Feature request: implement scaleclip switch in gdal_transform

[aloboa]

I think it would be useful having -scale complemented by a parameter scaleclip to indicate "Clip output values to the effective range dst_min to dst_max defined in -scale"

[dselivanov]

I would like to work on this. @rouault could you please point where scale is calculated? (I'm new to GDAL source base).

[rouault]

@rouault could you please point where scale is calculated?

maybe surprisingly, this will not be a completely trivial change. The scaling is actually performed by the GDAL VRT driver.
gdal_translate pass the (offset, scale) pair at

gdal/apps/gdal_translate_lib.cpp

Line 1984 in 6e6aff4

poSource->SetLinearScaling(dfOffset, dfScale);

(they're computed a few lines before from src_min src_max dst_min dst_max at

gdal/apps/gdal_translate_lib.cpp

Line 1957 in 6e6aff4

dfScale = (dfScaleDstMax - dfScaleDstMin)

)
and the scaling computation in the VRT driver is done at

gdal/frmts/vrt/vrtsources.cpp

Line 2845 in 6e6aff4

fResult = static_cast<WorkingDT>(

.
For a -scaleclip option to work, you'll have to modify the VRT serialization/deserialization from/to XML to store the src_min src_max dst_min dst_max parameters (this is already done for the exponential scaling, so that should be reused. you'll find that in the vrtsources.cpp file), as well as the option to clip.

[init931]

Any updates on implementing this feature?