mars-titiler/app.py

"""Titiler-based Mars tile server for MGS MOLA ClrShade global basemap"""

import math

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware
from pyproj import CRS
from morecantile import tms, TileMatrixSet
from rio_tiler.io import Reader

from titiler.core.factory import TilerFactory

# Mars SimpleCylindrical CRS (equidistant cylindrical projection in meters)
MARS_CRS = CRS.from_proj4(
    "+proj=eqc +lat_ts=0 +lat_0=0 +lon_0=0 +x_0=0 +y_0=0 "
    "+a=3396190 +b=3396190 +units=m +no_defs"
)

# Mars extent in equidistant cylindrical projection
# x = R × lon_rad, y = R × lat_rad
_R = 3396190
_MAX_X = _R * math.pi        # ≈ 10,669,442 m (corresponds to ±180°)
_MAX_Y = _R * math.pi / 2    # ≈  5,334,721 m (corresponds to ±90°)

# Custom TMS for Mars with matrix_scale=[2, 1] to match Cesium GeographicTilingScheme
MARS_TMS = TileMatrixSet.custom(
    crs=MARS_CRS,
    extent=(-_MAX_X, -_MAX_Y, _MAX_X, _MAX_Y),
    identifier="MarsCylindrical",
    matrix_scale=[2, 1],
)

# Register custom TMS
tms = tms.register({"MarsCylindrical": MARS_TMS})

# Create FastAPI app
app = FastAPI(
    title="Titiler Mars",
    description="Mars MGS MOLA Color-Shaded Relief global tile server powered by Titiler",
)

# Configure CORS
app.add_middleware(
    CORSMiddleware,
    allow_origins=[
        "http://digitalmars.com.cn",
        "https://digitalmars.com.cn",
    ],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# Create COG Tiler with Mars TMS support
cog = TilerFactory(
    reader=Reader,
    supported_tms=tms,
)

app.include_router(cog.router, tags=["Cloud Optimized GeoTIFF"])


@app.get("/", include_in_schema=False)
def landing():
    """Landing page."""
    return {
        "title": "Titiler Mars Tile Server",
        "description": "Mars MGS MOLA Color-Shaded Relief global tile server",
        "endpoints": {
            "tiles": "/tiles/MarsCylindrical/{z}/{x}/{y}?url=<data_url>",
            "tilejson": "/MarsCylindrical/tilejson.json?url=<data_url>",
            "info": "/info?url=<data_url>",
            "preview": "/preview.png?url=<data_url>&max_size=512",
            "docs": "/docs",
        },
    }