Non-transparent rendering of a raster outside the bounding box

[nicokant]

Hi,
I'm struggling while trying to understand why titiler renders a non-transparent background outside the bounding box, while it's correctly rendered as transparent inside the bounding box.

In particular the URL I'm using is: /cog/tilejson.json?colormap_name=ylorrd&rescale=-1,15&bidx=1&minzoom=0&url=PATH_TO_COG

The raster dataset has a NODATA value set to -128

The response is:

{
   "tilejson":"2.2.0",
   "version":"1.0.0",
   "scheme":"xyz",
   "tiles":[
      "https://SERVER/cog/tiles/WebMercatorQuad/{z}/{x}/{y}@1x?colormap_name=ylorrd&rescale=-1%2C15&bidx=1&url=PATH_TO_COG"
   ],
   "minzoom":0,
   "maxzoom":12,
   "bounds":[
      10.546875000000014,
      59.7563950493563,
      10.986328125000014,
      60.02095215374802
   ],
   "center":[
      10.766601562500014,
      59.888673601552156,
      0
   ]
}

I checked the bounds and they are correct. I also tried to specify nodata=-128 as parameter, but the result didn't change...

Has anyone had the same issue?
Thank you!
Niccolò

[vincentsarago]

pretty hard to tell without having access to the COG itself. Might be also useful to know which version of titiler/rio-tiler you're running.

If you can't change the cog as is you can checkout https://github.com/cogeotiff/rio-faux

[nicokant]

I was using 0.17.0 and it seems that in 0.21.1 it's fixed 👍

[davidbrochart]

I'm not sure it's the right place, but I was wondering how to render a transparent tile when it is outside the bounds, instead of the server throwing TileOutsideBounds?

[vincentsarago]

normally TileOutsideBounds should return a 404 (https://github.com/developmentseed/titiler/blob/main/src/titiler/core/titiler/core/errors.py#L35)

I'm not sure what you mean with render

[davidbrochart]

Yes I could see 404 on these tiles but for some reason they didn't appear as transparent. Anyway that's solved now, thanks.