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1 | initial version |

This is a new overloaded member function since OpenCV 3.2. It means that you can provide an arbitrary gradient image such as the Scharr gradient to the `Canny`

edge detector using the `dx`

and `dy`

function parameters (initially it was only Sobel).

It doesn't even have to be a standard edge detector. For instance: if you only wanted to detect horizontal edges you could provide `dy`

as a set of `zeros`

and just provide `dx`

by running a gradient filter over the image.

2 | No.2 Revision |

This is a new overloaded member function since OpenCV 3.2. It means that you can provide an arbitrary gradient image such as the Scharr gradient to the `Canny`

edge detector using the `dx`

and `dy`

function parameters (initially it was only Sobel).

It doesn't even have to be a standard edge detector. For instance: if you only wanted to detect horizontal edges you could provide `dy`

as a set of `zeros`

and just provide `dx`

by running a gradient filter over the image. ~~ ~~

3 | No.3 Revision |

This is a new overloaded member function since OpenCV 3.2. It means that you can provide an arbitrary gradient image such as the Scharr gradient to the `Canny`

edge detector using the `dx`

and `dy`

function parameters (initially it was only Sobel).

It doesn't even have to be a standard edge detector. For instance: if you only wanted to detect horizontal edges you could provide `dy`

as a set of `zeros`

and just provide `dx`

by running ~~a ~~the appropriate gradient filter over the image.

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