Blend / combining several images

[markmarques]

Hi ...
I am seeking some advise on how can I blend or compose 4 or more images into one ...
Some details : the images have the same size but different brightness levels ...
In someway I am trying to make a combined HDR image in grayscale only ...
So common HDR software and ToneMapping is not needed ...

But after reading the image web Docs I still can not have figured out how to "blend it" or composite them correctly ...

For instance : how can I define in "blend" or compose or composite options that I only want to combine the 75% highest whites or the opposite ?

I can define an image with the the black| white threshold but it becomes too harsh ...
Anyone have tried something similar ?

[fmw42]

use a mask image with your other two images in the composite where the mask identifies the brightest 75% pixels. see http://www.imagemagick.org/Usage/compose/#compose

You will have to composite them two at a time with the appropriate mask for each.

[anthony]

For multiple image composition see... Layering Images.
http://www.imagemagick.org/Usage/layers/

Many different techniques, what you use depends on your input and desired results.