Custom Layers
Goal: Create a Custom TiTiler with a limited set of supported layers
requirements: titiler.core
How:
The idea is to create a set of endpoints with a /layers/{layer_id} prefix and a set of configuration, e.g
config = {
"layer_1": {
"url": "dataset_1 url",
"indexes": [1],
"render": {
"rescale": [(0, 1000)],
"colormap_name": "viridis"
}
},
...
}
We then use custom set of endpoint dependencies to get the layer configuration and inject the parameters.
import json
from dataclasses import dataclass, field
from typing import Dict, Literal, Annotated, Optional, Sequence
from fastapi import FastAPI, Path, HTTPException, Query
from rio_tiler.colormap import ColorMaps
from rio_tiler.colormap import cmap as default_cmap
from rio_tiler.colormap import parse_color
from starlette.requests import Request
from titiler.core import dependencies
from titiler.core.errors import DEFAULT_STATUS_CODES, add_exception_handlers
from titiler.core.factory import TilerFactory
# Layers Configuration
available_layers = {
"red": {
"url": "https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B04.tif",
"render": {
"rescale": [
(0, 1000),
],
},
},
"green": {
"url": "https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B03.tif",
"render": {
"rescale": [
(0, 1000),
],
},
},
"bleue": {
"url": "https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B02.tif",
"render": {
"rescale": [
(0, 1000),
],
},
},
}
# VRT of bands B04, B03, B02, and B05 files
# gdalbuildvrt vrt.vrt /vsicurl/https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B{04,03,02,08}.tif -separate
# cat vrt.vrt | tr -d '\n' | tr -d ' '
vrt_rdbnir = '<VRTDataset rasterXSize="10980" rasterYSize="10980"> <SRS dataAxisToSRSAxisMapping="1,2">PROJCS["WGS 84 / UTM zone 21S",GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-57],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",10000000],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["Easting",EAST],AXIS["Northing",NORTH],AUTHORITY["EPSG","32721"]]</SRS> <GeoTransform> 6.0000000000000000e+05, 1.0000000000000000e+01, 0.0000000000000000e+00, 7.3000000000000000e+06, 0.0000000000000000e+00, -1.0000000000000000e+01</GeoTransform> <VRTRasterBand dataType="UInt16" band="1"> <NoDataValue>0</NoDataValue> <ComplexSource> <SourceFilename relativeToVRT="0">/vsicurl/https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B04.tif</SourceFilename> <SourceBand>1</SourceBand> <SourceProperties RasterXSize="10980" RasterYSize="10980" DataType="UInt16" BlockXSize="1024" BlockYSize="1024" /> <SrcRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <DstRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <NODATA>0</NODATA> </ComplexSource> </VRTRasterBand> <VRTRasterBand dataType="UInt16" band="2"> <NoDataValue>0</NoDataValue> <ComplexSource> <SourceFilename relativeToVRT="0">/vsicurl/https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B03.tif</SourceFilename> <SourceBand>1</SourceBand> <SourceProperties RasterXSize="10980" RasterYSize="10980" DataType="UInt16" BlockXSize="1024" BlockYSize="1024" /> <SrcRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <DstRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <NODATA>0</NODATA> </ComplexSource> </VRTRasterBand> <VRTRasterBand dataType="UInt16" band="3"> <NoDataValue>0</NoDataValue> <ComplexSource> <SourceFilename relativeToVRT="0">/vsicurl/https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B02.tif</SourceFilename> <SourceBand>1</SourceBand> <SourceProperties RasterXSize="10980" RasterYSize="10980" DataType="UInt16" BlockXSize="1024" BlockYSize="1024" /> <SrcRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <DstRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <NODATA>0</NODATA> </ComplexSource> </VRTRasterBand> <VRTRasterBand dataType="UInt16" band="4"> <NoDataValue>0</NoDataValue> <ComplexSource> <SourceFilename relativeToVRT="0">/vsicurl/https://sentinel-cogs.s3.us-west-2.amazonaws.com/sentinel-s2-l2a-cogs/21/J/XN/2021/2/S2B_21JXN_20210214_1_L2A/B08.tif</SourceFilename> <SourceBand>1</SourceBand> <SourceProperties RasterXSize="10980" RasterYSize="10980" DataType="UInt16" BlockXSize="1024" BlockYSize="1024" /> <SrcRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <DstRect xOff="0" yOff="0" xSize="10980" ySize="10980" /> <NODATA>0</NODATA> </ComplexSource> </VRTRasterBand></VRTDataset>'
# Mpre configs (using VRT)
available_layers.update(
{
"true_color": {
"url": vrt_rdbnir,
"indexes": [1, 2, 3],
"render": {
"rescale": [
(0, 3000),
(0, 3000),
(0, 3000),
],
},
},
"false_color": {
"url": vrt_rdbnir,
"indexes": [4, 1, 2],
"render": {
"rescale": [
(0, 4000),
(0, 3000),
(0, 3000),
],
},
},
"ndvi": {
"url": vrt_rdbnir,
"expression": "(b4-b1)/(b4+b1)",
"render": {
"rescale": [
(-1, 1),
],
"colormap_name": "viridis",
},
},
}
)
# List of all Layers
layers_list = Literal["red", "green", "blue", "true_color", "false_color", "ndvi"]
# Custom `DatasetPathParams` which return the dataset URL for a `layer_id`
def DatasetPathParams(layer_id: layers_list = Path()) -> str:
return available_layers[layer_id]["url"]
@dataclass
class CustomAsDict:
"""Custom `DefaultDependency` to ignore `requests`"""
def as_dict(self, exclude_none: bool = True) -> Dict:
"""Transform dataclass to dict."""
exclude_keys = {"request"}
if exclude_none:
return {
k: v
for k, v in self.__dict__.items()
if v is not None and k not in exclude_keys
}
return {k: v for k, v in self.__dict__.items() if k not in exclude_keys}
# Custom Layer Param
@dataclass
class LayerParams(CustomAsDict, dependencies.BidxExprParams):
request: Request = field(default=None)
def __post_init__(self):
if (layer := self.request.path_params.get("layer_id")) and not any(
[self.indexes, self.expression]
):
layer_params = available_layers[layer]
if indexes := layer_params.get("indexes"):
self.indexes = indexes
elif expr := layer_params.get("expression"):
self.expression = expr
# Custom Rendering Params
@dataclass
class RenderingParams(CustomAsDict, dependencies.ImageRenderingParams):
request: Request = field(default=None)
def __post_init__(self):
super().__post_init__()
if layer := self.request.path_params.get("layer_id"):
layer_params = available_layers[layer].get("render", {})
if not self.rescale and (rescale := layer_params.get("rescale")):
self.rescale = rescale
if not self.color_formula and (color_formula := layer_params.get("color_formula")):
self.color_formula = color_formula
if self.add_mask is not None and (add_mask := layer_params.get("add_mask")):
self.add_mask = add_mask
# Custom ColorMap Params
def ColorMapParams(
request: Request,
colormap_name: Annotated[ # type: ignore
Literal[tuple(default_cmap.list())],
Query(description="Colormap name"),
] = None,
colormap: Annotated[
Optional[str], Query(description="JSON encoded custom Colormap")
] = None,
):
if layer := request.path_params.get("layer_id"):
layer_params = available_layers[layer].get("render", {})
colormap_name = layer_params.get("colormap_name", colormap_name)
colormap = layer_params.get("colormap", colormap)
if colormap_name:
return default_cmap.get(colormap_name)
if colormap:
try:
c = json.loads(
colormap,
object_hook=lambda x: {
int(k): parse_color(v) for k, v in x.items()
},
)
# Make sure to match colormap type
if isinstance(c, Sequence):
c = [(tuple(inter), parse_color(v)) for (inter, v) in c]
return c
except json.JSONDecodeError as e:
raise HTTPException(
status_code=400, detail="Could not parse the colormap value."
) from e
return None
app = FastAPI()
cog = TilerFactory(
path_dependency=DatasetPathParams,
layer_dependency=LayerParams,
render_dependency=RenderingParams,
colormap_dependency=ColorMapParams,
router_prefix="/layers/{layer_id}",
)
app.include_router(cog.router, prefix="/layers/{layer_id}")
add_exception_handlers(app, DEFAULT_STATUS_CODES)
# Run the application
import uvicorn
uvicorn.run(app=app, host="127.0.0.1", port=8080, log_level="info")
http://127.0.0.1:8080/docs
http://127.0.0.1:8080/layers/ndvi/preview
