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I have generated a raster that has integer data values between 1 and 6 and needs a nodata value.  

As the RasterInterpretationCoercer has a “Data Interpretation Type” of “Int8” I thought my task would be as simple as:

  1. Use the “RasterBandNodataSetter” to set the Nodata Value of -128.
  2. Use the “RasterInterprationCoercier” with the Data Interpreation Type of “Int8”.
  3. Use the GEOTIFF writer to output a tif file.

When I try this type of workflow and then use FME to read the generated tif file, I find that the raster band is written with the type Uint8 and that my data value has been changed to 128.  I am using FME 2025.0.3.

Is it possible to get the GEOTIFF writer to write raster data with the datatype of int8 and a negative Nodata value?  If not, which raster types in FME will allow this?

Hi ​@philipwhitten ,

In my quick test, I wasn't able to reproduce the issue. Could you please take a look at the attached workspace example and see if there are any different conditions from yours?

Thanks so much ​@takashi.  I have downloaded your workspace and I agree that your output is what I want to achieve.  I am going through all of my settings, but haven’t yet isolated which detail is giving me the unwanted behaviour with my original workspace. 

For reasons that I don’t yet understand, not only is my data ouput uint8 instead of int8, but, my output file also has a pallete which I know shouldn’t be there - and I know that palletes can’t work with int8.  I have attached my current workspace and could provide some cut down input raster files if necessary.

For my workspace, this is what FME is telling me when I read the generated tiff file (note uint8 and pallete):

 

This is the raster attributes immediately before the GEOTIFF writer (note int8 and no Pallete):

 

I have worked out the cause was in the GEOTIFF feature writer’s Advanced parameters.  I had the “Photometric Interpretation” = “MinIsWhite”. When I change this setting to “Auto” I get the int8 datatype that I want.

Good to hear the issue has been resolved. Cheers!

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