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Gradient filters |
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GradientFilters
Applies gradient filters, as Sobel, Laplace and Canny, to the image to enhance edges.
Category: Image Processing
Properties: Filter, Aperture Size, X Derivative Order, Y Derivative Order, Low Threshold, High Threshold, Display Operation, InputImage, OutputImage.
Class: TVMGradientFilters
Description
Gradient filters are used for edge enhancement. They are also called edge detectors. This is an important feature for image processing as it helps to isolate objects present in the image.
The Sobel operator performs a 2-D spatial gradient measurement on both axes of an image and so emphasizes regions of high spatial frequency that correspond to edges.
The SobelXY operator is similar to Sobel but you can select the derivative order in both axes.
The Laplacian is a 2-D isotropic measure of the 2nd spatial derivative of an image. It highlights regions of rapid intensity change.
The Canny detector is a multi-steep algorithm. It produces a resulting image where only the maximal values of the edges found are shown.
Static Properties
Filter
Selects the gradient filter method to use. Available values are Sobel, SobelXY, Laplacian and Canny.
Aperture Size
Specifies the size of the kernel used by the filters. Big kernel sizes reduce noise effects. For Sobel and Laplacian operators available values are Scharr, 1, 3 and 7. For Canny operator only values of 3, 5 and 7 are valid. Scharr aperture corresponds to a special 3x3 kernel and aperture size 1 corresponds to a 3x1 or 1x3 kernel. Values of 3, 5 and 7 correspond to standard square kernel of the size of value.
X Derivative Order
Sets the order of the derivative used by the SobelXY operator on the horizontal axis. Its value should be lower than the aperture size and at least one of X Derivative Order or Y Derivative Order be greater than 0.
Y Derivative Order
Sets the order of the derivative used by the SobelXY operator on the vertical axis. Its value should be lower than the aperture size and at least one of X Derivative Order or Y Derivative Order be greater than 0.
Low Threshold
Used for Canny operator. Species the threshold for edge linking. If Low Threshold value is greater than High Threshold value, Low Threshold acquires the meaning of High Threshold and vice versa.
High Threshold
Used for Canny operator. Species the threshold to find initial segments of strong edges. If High Threshold value is less than Low Threshold value, High Threshold acquires the meaning of Low Threshold and vice versa.
Display Operation
Specifies whether or not to display the image resulting from the operation.
Dynamic Properties
Input Properties
InputImage
Holds the image or ROI to be processed by the operation. Must be a gray level image.
Output Properties
OutputImage
Holds the resulting image from the operation.
See also:
Sample |
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| Others in this Category | |
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Image Threshold |
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Morphological Operator |
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Image Adjustments |
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Convolution |
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Smoothing Filters |
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Image Arithmetics |
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