robinson_amp ( Image : ImageEdgeAmp : : )

Detect edges (amplitude) using the Robinson operator.

robinson_amp calculates an approximation of the first derivative of the image data and is used as an edge detector. In robinson_amp the following four of the originally proposed eight 3x3 filter masks are convolved with the image. The other four masks are obtained by a multiplication by -1. All masks contain only the values 0,1,-1,2,-2. -1 0 1 2 1 0 -2 0 2 1 0 -1 -1 0 1 0 -1 -2 0 1 2 1 2 1 -1 0 1 0 0 0 -2 -1 0 -1 -2 -1 The result image contains the maximum response of all masks.


Parameters

Image (input_object)
image(-array) -> object : byte
Input image.

ImageEdgeAmp (output_object)
image(-array) -> object : byte
Edge amplitude (gradient magnitude) image.


Example
read_image(:Image:'fabrik':) >
robinson_amp(Image:Robinson_amp::) >
threshold__(Robinson_amp:Edges:128,255:).

Result

robinson_amp always returns TRUE. If the input is empty the behaviour can be set via set_system(::'no_object_result',<Result>:). If necessary, an exception is raised.


Possible Predecessors

gauss__, sigma__, median, smooth__


Alternatives

sobel_amp, frei_amp, prewitt_amp, robinson_amp, roberts__


See also

bandpass__, laplace_of_gauss



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