This function filters the input image using a low-pass filter, with the specified parameters.
Declaration:
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AT_ERRCOUNT ACCUAPI IG_FIP_filter_lowpass(
HIGEAR hIGear,
const LPAT_RECT lpRect,
const AT_MODE nFilterBrand,
const AT_DOUBLE dCutoffFreq,
const AT_INT nFilterOrder,
const AT_DOUBLE dRippleFactor
);
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Arguments:
| Name | Type | Description |
| hIGear | HIGEAR | Handle of the input image, also pass out filtered image. |
| lpRect | const LPAT_RECT | Far pointer to an AT_RECT structure specifying the rectangular portion of the image on which to operate. If NULL, this operation will be performed on the entire image. |
| nFilterBrand | const AT_MODE | Brand of the filter to use. Constants IG_FREQIP_FILTER_BRAND_* are listed in file i_FreqIP.h. |
| dCutoffFreq | const AT_DOUBLE | Cutoff frequency for the low-pass filter. |
| nFilterOrder | const AT_INT | Filter order to use, applicable to all except Ideal filter. |
| dRippleFactor | const AT_DOUBLE | A factor which determines the pass-band ripple for Chebyshev filters, with value between [0, 1]. |
Return Value:
Returns the number of ImageGear errors that occurred during this function call.
Supported Raster Image Formats:
Grayscale - 8 bpp.
Sample:
FreqIP
Example:
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HIGEAR hIGear; /* Handle of the input image */
...
IG_FIP_filter_lowpass(hIGear, NULL, IG_FREQIP_FILTER_BRAND_GAUSSIAN, 0.3, 1, 0.5);
...
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Remarks:
Parameter nFilterBrand specifies the brand of filter to use, with available brands being Ideal, Butterworth, Gaussian, Chebyshev I, and Chebyshev II.
Parameter dCutoffFreq specifies the cutoff frequency for the low-pass filter. This parameter should have value within the range of [0, 1], where 0 is DC and 1 is the Nyquist frequency.