bandpass__ ( Image : ImageBandpass : FilterType : )

Edge extraction using bandpass filters.

bandpass__ serves as an edge filter. It applies a linear filter with the following convolution mask to Image:

FilterType: 'lines' In contrast to the edge operator sobel_amp this filter detects lines instead of edges, i.e., two closely adjacent edges. 0 -2 -2 -2 0 -2 0 3 0 -2 -2 3 12 3 -2 -2 0 3 0 -2 0 -2 -2 -2 0

At the border of the image the gray values are mirrored. Over- and underflows of gray values are clipped to the interval [0,255]. The resulting images are returned in ImageBandpass.


Parameters

Image (input_object)
image(-array) -> object : byte
Input images.

ImageBandpass (output_object)
image(-array) -> object : byte
Bandpass-filtered images.

FilterType (input_control)
string -> string
Filter type: currently only 'lines' is supported.
Default value: 'lines'
List of values: 'lines'


Example
bandpass__(Image,&LineImage,"lines");
threshold__(LineImage,&Lines,60.0,255.0);
skeleton(Lines,&ThinLines);

Result

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


Possible Successors

threshold__, skeleton


Alternatives

convol__, topographic_sketch, laws_byte


See also

highpass__, grey_skeleton__



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