[gdal-dev] Proposal: gdal_muladd.py

[Greg Coats]

Regarding the diff function
"diff": computes the difference between 2 raster bands (b1 - b2)
Since the result of diff could be a negative number, for example 99-150=-51, I suggest that there be an additional function that provides the absolute value of diff, which would be 51 in this example.
Greg

On Jan 31, 2010, at 12:18 PM, Antonio Valentino wrote:

> Hi Matt,
> 
> Il giorno Mon, 25 Jan 2010 20:57:58 -0600
> Matt Klaric <matt at klaric.com> ha scritto:
> 
>> On Mon, Jan 25, 2010 at 8:38 PM, Frank Warmerdam
>> <warmerdam at pobox.com>wrote:
>> 
>>> I don't think the VRT approach supports actually adding
>>> different images together, only overlaying and rescaling.
>>> 
>>> 
>> However, pixel functions could be used in a VRT file to accomplish the
>> desired outcome.
>> 
>> --matt
> 
> Indeed, it would require a pixel function for sum and the ScaleRatio
> property of ComplexSource.
> 
> I have just submitted a patch 
> 
> http://trac.osgeo.org/gdal/ticket/3367
> 
> that provides a set of standard pixel functions, including sum (of 2
> or more raster bands).
> 
> Using this set of functions it should be quite easy to write a python
> program that performs generic bands arithmetic.
> 
> Best regards.
> 
> -- 
> Antonio Valentino
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