frei_amp

Herror ::frei_amp ( Hobject Image, Hobject *ImageEdgeAmp ) HImage HImage::FreiAmp ( void ) const HImageArray HImageArray::FreiAmp ( void ) const

Detect edges (amplitude) using the Frei-Chen operator.

::frei_amp 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:

  A =
         1       sqrt(2)        1
         0          0           0
        -1      -sqrt(2)       -1

  B =
         1          0          -1
       sqrt(2)      0       -sqrt(2) 
         1          0          -1

The result image contains the maximum response of the masks A and B.

Parameters

`Image` (input_object)	(multichannel-)image(-array) `->` Hobject: HImage(Array) ( byte / int2 )
Input image.

`ImageEdgeAmp` (output_object)	(multichannel-)image(-array) `->` Hobject : HImage(Array)* ( byte / int2 )
Edge amplitude (gradient magnitude) image.

Example

read_image(&Image,"fabrik");
frei_amp(Image,&Frei_amp);
threshold(Frei_amp,&Edges,128,255);

Result

::frei_amp always returns H_MSG_TRUE. If the input is empty the behaviour can be set via ::set_system('no_object_result',<Result>). If necessary, an exception handling is raised.

Possible Predecessors

::gauss_image, ::sigma_image, ::median_image, ::smooth_image

Alternatives

::sobel_amp, ::kirsch_amp, ::prewitt_amp, ::robinson_amp, ::roberts

Module

Image filters