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Daqarta for DOS
Data AcQuisition And Real-Time Analysis
Shareware for Legacy Systems

From the Daqarta for DOS Help system:



The CTRL-C color menu in spectrogram mode shows the colors for each of the 16 intensity weights, from highest at the top of the list to the lowest at the bottom. Note that the lowest color is always the same as the screen background.

Picking effective color sequences turns out to be very difficult, compounded by the fact that different monitors may have profoundly different color balances... and very few are user-adjustable in any orderly way, only as an incidental side-effect of contrast and brightness adjustments. This means that a good palette for one monitor may look bad on another... or bad on the same monitor after a contrast or brightness adjustment. Laptops pose a particular problem, since most have very poor color saturation.

To design a custom palette from scratch, set the monitor controls where they will hopefully stay, then decide on the color sequence... say, black to blue to violet to red. Set the bottom and top colors (black and red) and then guess where the middle colors (blue and violet) should fall. Set those colors as desired, then try splitting the gaps. For example, at the step midway between violet and red, set a color that is about equal proportions of each by eye. (The number values are not very good guides.) Then repeat for the other gaps, and move to still smaller gaps.

This whole process is much easier on a VGA system than on an EGA, since VGA primary proportions are adjustable in fine steps. For EGAs, you must pick a color sequence with a lot of colors in it, since there are less steps between colors. In general, a palette with fewer colors and finer steps looks better, but offers poorer actual value resolution because there is less contrast between steps.


While picking colors, you may want to spread or compress the colors in one part of the sequence. The following special operations apply only to the Spectrogram color menu:

    Moves the entire palette down from the cursor position, duplicating the color at that spot in the next lower, and losing the bottom color.
    Deletes the color at the cursor, moving the upper palette down and duplicating the top.
    Moves the entire palette up from the cursor, duplicating the next higher and losing the top.
    Deletes the color at the cursor, moving the lower palette up and duplicating the bottom.

The CTRL-INS and SHIFT-INS commands also assume that since the color at the cursor has been duplicated, it will need to be changed. That color item is thus selected for adjustment and the main cursor moved to the submenu.


Hit CTRL-PgDn while in the Spectrogram Color menu to roll to the special ColorMap menu. Hitting CTRL-PgDn again will get you back to the regular Spectrogram Color menu.

The ColorMap menu is needed because only 16 colors can appear on the screen at one time in this video mode, and all 16 are assigned as part of the color weight sequence for the Spectrogram. The other features of the screen like the menu cursor, axes, labels, and the menus themselves must thus be shown in colors chosen from the same 16 used as weights. The ColorMap menu allows you to make these assignments without affecting the color weights.


The top item in the ColorMap menu is the Palette, which is a mirror of the Palette item in the main Spectrogram menu. You can use this to select the palette you want to remap. Color Map assignments are stored along with each Spectrogram Palette, both in memory and for palettes saved to a file.


The Assign submenu below the Palette item shows a list of the four features that may be reassigned:

  • CURS
  • AXES


Below the Assign submenu is the Select submenu, which is a copy of the main Spectrogram color weight menu. When you move the cursor to a feature in the Assign submenu, a marker (*) will appear in the Select submenu corresponding to the color currently assigned to that feature. Move the cursor to the feature you want to change, and the Select marker will move correspondingly.

Now hit ENTER, and the cursor jumps down to the Select submenu where the marker was, and a marker is left in the Assign submenu to show which feature you are changing.

Move the cursor up or down in the Select submenu to the new color you wish to assign to the feature. As you move the cursor among the colors, the feature will take on the color at the current cursor position. When you find the color you want, hit ENTER. The cursor jumps back to that feature in the Assign submenu and is replaced with the marker at that location in Select.


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