[Processing] Rescale Raster gives bad results.

[roya0045]

The Rescale Raster tool gives nonsensical results in some instances.

I have a raster (float64) whose value are ranging from -1 to 255.

As those should represent a direction (originally from r.terraflow ) I want to turn them into quadrants.

When I process the data to rescale the values between 0 and 7 or 1 and 8.

In the resulting layer I seem to get an overflow and values are either between e-20 and 0 while some others are up in 7e+37

Tested on 3.16.1 and 3.16.3 ( the alg is inchanged so any change would be surprisig).

Works fine on raster with a positive range.

[gioman]

I have a raster (float64) whose value are ranging from -1 to 255.

@roya0045 can you attach it here?

[roya0045]

This should be sufficient. Data placement has been altered.
0-255_rast.zip
With the default values its somewhat fine, but for a small range, it breaks. The result should look checkered if you limit the values between -1 and the intended max value.

[roya0045]

With the normalisation formula in the raster calculator the output is fine.

[roya0045]

-1 as the minimum value seems to be the cause. I tried but offsetting the values by 1, it works fine, and with an offset or -3, making the minimum -4, its also fine.

[roya0045]

@gioman Did you had the chance to test and is the behavior the same on Linux?

[gioman]

@gioman Did you had the chance to test and is the behavior the same on Linux?

@roya0045 yes, is the same (master).

[roya0045]

Thank Gio!

@alexbruy simple ping to inform you of this issue.