FastFourierTransformation Method (ILEADRasterProcess)

Remarks

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

This method converts the image from the time domain to the frequency domain and vice versa using a Fast Fourier Transform algorithm. Fast Fourier Transform algorithms are a simplification of a Discrete Fourier Transform and require that the image dimensions must be power of two (i.e. 2, 4, 8, 16, 32…etc). The number of computations needed are reduced from 2N2 to 2N LgN. Use the DiscreteFourierTransformation to use a Discrete Fourier Transform algorithm on a bitmap. If you try to use this method with a bitmap with dimensions that are not a power of two, the method will return an ERROR_INV_PARAMETER error.

Before using this method, you must call 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 function does not work on regions. If a bitmap has a region the function 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