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RasterExpressionEvaluator Expression to select raster GRAY8 values

  • July 24, 2025
  • 2 replies
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galigis
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Hi All,

I often encounter difficulties when attempting to select specific raster values using FME. I am currently working with a raster dataset that contains two bands, and I need to isolate the following values:

  • Band 0 (GRAY8) = 3
  • Band 0 (GRAY8) = 4

Could you please advise on the appropriate expression to use within the RasterExpressionEvaluator to achieve this selection?

Thanks :)

Best answer by takashi

Hi ​@galigis ,

I suppose @if function is what you want. For example, if you would like to keep only 3 or 4 and  set a specific value - e.g. 0 to other cells, this expression works for you.

@if(A[0]==3 || A[0]==4, A[0], 0)

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2 replies

takashi
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  • takashiCelebrity
  • Best Answer
  • July 24, 2025

Hi ​@galigis ,

I suppose @if function is what you want. For example, if you would like to keep only 3 or 4 and  set a specific value - e.g. 0 to other cells, this expression works for you.

@if(A[0]==3 || A[0]==4, A[0], 0)

Why not inspect features with Visual/Data Preview and Feature/Record Information before writing them into a destination dataset?
galigis
galigis
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  • galigisEnthusiast
  • Author
  • Enthusiast
  • July 24, 2025

Spot on! :) thanks ​@takashi 

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