Various fixes for ViSP Canny implementation #2249

Job	Run time
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-9, /usr/bin/g++-9, 98)	9m 7s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-9, /usr/bin/g++-9, 11)	37m 40s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-9, /usr/bin/g++-9, 17)	30m 42s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-10, /usr/bin/g++-10, 98)	7m 37s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-10, /usr/bin/g++-10, 11)	24m 48s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-10, /usr/bin/g++-10, 17)	27m 10s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/clang, /usr/bin/clang++, 98)	9m 18s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/clang, /usr/bin/clang++, 11)	30m 52s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/clang, /usr/bin/clang++, 17)	34m 27s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-9, /usr/bin/g++-9, 98)	6m 45s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-9, /usr/bin/g++-9, 11)	20m 29s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-9, /usr/bin/g++-9, 17)	30m 30s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-10, /usr/bin/g++-10, 98)	7m 28s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-10, /usr/bin/g++-10, 11)	22m 23s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-10, /usr/bin/g++-10, 17)	28m 22s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/clang, /usr/bin/clang++, 98)	9m 34s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/clang, /usr/bin/clang++, 11)	30m 48s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/clang, /usr/bin/clang++, 17)	35m 8s
	6h 43m 8s

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