Detect edges (amplitude and direction) using the Kirsch operator.
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.
Image (input_object) |
image(-array) -> object : byte |
Input image. |
ImageEdgeAmp (output_object) |
image(-array) -> object : byte |
Edge amplitude (gradient magnitude) image. |
ImageEdgeDir (output_object) |
image(-array) -> object : direction |
Edge direction image. |
read_image(:Image:'fabrik':) > kirsch_dir(Image:Kirsch_dirA,Kirsch_dirD::) > threshold__(Kirsch_dirA:Res:128,255:).
kirsch_dir 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.
gauss__, sigma__, median, smooth__
hysteresis_threshold__, threshold__, grey_skeleton__, nonmax_suppression_dir, close_edges1, close_edges2
edges__, sobel_dir, robinson_dir, prewitt_dir, frei_dir