How to handle division by zero (inf/nan) edge cases in statistics endpoint

[dimplejaiin]

When using the /stac/statistics endpoint with expressions that can produce division by zero (resulting in inf or nan values), the endpoint returns a 500 error with "index out of bounds" during histogram computation.

Simple Example

Expression: (B06 - B05) / (B06 + B05)

If pixel has: B06 = 50, B05 = -50
Then: (50 - (-50)) / (50 + (-50)) = 100/0 = infinity

When any pixel results in infinity, TiTiler crashes while computing histogram.

Steps to Reproduce

1. Use an expression with potential division by zero:
   expression=705 + 35 * ((B04 + B07)/2 - B05) / (B06 - B05)

2. When some pixels have B06 == B05, the denominator becomes zero, producing inf values.

3. Request:
   GET /stac/statistics?url=&expression=&histogram_bins=5&asset_as_band=true

4. Response:

{
  "detail": "index -9223372036854775808 is out of bounds for axis 0 with size 6"
}

Expected Behavior

Similar to how QGIS/GDAL handles this:

• Pixels with division by zero should be treated as nodata and excluded from statistics
• min, max, mean, histogram should only consider valid (finite) values
• Percentiles should be computed from valid values only

Request for Guidance

Could you please advise if there is an existing solution for this, or would any of these approaches be feasible?

1. Automatically mask inf/nan values before computing statistics
2. Add an optional parameter like mask_inf=true
3. Use a custom algorithm extension

Thank you for your time and support! @vincentsarago

[vincentsarago]

@dimplejaiin could you share a minimal reproducible example with data please 🙏

[dimplejaiin]

I’m unable to share the private STAC URL, so reproducing the issue using /cog/statistics with a local COG.

Reproduction Steps

curl -X 'GET' \
  'http://127.0.0.1:8000/cog/statistics?url=test_merged_reip.tif&expression=705%2B35%2A%28%28b1%2Bb4%29%2F2-b2%29%2F%28b3-b2%29&max_size=1024' \
  -H 'accept: application/json'

TIF file used: here
Expression: 705+35*((b1+b4)/2-b2)/(b3-b2)

Traceback

INFO:     127.0.0.1:60259 - "GET /cog/statistics?url=%2FUsers%2Fdimple%2FDownloads%2Ftest_merged_reip.tif&expression=705%2B35%2A%28%28b1%2Bb4%29%2F2-b2%29%2F%28b3-b2%29%2B0.0001&max_size=1024 HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/uvicorn/protocols/http/httptools_impl.py", line 419, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/applications.py", line 1134, in __call__
    await super().__call__(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/applications.py", line 107, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/cors.py", line 87, in __call__
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/middleware/asyncexitstack.py", line 18, in __call__
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    await route.handle(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 290, in handle
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 119, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 105, in app
    response = await f(request)
               ^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 424, in app
    raw_response = await run_endpoint_function(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 314, in run_endpoint_function
    return await run_in_threadpool(dependant.call, **values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/concurrency.py", line 32, in run_in_threadpool
    return await anyio.to_thread.run_sync(func)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/to_thread.py", line 61, in run_sync
    return await get_async_backend().run_sync_in_worker_thread(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 2525, in run_sync_in_worker_thread
    return await future
           ^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 986, in run
    result = context.run(func, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/titiler/core/factory.py", line 484, in statistics
    return image.statistics(
           ^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/rio_tiler/models.py", line 910, in statistics
    stats = get_array_statistics(
            ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/rio_tiler/utils.py", line 174, in get_array_statistics
    h_counts, h_keys = numpy.histogram(data_comp, **kwargs)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/numpy/lib/_histograms_impl.py", line 792, in histogram
    bin_edges, uniform_bins = _get_bin_edges(a, bins, range, weights)
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/numpy/lib/_histograms_impl.py", line 449, in _get_bin_edges
    raise ValueError(
ValueError: Too many bins for data range. Cannot create 10 finite-sized bins.
INFO:     127.0.0.1:60346 - "GET /cog/statistics?url=%2FUsers%2Fdimple%2FDownloads%2Ftest_merged_reip.tif&expression=705%2B35%2A%28%28b1%2Bb4%29%2F2-b2%29%2F%28b3-b2%29%2B0.000001&max_size=1024 HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/uvicorn/protocols/http/httptools_impl.py", line 419, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/applications.py", line 1134, in __call__
    await super().__call__(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/applications.py", line 107, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/cors.py", line 87, in __call__
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/middleware/asyncexitstack.py", line 18, in __call__
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    await route.handle(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 290, in handle
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 119, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 105, in app
    response = await f(request)
               ^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 424, in app
    raw_response = await run_endpoint_function(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 314, in run_endpoint_function
    return await run_in_threadpool(dependant.call, **values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/concurrency.py", line 32, in run_in_threadpool
    return await anyio.to_thread.run_sync(func)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/to_thread.py", line 61, in run_sync
    return await get_async_backend().run_sync_in_worker_thread(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 2525, in run_sync_in_worker_thread
    return await future
           ^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 986, in run
    result = context.run(func, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/titiler/core/factory.py", line 484, in statistics
    return image.statistics(
           ^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/rio_tiler/models.py", line 910, in statistics
    stats = get_array_statistics(
            ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/rio_tiler/utils.py", line 174, in get_array_statistics
    h_counts, h_keys = numpy.histogram(data_comp, **kwargs)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/numpy/lib/_histograms_impl.py", line 792, in histogram
    bin_edges, uniform_bins = _get_bin_edges(a, bins, range, weights)
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/numpy/lib/_histograms_impl.py", line 449, in _get_bin_edges
    raise ValueError(
ValueError: Too many bins for data range. Cannot create 10 finite-sized bins.
INFO:     127.0.0.1:60459 - "GET /cog/statistics?url=%2FUsers%2Fdimple%2FDownloads%2Ftest_merged_reip.tif&expression=705%2B35%2A%28%28b1%2Bb4%29%2F2-b2%29%2F%28b3-b2%29&max_size=1024 HTTP/1.1" 500 Internal Server Error
ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/uvicorn/protocols/http/httptools_impl.py", line 419, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/applications.py", line 1134, in __call__
    await super().__call__(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/applications.py", line 107, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/errors.py", line 186, in __call__
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/errors.py", line 164, in __call__
    await self.app(scope, receive, _send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/cors.py", line 87, in __call__
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/middleware/exceptions.py", line 63, in __call__
    await wrap_app_handling_exceptions(self.app, conn)(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/middleware/asyncexitstack.py", line 18, in __call__
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 716, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 736, in app
    await route.handle(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/routing.py", line 290, in handle
    await self.app(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 119, in app
    await wrap_app_handling_exceptions(app, request)(scope, receive, send)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 53, in wrapped_app
    raise exc
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/_exception_handler.py", line 42, in wrapped_app
    await app(scope, receive, sender)
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 105, in app
    response = await f(request)
               ^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 424, in app
    raw_response = await run_endpoint_function(
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/fastapi/routing.py", line 314, in run_endpoint_function
    return await run_in_threadpool(dependant.call, **values)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/starlette/concurrency.py", line 32, in run_in_threadpool
    return await anyio.to_thread.run_sync(func)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/to_thread.py", line 61, in run_sync
    return await get_async_backend().run_sync_in_worker_thread(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 2525, in run_sync_in_worker_thread
    return await future
           ^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 986, in run
    result = context.run(func, *args)
             ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/titiler/core/factory.py", line 484, in statistics
    return image.statistics(
           ^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/rio_tiler/models.py", line 910, in statistics
    stats = get_array_statistics(
            ^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/rio_tiler/utils.py", line 174, in get_array_statistics
    h_counts, h_keys = numpy.histogram(data_comp, **kwargs)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/numpy/lib/_histograms_impl.py", line 792, in histogram
    bin_edges, uniform_bins = _get_bin_edges(a, bins, range, weights)
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/dimple/Desktop/Titiler/titiler/lib/python3.12/site-packages/numpy/lib/_histograms_impl.py", line 449, in _get_bin_edges
    raise ValueError(
ValueError: Too many bins for data range. Cannot create 10 finite-sized bins.

Observation

The error appears during histogram generation inside numpy.histogram.
It seems the expression occasionally produces extreme values (likely due to division by zero or near-zero denominator), which results in a degenerate or invalid data range for histogram binning.

Workaround

Modifying the expression to include a small epsilon in the denominator resolves the issue:

705+35*((b1+b4)/2-b2)/(b3-b2 + 0.00001)

• Is there a recommended way to handle this at the TiTiler level?

Thank You!