[GRASS-user] speeding up context evaluation...

[Hufkens Koen]

Hi list,

for a validation exercise I need to extract the class values around certain pixel location.

I have a map with all the locations (numbered) and a map with the validation map.

The code you find below is the one I came up with to get this information (only output to terminal for the moment).

However, this code includes a loop and is terribly slow. Has anyone an idea how to speed things up?

Kind regards,
Koen

---------- my code -------------

#!/bin/bash
# 
###########################################################################################################################
# 
# Get context around pixels...
#
# !!! Bash script only works within the GRASS terminal !!!
#
###########################################################################################################################


#
# get number of pixels in location file... write to variable $pixels...
#

pixels=`r.info -r map=$1 | tail -n +2 | sed 's/max=//'`

echo "their are $pixels groundtruth points..."

for i in `seq 1 $pixels`;
do

echo "evaluating pixel $i of $pixels pixels..."

#
# Make MASK based upon pixel number evaluate one at a time. Mask name is MASK and patch.mask
# after renaming... If kept as MASK it will apply to all operations and is a system wide setting (not wanted)...
#

r.mask -o input=$1 maskcats=$i --quiet
g.rename rast=MASK,pixel.mask --overwrite --quiet

#
# create buffer around pixel value...
#

r.buffer input=pixel.mask output=tmp.buffer distances=4 units=meters --overwrite --quiet

#
# writes temporary reclass rules file...
#

echo "1 = NULL" > tmp.rules
echo "2 = 1" >> tmp.rules
echo "end" >> tmp.rules

#
# reclass context values using rules above...
#

r.reclass input=tmp.buffer output=context.mask rules=tmp.rules --overwrite

#
# calculate category statistics for pixel and context location...
#

r.mapcalculator amap=pixel.mask bmap=$2 formula=A*B outfile=pixel.category help=- --overwrite --quiet 
echo "pixel data..."
r.stats -c -n input=pixel.category fs=space nv=* nsteps=255 

r.mapcalculator amap=context.mask bmap=$2 formula=A*B outfile=context.category help=- --overwrite --quiet 
echo "context data..."
r.stats -c -n input=context.category fs=space nv=* nsteps=255 

done

#
# clean up tmp files...
#

rm tmp.rules
g.remove rast=pixel.mask
g.remove rast=context.mask

echo "!!!DONE!!!"
echo "#########################################################################"
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