[Radiance-general] 3.8 Falsecolor Scale

[Rob Guglielmetti]

On Nov 11, 2006, at 11:14 AM, Mark de la Fuente wrote:

> I find people understand the blue - red scale as well.  Since  
> falsecolor images are usually presented to clients, having "bloody"  
> pictures is often a very effective communication tool.  Probably  
> some psychological thing that dates back to hunting mammoths saber  
> tooth tigers!

I agree with the red=danger aspect; it's one of the things I like  
about the scale.  Blue is calming, red is alarming.  And another  
thing: clients freak out enough with the few colors we show them  
sometimes; adding more color to the mix may make things worse.  John,  
I can see where you are coming from (Greg too), and I think both  
scales have merits.  THanks Greg for adding the "-spec" option.

>
> I suppose in Radiance one could to a pextrem command on a picture  
> to get the maximum value and then use that to set the scale, but  
> having it spit out something like the following can be a little  
> intimidating.  :)
>
> 499 499 0.000000e+00 0.000000e+00 0.000000e+00
> 322 218 2.706250e+01 2.693750e+01 2.706250e+01
>
> I've tried to use this before, but have come up with numbers I  
> don't feel comfortable using.


Hmmm, what do you mean, you don't feel comfortable with these  
numbers?  I use pextrem all the time in conjunction with falsecolor.   
If you simply run 'pextrem -o' on a radiance image and multiply the  
green channel of the high pixel by 179, you have your maximum value  
for the -s option.


>
> Seems like a "-s max" setting would be useful.  Where setting the  
> scale to "max" would automatically check the image and set the  
> scale to the max pixel value automatically.

yeah, and this is probably easy for anyone who doesn't suck at  
programming, as I do.  I just spent longer than I care to share  
trying to add such an option to falsecolor.  It should be easy, but I  
couldn't sort out what values to use for certain variables.  Greg has  
already done a lot of the work, since the -e option already has code  
to run pextrem to find the max (and min) values and assign them to  
variables within the script (falsecolor is actually just a shell  
script).  But I don't know how the scale option gets applied to the  
legend.  (Greg, I can share with you what I have so far, if you wanna  
take it the rest of the way. )

- Rob