DiscreteFourierTransformation Method (ILEADRasterProcess)

Remarks

(Raster Pro and above toolkits) Computes the Discrete Fourier transform of an image or the Inverse Discrete Fourier transform as specified in the lFlags parameter.

This method converts the image from the time domain to the frequency domain and vice versa using the Discrete Fourier Transform algorithm. Use the FastFourierTransformation method to use a Fast Fourier Transform algorithm on a bitmap. Please note however, that this method does not impose the size restrictions (the width and height having to be powers of 2) that the Fast Fourier Transform function, FastFourierTransformation, imposes upon bitmaps.

The lMinHarmonicX, lMaxHarmonicX, lMinHarmonicY and lMaxHarmonicY properties specify the frequency range to be computed when DFT_DFT is set in lFlags. It specifies the frequency range that will be used in the image construction when DFT_IDFT is chosen.

Before using this method, you need to use the InitFourierTransformation method. When you are finished, you should free the allocated array by calling the FreeFourierTransformation method.

This method does not support 12 and 16-bit grayscale and 48 and 64-bit color images. If the image is 12 and 16-bit grayscale and 48 and 64-bit color, the function will not return an error.

This method does not work on regions. If a bitmap has a region the method ignores it and processes the entire bitmap.

This method does not support signed data images. It returns the error code ERROR_SIGNED_DATA_NOT_SUPPORTED if a signed data image is passed to this method.

See Also