[gdal-dev] Set/Get Scale and Offset in GDALRasterBand

[Ray Gardener]

The functions are to allow mapping between logical and physical pixel 
values. This is very common in e.g. elevation DEMs.

Applying them is done by the calling code. At least, I haven't seen any 
routines in GDAL that
would apply them for you.

Ray


On 6/22/2015 7:50 AM, Alexander Bobkov wrote:
> Hi,
>
> What is the intended usage of methods 
> SetScale/GetScale/SetOffset/GetOffset of the GDALRasterBand class?
>
> Documentation says that
>>
>> This value (in combination with the GetOffset() 
>> <http://www.gdal.org/classGDALRasterBand.html#ab62e0761dde3e3b76f83155920275e4f> 
>> value) is used to transform raw pixel values into the units returned 
>> by GetUnits(). For example this might be used to store elevations in 
>> GUInt16 bands with a precision of 0.1, and starting from -100.
>>
>> Units value = (raw value * scale) + offset
>>
>
> Who is responsible for applying the formula: client code before/after 
> RasterIO operation, or driver code inside IReadBlock/IWriteBlock methods?
>
> Best regards,
> Alexander Bobkov
>
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20150622/56713a8f/attachment.html>