topographic_sketchtopographic_sketchTopographicSketchTopographicSketchtopographic_sketch (Operator)

Name

topographic_sketchtopographic_sketchTopographicSketchTopographicSketchtopographic_sketch — Compute the topographic primal sketch of an image.

Signature

topographic_sketch(Image : Sketch : : )

Description

topographic_sketchtopographic_sketchTopographicSketchTopographicSketchTopographicSketchtopographic_sketch computes the topographic primal sketch of the input image ImageImageImageImageimageimage. 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 SketchSketchSketchSketchsketchsketch 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.

Attention

Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.

Execution Information

Multithreading type: reentrant (runs in parallel with non-exclusive operators).
Multithreading scope: global (may be called from any thread).
Automatically parallelized on tuple level.
Automatically parallelized on channel level.

Parameters

ImageImageImageImageimageimage (input_object) (multichannel-)image(-array) → object (byte)

Image for which the topographic primal sketch is to be computed.

SketchSketchSketchSketchsketchsketch (output_object) (multichannel-)image(-array) → object (byte)

Label image containing the 11 classes.

Example (HDevelop)

* To extract the Ridges from a Image
read_image(Image,'sinus')
topographic_sketch(Image,Sketch)
threshold(Sketch,Ridges,3,3)

Example (C)

/* To extract the Ridges from a Image */
read_image(&Image,"sinus");
topographic_sketch(Image,&Sketch);
threshold(Sketch,&Ridges,3.0,3.0);

Example (HDevelop)

* To extract the Ridges from a Image
read_image(Image,'sinus')
topographic_sketch(Image,Sketch)
threshold(Sketch,Ridges,3,3)

Example (HDevelop)

* To extract the Ridges from a Image
read_image(Image,'sinus')
topographic_sketch(Image,Sketch)
threshold(Sketch,Ridges,3,3)

Example (HDevelop)

* To extract the Ridges from a Image
read_image(Image,'sinus')
topographic_sketch(Image,Sketch)
threshold(Sketch,Ridges,3,3)

Complexity

Let n be the number of pixels in the image. Then O(n) operations are performed.

Result

topographic_sketchtopographic_sketchTopographicSketchTopographicSketchTopographicSketchtopographic_sketch returns TRUE if all parameters are correct. If the input is empty the behavior can be set via set_system('no_object_result',<Result>)set_system("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)SetSystem("no_object_result",<Result>)set_system("no_object_result",<Result>). If necessary, an exception is raised.

Possible Successors

thresholdthresholdThresholdThresholdThresholdthreshold

References

R. Haralick, L. Shapiro: “Computer and Robot Vision, Volume I”; Reading, Massachusetts, Addison-Wesley; 1992; Kapitel 8.13.

Module

Foundation

Operators