cut some values

[djibb]

Hi all,
i world like to 'cut', i.e. put to 0 some values above a treshold value.

Something like : if pixel value > 130 -> 0


The idea is to make some astronomical masks to remove noise. (erase signa, then substract noise)

How do I do this ? From scripts ?

[tmanni]

You can do this with the Threshold filter:
Ensure your image is 8bit integer (menu Image -> Precision)
then menu Colors -> Threshold...

• set the left input to 0
  
• set the right input to 130
  
• in Blending Options, set the Mode to Multiply