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Hi, I converted a raster image with the RasterPaletteGenerator. The new file can be easily filtered in QGIS using the Raster calculator (I only want one value out of the 255). However, I cannot find an equivalent tool in FME. Thanks for your help. Os

  • September 7, 2020
  • 2 replies
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ozuritah
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I've tried using the raster selector but it always fails (probably because I do not know how to correctly introduce the parameters)

I am attaching a print screen of the Raster Calculator from QGIS with the "Expression" I used to filter my raster image. Thanks

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2 replies

takashi
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  • takashiCelebrity
  • 7843 replies
  • September 7, 2020

Hi @ozuritah​ , the RasterExpressionEvaluator could be what you are looking for.

Why not inspect features with Visual/Data Preview and Feature/Record Information before writing them into a destination dataset?
ozuritah
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  • ozuritahParticipant
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  • September 9, 2020

Hi @ozuritah​ , the RasterExpressionEvaluator could be what you are looking for.

Thanks @Takashi Iijima​ but after countless attempts I am not able to get the RasterExpressionEvaluator to work as I wish. My raster/palette has one band with 255 colours . I want to filter the file so that I end up having a black and white image where white corresponds to colour 5 (for example) and all the other colours become black. Then I can easily polygonise the black and white raster image.

As mentioned, I did it with the Raster Calculator in QGIS but it would be more efficient and fast if I could do it in FME.

Thanks, Oscar

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