MAINT: more memory efficient multichannel implementation
MAINT: more memory efficient multichannel implementation

also make multichannel default to False to match other denoising routines

ofgulban/scikit-image,rjeli/scikit-image,vighneshbirodkar/scikit-image,rjeli/scikit-image,vighneshbirodkar/scikit-image,paalge/scikit-image,ofgulban/scikit-image,rjeli/scikit-image,paalge/scikit-image,paalge/scikit-image,ofgulban/scikit-image,vighneshbirodkar/scikit-image