[gdal-dev] Why is saving an array to ENVI file format using SaveArray so slow?

[mike c]

Dear GDAL Developers

 

I’m  finding that when
saving  a relatively small array (shape =
128,4000,128  ie 128 band x 4000 lines x
128 columns of float data = 256Mb total)  to a ENVI file format using the call:

 

gdalnumeric.SaveArray(img,strf_out,'ENVI')

 

performance is extremely slow (~260 seconds).  When I save the same array to Geotif  format using;

 

gdalnumeric.SaveArray(img,strf_out,'GTIFF')

 

the operation
takes  ~24 seconds which is much more
acceptable.  

 

I’m currently
using gdal version 1.11.1 .  

 

My question to
the forum is then  -why is there such a
large discrepancy between the performance of the two operations and is there a way
to improve the performance when writing an array to  an ENVI file format?  

 

I have tried changing
the GDAL Cache options but performance doesn’t seem to alter.  When profiling the code which saves the array
to GeoTIFF format I get the output contained in the attached file timing_savearray_GTIFF.txt.  When profiling the code which saves the array
to ENVI format I get the output contained in the attached file timing_savearray_ENVI.txt

 

I would like to
save the data to ENVI file format.  Your
thoughts on this matter would be appreciated.

 

Thanks

 

Regards 

mike 		 	   		  
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