[Radiance-general] Removing black areas in imagemapping

[Lars O. Grobe]

Hi!
> Also use phisto on your falsecolor image to see the
> actual values of the black pixels. It looks like there
> is a range of "dark grey" instead of black. If you convert
> your image to tiff or ppm, edit the grey values to black
> in Photoshop and convert it back you might have a
> better result already. I'm sure there is also a way to
> do this with Radiance tools but I don't have one ready.

I'd use pcomb:

pcomb -e 't=0.05; c=(.265074126*ri(1) + .670114631*gi(1) + 
.064811243*bi(1))-t; ro=if( c, ri(1), 0); go=if( c, gi(1), 0); bo=if( c, 
bi(1), 0);' -o image.hdr | ximage

In this example, t is the treshold (you have to adjust this) and 
image.hdr is the input. c is the condition, if the grey value of a pixel 
is > t, the input pixel is written, else rgb(0,0,0). There are even 
slightly simpler ways to do it, still pcomb -e is the generic way for me 
to calculate on images.

Cheers, Lars.