GroupBy - Merge Image: Pixel type BitType not supported for merging.

[imagejan]

WTF? Why can't BitType images not be merged with the GroupBy node, but get merged just fine using the Merger node? This limitation seems unnecessary, and the special casing going on here is not very imglibby:

knip/org.knime.knip.base/src/org/knime/knip/base/data/aggregation/ImgMergeOperator.java

Lines 566 to 585 in f284f3d

	if (m_type instanceof ByteType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new ByteTypeHandler();
	} else if (m_type instanceof UnsignedByteType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new UnsignedByteTypeHandler();
	} else if (m_type instanceof UnsignedShortType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new UnsignedShortTypeHandler();
	} else if (m_type instanceof ShortType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new ShortTypeHandler();
	} else if (m_type instanceof IntType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new IntTypeHandler();
	} else if (m_type instanceof LongType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new LongTypeHandler();
	} else if (m_type instanceof FloatType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new FloatTypeHandler();
	} else if (m_type instanceof DoubleType) {
	m_typeHandler = (RealTypeHandler<T, A, ADA>)new DoubleTypeHandler();
	} else {
	throw new IllegalArgumentException(
	"Pixel type " + m_type.getClass().getSimpleName() + " not supported for merging.");
	}

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Example workflow to reproduce the issue:

BitType Merging.zip