05-25-2018 03:27 AM
I have orthophoto stored as single 4 band ECW file (~150 GB).
There is large areas with no data stored as 255 pixels.
Is there any way to change all 255 pixels to 0?
05-25-2018 04:34 AM
It can be done using Spatial Modeler, mainly with the Replace No Data With operator.
If "255" value is defined as NoData, so model will look like below:
Let me know if that will work for you.
05-25-2018 05:32 AM - edited 05-25-2018 05:34 AM
Remember to make sure you don't have any (valid) 0s in your imagery first! You'll probably also want to set 0 as the output NoData value to use in the Raster Output operator.
You may wish to review the various discussions on the topic of NoData before proceeding:
05-25-2018 06:07 AM
That said - if your original image is an ECW I'm surprised that it's not using a Mask (as opposed to a data value) to store the NoData locations.. That would be the usual way to store NoData in ECW.
If it's not using a Mask have you tried adding one? If it's a v2 ECW you can add a mask after the file has been created (using Create ECW Transparency). You can't do this if it's a v3 ECW because a mask already exists in the file (ECW v3 is always created with a mask layer). Which means you probably have a v2 if the file has value-based NoData rather than mask-based.