Alpha Masks #209
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Alpha Masks #209
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... by the AccumulateProjectorFactory
combines sources using alpha-weighted average
and fix interpolator selection bug
RandomAccessibleSource and RandomAccessibleSource4D need special treatment because the underlying data is in (un-bounded) RandomAccessible. The mask should be 1 everywhere, which is not what AbstractSource.getInterpolatedMaskedSource would do.
mask is 1 everywhere (also outside of interval bounds, because interval is only needed for the navigation box overlay in BDV)
Everything except the inner loop over a single line is now in AbstractVolatileHierarchyProjector. It is extended by VolatileHierarchyProjector and MaskedVolatileHierarchyProjector. VolatileHierarchyProjector handles "normal" Volatile<T> (as before). MaskedVolatileHierarchyProjector handles Masked<Volatile<T>>.
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Of course this can be extended to support other types of masks besides "inside-1-outside-0". 
The API for this needs a bit more thought, so I will postpone it to a separate PR. |
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This pull request has been mentioned on Image.sc Forum. There might be relevant details there: https://forum.image.sc/t/fiji-friends-weekly-dev-update-thread/103718/111 |
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This PR adds alpha masks for
Sources.When accumulating multiple sources into a final picture, these can be used to determine whether a rendered pixel comes from inside the source interval (or outside, or which ratio). This can be used for example to do a weighted average of sources such that black background pixels are excluded from the average (but black foreground pixels are not).
There is a new "blend mode" toggle in the UI (new icon in the Display Modes side panel, shortcut "U") that switches between the default "sum" interpolation and the new alpha-weighted "average":
If you set up your own
AccumulateProjectorFactoryviaBdvOptions, this will show up as a third option ("custom") in the blend mode toggle. CustomAccumulateProjectorFactorycan override the defaultboolean requiresMaskedSources()method if they want to have the masked version of the individual sources rendered to then be able to work with the RGBA alpha values. (This is a bit more work, so a bit slower compared to rendering the sources without masks.)All existing sources just support this without any code change. The default implementations of the new
Source.getMaskedSource()andSource.getInterpolatedMaskedSource()methods add a constant 1 mask inside the image interval, then extend that with 0 mask outside.To make this work, the new
Masked<T>types and interpolators from imglib2-8.0.0 are used (see Class hierarchy and interpolation of Masked types (v2) #381).