Add support for .bil format

[Sgambe33]

Hello, would it be possible to add .bil format? Mainly because I would like to use Titiler along with ITowns and the latter uses .bil files for elevation layers.

[vincentsarago]

is the .bil format supported by GDAL natively?

I don't see mention to .bil in http://www.itowns-project.org 🤷

are you talking about https://desktop.arcgis.com/en/arcmap/latest/manage-data/raster-and-images/bil-bip-and-bsq-raster-files.htm ? For what I'm reading this BIL format is in fact 2 files: one .bil binary and one .hdr which to me seems to be the same format referenced in https://gdal.org/en/latest/drivers/raster/envi.html#raster-envi

To me seems that it could be natively supported but will required some work on rio-tiler and titiler, Could GeoTIFF be something you can use instead?

[Sgambe33]

You are right, .bil is not explicitly mentioned in itowns but is present in some examples/docs (https://www.itowns-project.org/itowns/docs/#api/Layer/ElevationLayer). Is also one of the only two ways of displaying elevation data, the other is by using color encoded height but that seems to be providing really low performance.

I've tried using .bil files generated by GDAL (which supports them) but tiling is a bit of a hassle to do manually. Furthermore the .hdr file is not required by itowns.

I've asked if it was possible to add because there's literally no one that provides such format in tiling programs. The only one I found is a french program but the docs are all in french and it's not straightforward to get it working (https://github.com/rok4/server).

[vincentsarago]

It might be easier to create a custom endpoint like

from typing import Literal
from attrs import define
from pydantic import Field
from fastapi import Depends, Path
from starlette.responses import Response
import rasterio
from titiler.core import factory
from typing_extensions import Annotated
import numpy


@define(kw_only=True)
class TilerFactory(factory.TilerFactory):

    def tile(self):  # noqa: C901
        """Register /tiles endpoint."""

        @self.router.get("/tiles/{tileMatrixSetId}/{z}/{x}/{y}.bil", response_class=Response)
        @self.router.get("/tiles/{tileMatrixSetId}/{z}/{x}/{y}@{scale}x.bil", response_class=Response)
        def tile(
            z: Annotated[
                int,
                Path(
                    description="Identifier (Z) selecting one of the scales defined in the TileMatrixSet and representing the scaleDenominator the tile.",
                ),
            ],
            x: Annotated[
                int,
                Path(
                    description="Column (X) index of the tile on the selected TileMatrix. It cannot exceed the MatrixHeight-1 for the selected TileMatrix.",
                ),
            ],
            y: Annotated[
                int,
                Path(
                    description="Row (Y) index of the tile on the selected TileMatrix. It cannot exceed the MatrixWidth-1 for the selected TileMatrix.",
                ),
            ],
            tileMatrixSetId: Annotated[
                Literal[tuple(self.supported_tms.list())],
                Path(
                    description="Identifier selecting one of the TileMatrixSetId supported."
                ),
            ],
            scale: Annotated[
                int,
                Field(
                    gt=0, le=4, description="Tile size scale. 1=256x256, 2=512x512..."
                ),
            ] = 1,
            format: Annotated[Literal["bil"], "Output file format"] = "bil",
            src_path=Depends(self.path_dependency),
            reader_params=Depends(self.reader_dependency),
            tile_params=Depends(self.tile_dependency),
            layer_params=Depends(self.layer_dependency),
            dataset_params=Depends(self.dataset_dependency),
            env=Depends(self.environment_dependency),
        ):
            """Create map tile from a dataset."""
            tms = self.supported_tms.get(tileMatrixSetId)
            with rasterio.Env(**env):
                with self.reader(
                    src_path, tms=tms, **reader_params.as_dict()
                ) as src_dst:
                    image = src_dst.tile(
                        x,
                        y,
                        z,
                        tilesize=scale * 256,
                        **tile_params.as_dict(),
                        **layer_params.as_dict(),
                        **dataset_params.as_dict(),
                    )

            content = image.render(
                add_mask=False,
                img_format="ENVI",
                INTERLEAVE="BIL",
            )
            
            dtype_info_registry = {"c": numpy.finfo, "f": numpy.finfo, "i": numpy.iinfo, "u": numpy.iinfo}
            kind = numpy.dtype(dtype).kind
            info = dtype_info_registry[kind](dtype)
            
            return Response(content, media_type=f"image/x-bil;bits={info.bits}")

[vincentsarago]

The other issue about making this part of titiler would be that the media_type has be be dynamically created depending on the datatype, so it's just easier to create custom endpoint/extension for this

[Sgambe33]

Thx, in this way everything works!

[vincentsarago]

Feel free to share what you are doing with this, always fun to see how people are using TiTiler :-)