topic Extract single bands from ECW image using Arcpy in Python Questions

Extract single bands from ECW image using Arcpy

AnthonyCheesman1 — Thu, 30 May 2019 11:07:07 GMT

Hi folks

ive also asked this over at the Spatial Analyst group with no response, so I thought I’d try here.

im looking for a Pythonic way to extract a single band from a multi band ECW image. The ECW part is important, as every time I try to run an ArcToolbox tool on the data, Arcmap immediately crashes. I get the same result using IDLE and arcpy. The only success I’ve had on the Desktop front was by loading the specific band, and then right clicking > Export Data.

the one bit of success I had was creating a faster object using arcpy.sa.Raster and then saving this to a different workspace. However this copied all bands over, not just the band I had selected for the raster object. (path/image.ecw/Red for example).

Why am I doing this? I need to be able to batch generate a heap of NDVI outputs, where I need to extract the red band from the VIS image and the IR band from the IR image.

Any my suggestions will be gratefully appreciated.

Thanks

Ant

Re: Extract single bands from ECW image using Arcpy

DanPatterson_Retired — Thu, 30 May 2019 12:43:26 GMT

what version of ArcMap? or is it ArcGIS Pro you are using. Non-English characters? particular locale?

I ask because

BUG-000110931: Unable to load Enhanced Compression Wavelet (ECW) fi..

plus a load more in the last year

ECW bug list for the last year

Re: Extract single bands from ECW image using Arcpy

AnthonyCheesman1 — Thu, 30 May 2019 21:38:57 GMT

Hi Dan

I’ve had the same issue with 10.3.1 and 10.5.1. Australia, en-au. No non-English characters.

That link above re: 10.6.1 is very interesting, not the least because we are (were?) about to do a system-wide migration to 10.6.1 - that may knock it on the head.

After I posted yesterday evening, I got to thinking about any other libraries that may be able to assist, and had a hunt around. It looks as though GDAL should be able to open the images and extract the bands, which I could then load as arrays in numpy to do the required algebra for the NDVI analysis. I haven’t tried yet but it sounds like a promising avenue to investigate.

Thanks

Anthony

Re: Extract single bands from ECW image using Arcpy

DanPatterson_Retired — Fri, 31 May 2019 02:46:26 GMT

Anthony, gdal is within the esri anaconda distribution of ArcGIS Pro... check to see if it is there for ArcMap. Just about everbody uses it at some level