Re: [PyOpenGL-Users] False color images

[Nicolas R. <Nic...@in...>]

Have a look at glumpy. Colorization is done using a pixel shader and the colormap is stored in a 1D texture.

http://code.google.com/p/glumpy/



Nicolas


On Feb 11, 2012, at 0:43 , Gordon Wrigley wrote:

> I would think the normal approach would be to use a fragment shader to do a texture lookup, using your 16-bit colors brightness values as the texture coordinate. That would allow a totally arbitrary mapping between input brightness and output color.
> 
> On Sat, Feb 11, 2012 at 10:26 AM, Mike C. Fletcher <mcf...@vr...> wrote:
> On 12-02-10 05:33 PM, Derakon wrote:
> > I have a program that displays monochrome camera images, obtained as
> > Numpy arrays of 16-bit integer pixel brightnesses. I'd like to have a
> > false-color mode that displays low values as blue and high values as
> > red, to get some extra contrast and make it easier to tell where the
> > brightest pixels in the image are. I did some searching around and
> > about all I can find is some discussion on using color-index mode,
> > with concern that it's really meant for palettized sprites and isn't
> > really recommended these days. Is that accurate?
> >
> > Presumably this task has been done before; what's the recommended way
> > to do false color? Especially, I want to be able to rescale what value
> > is considered the darkest and what the brightest on the fly -- for
> > example, if I get an image where the distance between darkest and
> > brightest pixel is only 1000 (~10 bits) then I don't want to be
> > scaling things as if the brightest pixel is 2^16-1 and the darkest is
> > 0.
> >
> > Any advice would be recommended. Thanks.
> Why not simply do the scaling in the numpy array?  That is, to increase
> the dynamic range array = array - min( array); array = array *
> (2**16-1/max(array)) (sorry if I messed up the numbers there, hopefully
> you get the idea, I have a two year old yelling in my ear at the
> moment).  To do the false-color, you can use a shader, or just duplicate
> the data into RGB channels. Indexed-color mode is pretty poorly
> tested/supported these days; it may work, but I can't say I've used it
> in the last decade or so.
> 
> HTH,
> Mike
> 
> --
> ________________________________________________
>   Mike C. Fletcher
>   Designer, VR Plumber, Coder
>   http://www.vrplumber.com
>   http://blog.vrplumber.com
> 
> 
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