Keywords: greg

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### Bitmap Color Editing

GREG offers the possibility of editing the color look-up table (LUT) for bitmaps. The colors are represented by three SIC variables:

- `HUE`
  The `HUE` array, with values between 0 and 360, represent the color on a standard color cycle (from Red to Yellow, Green, Blue, Violet and Red again).
- `SATURATION` The `SATURATION` array, with values between 0 and 1, indicates the fraction of the original (saturated) color mixed with white. 0 is pure white, 1 a purely saturated color.
- `VALUE` The `VALUE` array, with values between 0 and 1, indicates the intensity. 0 is black, 1 is maximum lightness.

These variable can be modified by any standard SIC expression. The new values get transferred to the display by typing the command `LUT`. This command also accepts other arguments:

- `COLOR` Load a default color table
- `WHITE` Load a black and white color table (White background, black sources)
- `BLACK` Load a black and white color table (Black background, white sources).
- `LUT` Load the color table defined by the arrays. Same as without any argument.
- `EDIT` Calls an interactive look-up table editor (on X-Window systems onlyt) not yet implemented.
- `Any other` Red Green Blue values are read from the formatted file specified as argument. The RGB representation is converted to HSV before being used.

The color associated with the blanking value can be modified using the `B_HUE, B_SATURATION` and `B_VALUE` scalar variables.

Next: Pen Colors Up: Greyscale and Color plots Previous: Filled Areas Contents Index