[Gimp-user] from color range (blue to red) to greyscale range (white to black)

[rich404 <forums gimpusers com>]

> Hello,
>
> I hope you can help me with this issue since I could not find an
> apropriate solution so far. For my report I am not allowed to use
> diagrams with colors which are not recognisable after a black/white
> copy anymore, like the one attached to this message.
> Since a normal greyscale of the attached plot makes blue (lowest
> value) and red (highes value) looking similar. This is not an option.
> I am seeking for a quick way to, let's say translate from a color
> range (blue to red) to a grey scale (white to black). Since I have to
> do this for several images I would appreciate a quick way, if there is
> one...
>
> I heard that there are more than one weighting algorithms like
> (R+G+B)/2 or 0,3*R+0,7*B+0,11*G and so on, but basically I would be
> interested in 0*Blue + maybe 30*Green + 70*Red to achieve White as a
> minimum (which is now marked with blue color) and black as a maximum
> (which is now marked with red).
>
> Thank you in anticipation.
>
> Best regards.

A possibility to try.

I know how it can be done. Use a Look-Up-Table (LUT) to replace one colour with
another. Problem is I can not find a ready-made LUT.

There is a Gimp plugin gmic-gimp-qt (note the qt version) that lets you assemble
a bespoke LUT see: www.gmic.eu for download and instructions.

Very tedious to set up: looks like this: https://i.imgur.com/DNM2PDK.jpg

However once done, the settings can be saved. Those settings can also be
incorporated into a script (attached), which runs the gmic-gimp-qt plugin.

Unzip, pop in your gimp scripts folder. Find it bottom of the Filters menu along
with gmic.

Produces this:  https://i.imgur.com/I79QxDS.jpg the plugin has lots of work to
do, so be patient, it gets there.

Note it is still RGB and needs converting to greyscale Image -> Mode ->
Greyscale

rich: www.gimp-forum.net

Attachments:
* http://www.gimpusers.com/system/attachments/856/original/gmic_shell.zip

-- 
rich404 (via www.gimpusers.com/forums)