topic Re: Use Con with two rasters in Geoprocessing Questions

Use Con with two rasters

mody_buchbinder — Wed, 30 Jun 2021 13:35:21 GMT

Hello all

I am trying to write a python program that will create a new raster by condition of two rasters.

I can do it with the con function like this:

res = arcpy.sa.Con((Raster1 == 0 & Raster2 == 0),1,0)

For the con function you need to create a Raster() before you can use it and then save the results.

From the other hand arcpy.gp.con_sa can get a path of tif as parameter and the final result name is parameter.

I could not find the way to put two rasters in the condition (it is usually "value == 0" of the raster in the new parameter.

Any ideas?

Re: Use Con with two rasters

JayantaPoddar — Wed, 30 Jun 2021 14:30:06 GMT

Not sure if I am able to understand the concern.

Are you looking for an expression like?

arcpy.sa.Con(((Raster1 == 0) & (Raster2 == 0)), 1, 0)

Re: Use Con with two rasters

DavidPike — Wed, 30 Jun 2021 14:59:47 GMT

What do you mean by python program? If you mean as a python script tool, can't the output filename when using .save() just be used as a parameter? If you mean as a GP tool/task, then the result object of .save() would just be put as arcpy.SetParameter(x) and the output set as derived (a while since I've done that so may not be exactly correct).

Re: Use Con with two rasters

DanPatterson — Wed, 30 Jun 2021 15:04:14 GMT

Did you try something like this... pick one or the other to see if it works... they lead to the same code in any event

r0 = "c:/path/some.tif" r1 = "c:/path/another.tif" arcpy.gp.con_sa((Raster(r0) == 0) & (Raster(r1) == 0), 1, 0) # ---- or!! arcpy.sa.Con((Raster(r0) == 0) & (Raster(r1) == 0), 1, 0)

Re: Use Con with two rasters

DanPatterson — Wed, 30 Jun 2021 15:16:36 GMT

or a numpy lesson... verbose, showing that arcpy plays nice with numpy

a1 = arcpy.RasterToNumPyArray("c:/temp/a0.tif") b1 = arcpy.RasterToNumPyArray("c:/temp/b0.tif") whr = np.logical_and((a1==0), (b1==0)) out = np.where(whr, 1, 0) a1 array([[1, 0, 3, 0], [3, 2, 1, 1], [4, 3, 0, 3], [2, 0, 0, 1], [2, 4, 2, 1]]) b1 array([[1, 1, 2, 4], [3, 1, 0, 3], [4, 2, 0, 1], [3, 4, 1, 2], [1, 0, 2, 0]]) whr array([[False, False, False, False], [False, False, False, False], [False, False, True, False], [False, False, False, False], [False, False, False, False]]) out array([[0, 0, 0, 0], [0, 0, 0, 0], [0, 0, 1, 0], [0, 0, 0, 0], [0, 0, 0, 0]])

my favorite raster goto 😉

Re: Use Con with two rasters

mody_buchbinder — Thu, 01 Jul 2021 13:24:26 GMT

Hi Dan

Please read my previous question here: https://community.esri.com/t5/python-questions/what-is-the-way-to-call-spatial-analysis-tools-in-arcmap-from/td-p/1037005

The arcpy.sa.con_sa have different parameters and the first parameter is the input raster so you cannot gives two rasters.

I will look into the numpy

Thanks

Re: Use Con with two rasters

DanPatterson — Thu, 01 Jul 2021 14:17:01 GMT

Mody, if you want to bring the raster back in, check the optional parameters for rastertonumpyarray and numpyarraytoraster

RasterToNumPyArray—ArcGIS Pro | Documentation

RasterToNumPyArray (in_raster, {lower_left_corner}, {ncols}, {nrows}, {nodata_to_value})

NumPyArrayToRaster—ArcGIS Pro | Documentation

NumPyArrayToRaster (in_array, {lower_left_corner}, {x_cell_size}, {y_cell_size}, {value_to_nodata}, {mdinfo})

This allows you to maintain the spatial location and nodata values.

the lower left corner has examples in the help eg

lowerLeft = arcpy.Point(in_raster.extent.XMin, in_raster.extent.YMin)