kirsch_dir (Operator)

Name

kirsch_dir — Detect edges (amplitude and direction) using the Kirsch operator.

Synopsis

kirsch_dir(Image : ImageEdgeAmp, ImageEdgeDir : : )

Description

kirsch_dir calculates an approximation of the first derivative of the image data and is used as an edge detector. The filter is based on the following filter masks:

      -3  -3   5       -3   5   5      5   5   5       5   5  -3
      -3   0   5       -3   0   5     -3   0  -3       5   0  -3
      -3  -3   5       -3  -3  -3     -3  -3  -3      -3  -3  -3

       5  -3  -3       -3  -3  -3     -3  -3  -3      -3  -3  -3
       5   0  -3        5   0  -3     -3   0  -3      -3   0   5
       5  -3  -3        5   5  -3      5   5   5      -3   5   5

The result image contains the maximum response of all masks. The edge directions are returned in ImageEdgeDir, and are stored as x / 2. They correspond to the direction of the mask yielding the maximum response.

Parameters

Image (input_object)	(multichannel-)image(-array) → object (byte / int2 / uint2)
Input image.

ImageEdgeAmp (output_object)	(multichannel-)image(-array) → object (byte / int2 / uint2)
Edge amplitude (gradient magnitude) image.

ImageEdgeDir (output_object)	(multichannel-)image(-array) → object (direction)
Edge direction image.

Example

read_image(Image,'fabrik')
kirsch_dir(Image,Kirsch_dirA,Kirsch_dirD)
threshold(Kirsch_dirA,Res,128,255)

Result

kirsch_dir always returns 2 (H_MSG_TRUE). If the input is empty the behaviour can be set via set_system('no_object_result',<Result>). If necessary, an exception is raised.

Parallelization Information

kirsch_dir is reentrant and automatically parallelized (on tuple level, channel level, domain level).

Possible Predecessors

binomial_filter, gauss_image, sigma_image, median_image, smooth_image

Possible Successors

hysteresis_threshold, threshold, gray_skeleton, nonmax_suppression_dir, close_edges, close_edges_length

Alternatives

edges_image, sobel_dir, robinson_dir, prewitt_dir, frei_dir

See also

bandpass_image, laplace_of_gauss

Module

Foundation