gen_std_bandpass

gen_std_bandpass ( : ImageFilter : Frequency, Sigma, Type, Norm, Mode, Width, Height : )

Generate a bandpass filter with Gaussian or sinusoidal shape.

gen_std_bandpass generates a rotationally invariant bandpass filter with the response being determined by the parameters Frequency and Sigma: Frequency determines the location of the maximum response with respect to the DC term, while Sigma determines the width of the frequency band that passes the filter. Frequency and Sigma are specified as a fraction of the maximum (horizontal and vertical) frequency that can be represented in an image of size Width x Height. Frequency should lie between 0 and 1. For Type = 'gauss', a Gaussian response is generated with Sigma being the standard deviation. For Type = 'sin', a sine function is generated with the maximum at Frequency and the extent Sigma. To achieve a maximum efficiency of the filtering operation, the parameter Norm can be used to specify the normalization factor of the filter. If fft_generic and Norm = 'n' is used the normalization in the FFT can be avoided. Mode can be used to determine where the DC term of the filter lies or whether the filter should be used in the real-valued FFT. If fft_generic is used, 'dc_edge' can be used to gain efficiency. If fft_image and fft_image_inv are used for filtering, Norm = 'none' and Mode = 'dc_center' must be used. If rft_generic is used, Mode = 'rft' must be used.

Parameters

`ImageFilter` (output_object)	image `->` object : real
Bandpass filter as image in the frequency domain.

`Frequency` (input_control)	real `->` real
Distance of the filter's maximum from the DC term.
Default value: 0.1
Suggested values: 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0
Restriction: `Frequency >= 0`

`Sigma` (input_control)	real `->` real
Bandwidth of the filter (standard deviation).
Default value: 0.01
Suggested values: 0.002, 0.005, 0.01, 0.02, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.7, 1.0
Restriction: `Sigma >= 0`

`Type` (input_control)	string `->` string
Filter type.
Default value: 'sin'
List of values: 'sin', 'gauss'

`Norm` (input_control)	string `->` string
Normalizing factor of the filter.
Default value: 'none'
List of values: 'none', 'n'

`Mode` (input_control)	string `->` string
Location of the DC term in the frequency domain.
Default value: 'dc_center'
List of values: 'dc_center', 'dc_edge', 'rft'

`Width` (input_control)	integer `->` integer
Width of the image (filter).
Default value: 512
List of values: 128, 160, 192, 256, 320, 384, 512, 640, 768, 1024, 2048, 4096, 8192

`Height` (input_control)	integer `->` integer
Height of the image (filter).
Default value: 512
List of values: 120, 128, 144, 240, 256, 288, 480, 512, 576, 1024, 2048, 4096, 8192

Result

gen_std_bandpass returns 2 (H_MSG_TRUE) if all parameters are correct. If necessary, an exception handling is raised.

Parallelization Information

gen_std_bandpass is reentrant and processed without parallelization.

Possible Predecessors

fft_image, fft_generic, rft_generic

Possible Successors

convol_fft

Alternatives

gen_sin_bandpass

Module

Foundation