Skip to content

GradientFilter

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description

GradientFilter[image] gives the gradient magnitude Sqrt[dx^2 + dy^2], using the normalised Sobel derivatives of DerivativeFilter. The magnitude rather than |dx| + |dy| because it is ROTATION INVARIANT: an edge at 45 degrees reports the same strength as one at 0, where the absolute sum would report it sqrt(2) times stronger and so bias every downstream threshold by orientation. A colour image is reduced to luminance first and differentiated once, rather than differentiated per channel and combined by some arbitrary rule.

Examples (1)

Every input below was run against the current Mathilda build and its output recorded.

Basic Examples (1)

In[1]:= ImageData[GradientFilter[Image[{{0., 0., 1., 1.}, {0., 0., 1., 1.}}]]]
Out[1]= {{0.0, 0.5, 0.5, 0.0}, {0.0, 0.5, 0.5, 0.0}}

Implementation notes

Attributes: Protected.

References