Can’t stretch b&w image

[TrickyDicky]

I’m trying to black-clip (stretch) black&white image (as RGB) and on a real-time-preview it works, but as soon as I try to apply it to the image – nothing is happening to it, although the operation is registered (IMAGE – undo CurvesTransformation). Why?

[Carlos Milovic]

Try posting a screenshot to see what are you doing, and how your images/rtp looks like.

[TrickyDicky]

Here we are ..

[georg.viehoever]

Did you check if STF is active?

[Carlos Milovic]

Yes, it looks like there is an STF active. If the image is in the linear stage, then changing it with curves will show little or no impact (in this case, most values are gonna be clipped in the shadows). It is best to use CT in the non linear regime, after stretching.

[TrickyDicky]

NO, I didn't touch STF ...
As I said, putting the triangle on the image or clicking on the square does not affect the image, although the preview can be adjusted .. 

[Carlos Milovic]

Could you upload your image?
Maybe this is a bug...

[TrickyDicky]

Thanks Carlos,
here is the link:
http://www.freefilehosting.net/integrationcrop1rhtnotuc2adnrht

[NGC7789]

This is a jpeg and it looks like a mask. If what you meant by b&w is that there's only black or white pixels then there is nothing to stretch.

[TrickyDicky]

Thanks NGC...
Well, this is not a mask, it's a Ha image in a grayscale. All what I want to do is to b@#$!y black-clip it ..
What's funny,  when I reduce the image size to something like horizontal=12cm x 200px - it works - can this be explained?
 

[NGC7789]

That's my point. It doesn't look grayscale. It looks like a bitmap. Can you upload the original .fit?