Generate a bandpass filter with sinusoidal shape.
gen_sin_bandpass generates a rotationally invariant bandpass filter with the response being a sinusoidal function in the frequency domain. The maximum of the sine is determined by Frequency, which is given as a fraction of the maximum (horizontal and vertical) frequency that can be represented in an image of size Width x Height, i.e., Frequency should lie between 0 and 1. 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. The filter is always zero for the DC term, rises with the sine function up to Frequency, and drops for higher frequencies accordingly. The range of the sine used is from 0 to pi. All other points are set to zero.
|
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 | |
|
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 | |
gen_sin_bandpass returns 2 (H_MSG_TRUE) if all parameters are correct. If necessary, an exception handling is raised.
gen_sin_bandpass is reentrant and processed without parallelization.
fft_image, fft_generic, rft_generic
fft_image_inv, gen_gauss_filter, gen_derivative_filter, gen_bandpass, gen_bandfilter, gen_highpass, gen_lowpass
Foundation
