Suppress spurious libtiff warnings when decoding GeoTIFF files#52
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shreyaskommuri wants to merge 2 commits intoNVIDIA:mainfrom
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Suppress spurious libtiff warnings when decoding GeoTIFF files#52shreyaskommuri wants to merge 2 commits intoNVIDIA:mainfrom
shreyaskommuri wants to merge 2 commits intoNVIDIA:mainfrom
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GeoTIFF embeds geographic metadata using tags that libtiff does not recognise natively (ModelPixelScale 33550, ModelTiepoint 33922, ModelTransformation 34264, GeoKeyDirectory 34735, GeoDoubleParams 34736, GeoAsciiParams 34737, GDAL_METADATA 42112, GDAL_NODATA 42113). libtiff emits "Unknown field with tag X encountered" warnings for each one. The image data is decoded correctly; only the warnings pollute stderr. Install a custom TIFFWarningHandler (SuppressGeoTIFFTagWarnings) in error_handling.h that silently drops warnings for these eight known tags and forwards all other libtiff warnings to stderr unchanged. Call InstallGeoTIFFWarningFilter() — which uses std::call_once so the handler is registered exactly once per process — from libtiffExtensionCreate in libtiff_ext.cpp, which is the natural entry point for the libtiff extension. Add test_decode_tiff_geotiff to test/python/test_decode_tiff.py. The test helper _create_geotiff builds a valid TIFF from scratch using only struct (no third-party dependency), embedding all eight suppressed tags. The test decodes the synthetic file with CPU_ONLY and default backends and asserts correct pixel values. Fixes: NVIDIA/DALI#6114 Signed-off-by: shreyaskommuri <shreyaskommuri@gmail.com>
b"0\x00" is 2 bytes — since count*typesize (2) <= 4, TIFF requires the value to be stored inline in the IFD entry, not as a file offset. The IFD entry was incorrectly treating a file offset as the value. Use b"-9999\x00" (6 bytes) so the offset is spec-valid. Signed-off-by: shreyaskommuri <shreyaskommuri@gmail.com>
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Summary
GeoTIFF embeds geographic metadata using tags that libtiff does not recognise natively (ModelPixelScale 33550, ModelTiepoint 33922, ModelTransformation 34264, GeoKeyDirectory 34735, GeoDoubleParams 34736, GeoAsciiParams 34737, GDAL_METADATA 42112, GDAL_NODATA 42113). libtiff emits
TIFFReadDirectory: Warning, Unknown field with tag X encounteredfor each one on every decode. The image data is decoded correctly; only the warnings pollute stderr.TIFFWarningHandler(SuppressGeoTIFFTagWarnings) inextensions/libtiff/error_handling.hthat silently drops warnings for the eight known GeoTIFF/GDAL tags and forwards all other libtiff warnings to stderr unchanged. Guards against a nullmoduleargument (permitted by the libtiff contract).InstallGeoTIFFWarningFilter()— which usesstd::call_oncewith a function-localstaticin aninlinefunction, so theonce_flagis shared across all translation units and the handler is registered exactly once per process — fromlibtiffExtensionCreateinlibtiff_ext.cpp._create_geotifftest helper intest/python/test_decode_tiff.pythat builds a valid 4×4 GeoTIFF from scratch using onlystruct(no third-party dependency), embedding all eight suppressed tags. Addtest_decode_tiff_geotiffthat decodes the synthetic file withCPU_ONLYand default backends and asserts correct pixel values.Related
Ported from NVIDIA/DALI#6336 at the request of @jantonguirao — the fix belongs at the libtiff layer in nvImageCodec rather than in DALI's image decoder.
Closes NVIDIA/DALI#6114 (via nvImageCodec bump in DALI).
Type of Change
Test plan
_create_geotiffhelper produces a TIFF-spec-valid file (all 8 GeoTIFF tags, correct inline/offset layout, pixel data intact)test_decode_tiff_geotiffparametrized overCPU_ONLYand default backendspytest test/python/test_decode_tiff.py::test_decode_tiff_geotiffin CIAI Disclosure
Signed-off-by: shreyaskommuri shreyaskommuri@gmail.com