Hello everyone, I maked NDVI raster using RasterExpressionEvaluator and I want to clip it with a shapefile area. I use RasterBandNoDataSetter tranformer to remove all NoData Value (pixel = 0) but in my area, I have some pixels with NDVI value = 0 , so they are removed also. Have you got any idea to avoid this ?
Thks everyone for your help 🙂
+64Put the RasterBandNodataSetter before the Clipper instead of after it. Then only the part which is clipped away will be nodata.
Put the RasterBandNodataSetter before the Clipper instead of after it. Then only the part which is clipped away will be nodata.
thanks for your answer. Effectively I read this method in another topic but doesn't work as I want! You can see here my Workbrench if you want
+64thanks for your answer. Effectively I read this method in another topic but doesn't work as I want! You can see here my Workbrench if you want
Bummer. Are you sure the cells do not already have NoData values to begin with? Or result from the RasterExpressionEvaluator?
thanks for your answer. Effectively I read this method in another topic but doesn't work as I want! You can see here my Workbrench if you want
As input I have images which are composed by 5 bands so for NDVI calculation I use band 3 and band 0 (as you can see in attachment) maybe the problem is alpha band? 
+40You have two options:
Use a different noData value that is not covered by your valid data range
Use an alpha band to identify NoData areas.
You have two options:
Use a different noData value that is not covered by your valid data range
Use an alpha band to identify NoData areas.
I agree with you to use an alpha band, nonetheless I already use the band 3 which is an alpha band.. So maybe is it possible to convert the alpha band to band 4 ? Can you develop your proposition please ?
+40I agree with you to use an alpha band, nonetheless I already use the band 3 which is an alpha band.. So maybe is it possible to convert the alpha band to band 4 ? Can you develop your proposition please ?
It would depend on the software you are using whether or not you can specify the alpha band on a multiband (>4) image.
If it were me, I would create the NDVI as a separate image, so there would only be two bands, the NDVI and alpha, rather than add the NDVI band to the existing 5-band image.
I agree with you to use an alpha band, nonetheless I already use the band 3 which is an alpha band.. So maybe is it possible to convert the alpha band to band 4 ? Can you develop your proposition please ?
Yes I think it seems to me to be the best and cleanest solution to create firstly my NDVI image and add alpha band ! So after my RasterExpressionEvaluator I use RasterBandAdder transformer and which valuers can I specify ? NoData value will be the value that I will remove after that's it ?
+40I agree with you to use an alpha band, nonetheless I already use the band 3 which is an alpha band.. So maybe is it possible to convert the alpha band to band 4 ? Can you develop your proposition please ?
It shouldn't be that complicated.
RasterExpressionEvaluator, band 0 is your NDVI band and the interpretation is presumably REAL32 to allow for a range of -1.0 to 1.0.
Band 1 is your alpha channel, set the interpretation to Alpha8 and the value to 255.
Send the results to your clipper. You do not need to set a NoDataValue, if there is one on the original data, it should be removed prior to the RasterExpressionEvaluator.
I agree with you to use an alpha band, nonetheless I already use the band 3 which is an alpha band.. So maybe is it possible to convert the alpha band to band 4 ? Can you develop your proposition please ?
I tried to add alpha band before clipping, to specify my NoDataValue, and after clipping, I remove with RasterBandNodataSetter my value of NoDataValue, but when I want to write (save) TIF file, I have this error.
have you got a solution ?
