Keywords: greg

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### Devices and Hardcopies

The color facilities are available only under X-Window systems. Moreover, not all X-Window like devices recognized by GREG effectively use the color for bitmaps. Only the `DEVICE IMAGE` does. This restriction exists because the color map allocate by GREG is a private color map. As a consequence, no more than a single GREG with `DEVICE IMAGE` can operate at any one time on an X-Window terminal. The pencil colors (pencils from 8 to 23) can always be edited. The number of bitmap colors is usually 128, but can be less if many color applications already use most of the available colors of the X-Window terminal.

For hardcopies, color is supported only the PostScript format. Two options exists for the type of PostSsript created: `GREY` or `COLOR`. The `GREY` version, used by `HARDCOPY /DEVICE PS GREY`, has a fixed transfer function of greyscales. The transfer function is non-linear, and reasonably suited for most astronomical images. The `LUT` command has absolutely no influence on this type of HARDCOPY. The `COLOR` version, used by `HARDCOPY /DEVICE PS COLOR`, uses the current `LUT` to produce the PostScript output. On Greyscale printers, the colors are converted to grey intensities using standard formulas (what you would see by replacing a color display by a monochrome one). Colors are used on color printers.

Next: Plot Architecture and Multi-Window Up: Greyscale and Color plots Previous: Pen Colors Contents Index