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Thank you. I think you are right. But I think this ACTC is meant for blobs and not "Truecolor" format.

But for "Truecolor" format using the matrix [0 0 0; 0.2 0 0; 0.4 0 0; 0.6 0 0; 0.8 0 0; 1 0 0] (and playing with it)

is more sensible.

 

Thank you.

Sincerely,

Abhinay D. Joshi
 

On 12/5/06, Ged Ridgway <[log in to unmask]> wrote:

Abhinay Joshi wrote:
> Could anyone please help me understand the term 'ACTC' which is
> colormap? what's does it excatly mean?

See "doc colormap" in Matlab. Basically, colormaps decide how values
(such as t-values, MRI intensities, segmentation probabilities, etc.)
show up on your screen.

The most common Matlab colormaps are jet (a kind of blueish-redish
spectrum, which gets its name from being originally developed for
fluid flow/jet visualisation; and its popularity from making dull
images look exciting ;-) ) and grey (higher values are brighter shades).

actc appears to be Matthew Brett's "activation" colormap, see:

http://imaging.mrc-cbu.cam.ac.uk/imaging/DisplaySlices
and
[log in to unmask]"> http:[log in to unmask]

as you can see from the first link, actc is a kind of blueish-redish
spectrum, probably developed with the same goal as jet (!)

Personally, I don't like these exciting all-around-the-spectrum
colormaps (which have slightly blueish-green and slightly
reddish-yellow looking kind of similar(ish), but on different sides of
zero). I would prefer a simpler straight line through the colour
wheel, like cyan-black-red, but with so many list subscribers studying
perception/vision/psychology I wouldn't dare to claim that this would
look perceptually better...

Yours,
Ged.

P.S. It's lucky SPM5 is so slow, otherwise I'd never have time to
write all this... (just kidding)