image may either be stored in one of the file formats accessible via the pgplot library, or as a 3-plane fits file, or as a ppm image. The last format can be converted to gif or png by use of external (eg netpbm) utilities which bypass the 256-colour-name pgplot limitation on the number of colours available.
Processing of the input is divided into two broad sections: manipulations of the colour values of each pixel; and distributing the pixel colours among a much less numerous set (256 or even less) of pgplot-allowed colour indices.