Scalar Gradient

EasyImage::.GradientScalar computes the (scalar) gradient image derived from a given source image.

The scalar value derived from the gradient depends on the preset lookup-table image.

The gradient of a grayscale image corresponds to a vector, the components of which are the partial derivatives of the gray-level signal in the horizontal and vertical direction. A vector can be characterized by a direction and a length, corresponding to the gradient orientation, and the gradient magnitude.

This function generates a gradient direction or gradient magnitude map (gray-level image) from a given gray-level image.
For efficiency, a pre-computed lookup-table is used to define the desired transformation.
This lookup-table is stored as a standard EImageBW8/EImageBW16.
Use EasyImage::.ArgumentImage or EasyImage::.ModulusImage once before calling GradientScalar.