Various fixes for ViSP Canny implementation #2239

Job	Run time
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-9, /usr/bin/g++-9, 98)	8m 22s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-9, /usr/bin/g++-9, 11)	25m 48s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-9, /usr/bin/g++-9, 17)	29m 52s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-10, /usr/bin/g++-10, 98)	7m 39s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-10, /usr/bin/g++-10, 11)	22m 57s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/gcc-10, /usr/bin/g++-10, 17)	26m 55s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/clang, /usr/bin/clang++, 98)	9m 30s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/clang, /usr/bin/clang++, 11)	30m 48s
build-ubuntu-dep-apt (ubuntu-20.04, /usr/bin/clang, /usr/bin/clang++, 17)	34m 33s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-9, /usr/bin/g++-9, 98)	6m 39s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-9, /usr/bin/g++-9, 11)	20m 12s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-9, /usr/bin/g++-9, 17)	25m 44s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-10, /usr/bin/g++-10, 98)	7m 48s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-10, /usr/bin/g++-10, 11)	22m 10s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/gcc-10, /usr/bin/g++-10, 17)	26m 57s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/clang, /usr/bin/clang++, 98)	9m 19s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/clang, /usr/bin/clang++, 11)	31m 19s
build-ubuntu-dep-apt (ubuntu-latest, /usr/bin/clang, /usr/bin/clang++, 17)	35m 28s
	6h 22m 0s

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