From the url you provided I can tell that the getCapabilities is wrongly advertising it supplies png, when it actualy supplies jpeg rasters.

<Format>image/jpgpng</Format> is the definition on line 64.

QGIS has a diferent method of reading rasters, FME needs to know in advanced what the raster format is. As it's trying to read png from jpeg it gets stuck.

I suggest a workaround:

Use WebMapTiler to create some GoogleMapsCompatible tiles for your zoom level (it requires a raster as input, just put your area of input polygon or bbox through NumericRasterizer), send the tiles to HTTPCaller set to GET https://tiles1.geoserve.eu/Mosaics/tieserver/20220531_20220416_SV_RD_8bit_RGBMosaic_50cm_Nederland/@Value(_zoom_level)/@Value(_tile_column)/@Value(_tile_row) - the url needed for WMTS that uses the default output attributes of WebMapTiler, send the output to a BoundsExtractor to get x/y min/max needed to georeference the downloaded rasters, to RasterReplacer set as JPEG and Blob atribute set as _responce_body, and finaly send this to a RasterGeoreferencer set as Extents with the necesary attributes from BoundsExtractor.

See also attached workspace.

That is incredibly insightful and very, very helpful, thank you so much!!

Hello @michiedem​ , thanks for posting! @caracadrian​'s workaround looks good! The image/jpgpng shouldn't be an issue, FME should be able to work with this as of FMEENGINE-73560. I think that means it gets both JPG and PNG so it should be able to read whatever comes from the server.

I think the error your seeing is thrown by the reader when it recieves no image at a tile. If you were to copy & inspect the path to the .tmp in the error message, I think you'd see something like this:

I have filed this as FMEENGINE-74041, I'll update the thread as I can. You should still be able to run and cache the data at lower resolutions with these errors present in the logfile, mind you it doesn't seem like this service has a ton of images at lower resolutions. If you're trying to read from super high resolutions, like 18, I'd consider using a bounding box in Tile Selection to reduce the amount of tiles you're grabbing, which should ultimately reduce the number of errors you see. Hopefully this is clearer, Kailin.