add /collections/{collection_id}/items/{item_id}/assets/{asset_id} endpoints

[vincentsarago]

Right now we use query parameter to pass the asset we want to visualize

/collections/{collection_id}/items/{item_id}/preview.png?assets={asset_id}&asset_bidx={asset_id}|1,2,3

but in theory we could do something like

/collections/{collection_id}/items/{item_id}/assets/{asset_id}/preview.png?&asset_bidx={asset_id}|1,2,3
/collections/{collection_id}/items/{item_id}/assets/{asset_id}/preview.png?bidx=1,2,3

• It kinda make sense to have the /assets/{asset_id} suffix for one asset but what if we want to combine more than one?

/collections/{collection_id}/items/{item_id}/assets/B01,B02,B03/preview.png

I'm not sure about using , as assets delimiter. what are other options?

• what about expression?

This is tricky but we could keep the same structure and add an expression=True parameter

/collections/{collection_id}/items/{item_id}/assets/B01+B02/preview.png?expression=True

we could also do something like:

/collections/{collection_id}/items/{item_id}/expression/B01+B02/preview.png

[drwelby]

/collections/{collection_id}/items/{item_id}/assets/B01,B02,B03/preview.png feels like it's overloading REST concepts.

/collections/{collection_id}/items/{item_id}/assets/{asset_id}/preview.png?bidx=1,2,3 makes sense for previewing one asset.

What would follow for me would be:

/collections/{collection_id}/items/{item_id}/assets/preview.png?asset_bidx={asset_id},{asset_id},{asset_id}

[vincentsarago]

🙏 thanks @drwelby

/collections/{collection_id}/items/{item_id}/assets/preview.png?asset_bidx={asset_id},{asset_id},{asset_id}

We tend to use assets={asset_id}&assets={asset_id}&assets={asset_id} instead of , delimited values for query-string, which is why I though that using /assets/{asset_id},{asset_id},{asset_id}/preview.png notation.

We also have to keep in mind that:

• users might want to mix assets and select specific bands from assets
• assets can be one bands
• expression can be for one asset or multiple assets (and we can use the asset_as_band=True option)

[vincentsarago]

😅 just realizing that we can already do most of this

from starlette.requests import Request
from titiler.pgstac.dependencies import get_stac_item
from titiler.core.factory import TilerFactory
from typing_extensions import Annotated
from fastapi import FastAPI

def ItemPathParams(
    request: Request,
    collection_id: Annotated[str, Path(description="STAC Collection Identifier")],
    item_id: Annotated[str, Path(description="STAC Item Identifier")],
    asset_id: Annotated[str, Path(description="STAC Asset Identifier")],
) -> str:
    """STAC Item dependency."""
    item = get_stac_item(request.app.state.dbpool, collection_id, item_id)
    asset_info = item.assets[asset]
    return asset_info.get_absolute_href() or asset_info.href,

app = FastAPI()
asset = TilerFactory(
    path_dependency=ItemPathParams,
    router_prefix="/collections/{collection_id}/items/{item_id}/assets/{asset_id}",
)
app.include_router(
    asset.router, tags=["STAC Asset"], prefix="/collections/{collection_id}/items/{item_id}/assets/{asset_id}"
)

☝️ will not allow mixing assets but for this you'll want to go the /item way 🙏