Re: [GM-help] Equivalent to IM's Fx operator? Or how to apply a color lookup table?

[Bob F. <bfr...@si...>]

On Wed, 30 Sep 2009, Evan Kaufman wrote:

> I'm porting some code that currently uses ImageMagick, and I was 
> wondering if GM has any equivalent to IM's Fx operator.
> 
> Specifically, I want to apply a mathematical formula to one image 
> using the data of another image.  The formula I used with 
> Imagemagick is "v.p{0,u*v.h}", which breaks down as follows:
> 
>     for each pixel in image u, multiply its channels by the height of image v.
>     this results in a height offset we'll call w.
>     the color at the given offset in image v (x=0, y=w) is then used for the current pixel in image u.

GraphicsMagick does not have anything like ImageMagick's Fx operator.

> The end result of this is to apply a color lookup table, and though 
> I notice that a -hald-clut option has been added in recent versions, 
> I'm wanting to support older versions of GM as well.  What would be 
> the best way to accomplish something like this?

Another way to apply a LUT is via an ICC ICM color profile (-profile 
option).  You can use a profile generator to create the profile (a 
file) and then use it to apply a LUT to the image.  Any GraphicsMagick 
which is linked with lcms supports -profile.

Bob
--
Bob Friesenhahn
bfr...@si..., http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/