I have a spectrogram of a sound

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Darker colors mean quieter parts, brighter colors - louder ones. I need to erase all "quiet" parts from an image and keep all "loud" ones. Loudest parts are represented by shades of yellow. I'm only interested in partly keeping the spots marked by white rectangles.

How do I erase everything that's not bright yellow from an image using Gimp?

P.S. Unfortunately, it's not an option for me to do it analyzing the actual sound. This needs to be done through analyzing the image.

1 Answer 1


You can use Colors > Components > Mono Mixer to convert other than yellow to black and yellow to white:

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You must decide how much orange can be accepted. In the next mix less orange has passed through:

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If it must be yellow you can colorize the image:

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