Data Translation DT3155, User Manual

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Chapter 2
22
Passthru LUT
It is assumed that the data passed to display memory is 8 bits/pixel.
By default, passthru operations load the Windows system palette
with 128 grayscale RGB values for display and use the default
passthru LUT of 256 monotonically increasing grayscales.
Using software, you can modify the 256-position passthru LUT so
that false coloring is used. For each entry in the passthru LUT, the
index of the closest matching RGB value in the Windows system
palette is used. If an exact match is needed, you can use software to
define 15 extra entries in the Windows system palette.
Overlays
If your system provides Direct Draw Interface (DDI) support, you can
add overlays to bitmap passthru operations. An overlay is an image
that you place on top of the image that was captured using passthru.
You cannot use overlays with direct passthru because they are
equivalent to an obstruction and cause passthru to pause.