[gdal-dev] Precision about scale/offset element in VRT file

[Chaitanya kumar CH]

Output pixel value = (raw pixel value * scale) + offset

On Fri, Mar 23, 2012 at 5:44 PM, Saâd HESSANE <saad.hessane at gmail.com>wrote:

> Ok, thank you again Chaitanya,
>
> But what is the function of this two element?
>
>
> 2012/3/23 Chaitanya kumar CH <chaitanya.ch at gmail.com>
>
>> Saâd,
>>
>> A VRT raster band can be derived from more than one source.
>>
>> Offset and Scale elements apply to the whole VRT raster band.
>> The ScaleOffset and ScaleRatio perform the same task but it is done only
>> on that particular ComplexSource.
>>
>> On Fri, Mar 23, 2012 at 3:43 PM, Saâd HESSANE <saad.hessane at gmail.com>wrote:
>>
>>> Hy all,
>>>
>>> The vrt format allow defining the scale and offset element. But the
>>> documentation is not clear about that :
>>>
>>>    - *Offset*: This optional element contains the offset that should be
>>>    applied when computing "real" pixel values from scaled pixel values on a
>>>    raster band. The default is 0.0.
>>>    - *Scale*: This optional element contains the scale that should be
>>>    applied when computing "real" pixel values from scaled pixel values on a
>>>    raster band. The default is 1.0.
>>>
>>> What that it's mean ? If the value of offset is 1 what that it's change?
>>>
>>> And this two elements are use in the *VRTRasterBand* element. What
>>> about *ScaleOffset* and *ScaleRatio* in the *ComplexSource* element?
>>>
>>> Thank you.
>>>
>>> _______________________________________________
>>> gdal-dev mailing list
>>> gdal-dev at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>>>
>>
>>
>>
>> --
>> Best regards,
>> Chaitanya kumar CH.
>>
>> +91-9494447584
>> 17.2416N 80.1426E
>>
>
>


-- 
Best regards,
Chaitanya kumar CH.

+91-9494447584
17.2416N 80.1426E
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