set_gray — Define gray values for region output.
set_gray defines the gray values for region output. Gray values are defined as the range of the color lookup table that is used for gray value output with disp_image in conjunction with set_paint(::WindowHandle,'gray':). These entries can be modified by set_lut. So a 'gray value' is the color in which a pixel with the same value is displayed (not necessarily really gray). In general, when changing the color lookup table with set_lut, the colors of the displayed image will change too.
If a gray value is needed as a color for image output (i.e. no color changes with set_lut are possible), it can be set with set_color(::WindowHandle,'gray':).
If only a single gray value is passed, all output will take place in that gray value. If a tuple of gray values is passed, all output will take place in gray values modulo the number of tuple elements. In the example below, the first circle is displayed with gray value 100, the second with 200 and the third with 100 again. Every output operator starts with the first gray value. Note, that the number of output gray values depends on the number of objects that are displayed in one operator call. If only single objects are displayed, they always appear in the first gray value, even if the consist of more than one connected components.
When the operators set_gray, set_color, set_rgb, set_hsi are called, the overwrite the existing values. If not all gray values are displayable on the output device, the number range of GrayValues (0..255) is dithered to the range of displayable gray values. In any case 0 is displayed as black and 255 as white. The displayable gray values can be queried with the operator query_gray. With set_check(::'~color':) error messages can be suppressed if a gray value can't be displayed on the screen. In that case, a similar gray value is displayed.
Gray values for region output.
Default value: 255
Suggested values: 0, 1, 2, 10, 16, 32, 64, 100, 120, 128, 250, 251, 252, 253, 254, 255
Typical range of values: 0 ≤ GrayValues ≤ 255
set_hsi returns 2 (H_MSG_TRUE) if the window is valid and the given gray value is displayable. Otherwise an exception is raised.