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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. Nov 22, 2017 at 1:05
  • 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.
    – brink
    Nov 22, 2017 at 1:11
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    Use 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. Nov 22, 2017 at 1:15
  • 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. Nov 22, 2017 at 21:13

2 Answers 2

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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. enter image description here

If you are wondering what number to use try this link How to extract pixel value counts from a raster in QGIS?

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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

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