I ran a proximity (raster distance) function and I would like to invert the result.
Is there a simple way to do this without converting it back to vector format and editing the attribute table?
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Yes, raster calculator docs.qgis.org/2.2/en/docs/user_manual/working_with_raster/… the actual calculation depends on what you mean by invert.– Michael StimsonNov 22, 2017 at 1:05
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The proximity raster function creates pixels with higher values the further away from the object they are. I would like to invert those values so the numbers get smaller as they get further.– brinkNov 22, 2017 at 1:11
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4Use an n-R calculation where n is a constant and R is you cell value.. where R is small the output is large, where R is large the output is small.– Michael StimsonNov 22, 2017 at 1:15
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No worries! I'm glad you got a result. Can you please answer your own question, with screenshots preferably, for the benefit of users in the future who have the same requirement.– Michael StimsonNov 22, 2017 at 21:13
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2 Answers
Thanks to Mr. Stimson I used the expression 1000-(raster layer) to get the inverted raster result. I chose 1000 because it didn't have to be an exact invert and I didn't want negative numbers. I need to run it through r.cost algorithm which creates an error if there is a negative number. 
If you are wondering what number to use try this link How to extract pixel value counts from a raster in QGIS?
Invert values with QGIS Raster Calculator:
-1 * "yourRaster@1" + MAX("yourRaster@1")
but MAX() is not working properly according to some QGIS Bugs Reports.
Instead of MAX() put the maximum value of your raster. Then:
-1 * "yourRaster@1" + "put the maximum value of your raster"
Cheers
