topographic_sketch — Compute the topographic primal sketch of an image.
topographic_sketch computes the topographic primal sketch of the input image Image. This is done by approximating the image locally by a bicubic polynomial (“facet model”). It serves to calculate the first and second partial derivatives of the image, and thus to classify the image into 11 classes. These classes are coded in the output image Sketch as numbers from 1 to 11. The classes are as follows:
Peak 1 Pit 2 Ridge 3 Ravine 4 Saddle 5 Flat 6 Hillside Slope 7 Hillside Convex 8 Hillside Concave 9 Hillside Saddle 10 Hillside Inflection 11
In order to obtain the separate classes as regions, a threshold operation has to be applied to the result image with the appropriate thresholds.
Image for which the topographic primal sketch is to be computed.
Label image containing the 11 classes.
* To extract the Ridges from a Image read_image(Image,'sinus') topographic_sketch(Image,Sketch) threshold(Sketch,Ridges,3,3)
Let n be the number of pixels in the image. Then O(n) operations are performed.
topographic_sketch returns 2 (H_MSG_TRUE) if all parameters are correct. If the input is empty the behavior can be set via set_system('no_object_result',<Result>). If necessary, an exception is raised.
R. Haralick, L. Shapiro: “Computer and Robot Vision, Volume I”; Reading, Massachusetts, Addison-Wesley; 1992; Kapitel 8.13.