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BUG: Fix LabelMapMaskImageFilter BackgroundValue cast through label type - #2629
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BackgroundValue was cast to the LabelMap pixel type (unsigned) instead of the feature image type, silently destroying negative values. Fix by adding output_image_type: InputImageType2 to the yaml. Adds a C++ regression test. Fixes SimpleITK#2625 (S16)
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Summary
Fixes issue #2625 (S16):
BackgroundValueinLabelMapMaskImageFilterwas silently losing negative values due to a wrong cast.Root Cause
BackgroundValuewas declaredpixeltype: Output, but nooutput_image_typewas set in the YAML. The dual template's fallback assignsOutputImageType = InputImageType— the LabelMap type (unsigned integer). This caused thedoublebackground value to bestatic_castto the unsigned label pixel type before being forwarded to ITK, destroying any negative or non-integer value.Fix
Add
output_image_type: InputImageType2toLabelMapMaskImageFilter.yaml, makingOutputImageTypealias the feature image type as ITK's filter intends.Test
Added
BasicFilters.LabelMapMaskImageFilter_BackgroundValuePreservedinsitkBasicFiltersTests.cxx: runs the filter with a float feature image andBackgroundValue = -1000.0, asserts the output minimum is-1000.0.