Re: masking in rio calc

Sean Gillies

Hi Matt,

On Tue, Nov 17, 2020 at 5:57 PM Gregory, Matthew <matt.gregory@...> wrote:
Hi all,

I'm wondering if I'm using rio-calc incorrectly to achieve what I'd like to do.  I have a floating-point raster that ranges from 0.0-1.0 with areas in the raster that are masked.  I'd like to simply create a 0|1 threshold raster based on 0.5 as a threshold value *and* retain the mask which I'd like to set to 255 in a uint8 output.  My command is:

  rio calc
    -f GTiff
    -t uint8
    --profile nodata=255
    "(>= (read 1) 0.5)"

When I run this, I believe the ">=" in the expression gives me a np.bool type which then gets filled here ( before being cast to the output dtype.  When I swap these two code chunks: type conversion (lines 194-198) before the masking (lines 189-192), I get the expected result.  But I'm guessing I'm introducing some unintended consequences.

One other minor point: In order to use my specified profile nodata value, I had to first cast it to an int (line 192):

  res = res.filled(int(kwargs['nodata'])))

Thanks for any advice,

You may get better results using numpy.where, like "(where (>= (read 1) 0.5) 1 0)".

I'll dig into the filling code, that looks like a bug to me.

Sean Gillies

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