Re: ITT algorithm

[Klaus Banse <kbanse@eso.org>]

Sebastian Jester wrote:
> Hi,
>
>  can someone describe, or point me to a description of, the exact
> algorithm
> used in in applying intensity transfer tables (ITTs) to image data? I
> read the
> Midas documentation, but I would like to see some equations which I
> couldn't
> find.
>
> Thanks,
>
> Sebastian Jester
>
>
>

An ITT is simply a 1-dim table mapping an integer interval
[0,n-1] -> [0,n-1],
where n is the size of the LUT, e.g. 256 for 8-bit displays.

Image pixels (float or int) are scaled and mapped to an element
in the interval [0,n-1], say k,
and then this k is used as index into the LUT to get
the red, green and blue value to be sent to the display.
For pseudocolour mode you have a single index k for all
3 colours, for true colour you have 3 indices kr, kg and kb.

With an ITT enabled not the index k but the value m with
m = ITT[k] serves as index into the LUT.

Good luck,
Klaus