National Instruments IMAQ Vision for LabWindows TM /CVI - Manual (Page 29)

Chapter 2 Getting Measurement-Ready Images
© National Instruments Corporation 2-13 IMAQ Vision for LabWindows/CVI User Manual
attenuation increases. This operation preserves all of the zero
frequency information. Zero frequency information corresponds
to the DC component of the image or the average intensity of
the image in the spatial domain.
• Highpass attenuation—The amount of attenuation is inversely
proportional to the frequency information. At high frequencies,
there is little attenuation. As the frequencies decrease, the
attenuation increases. The zero frequency component is removed
entirely.
• Lowpass truncation—Frequency components above the ideal
cutoff frequency are removed, and the frequencies below it remain
unaltered.
• Highpass truncation—Frequency components above the ideal
cutoff frequency remain unaltered, and the frequencies below it
are removed.
3. To transform your image back to the spatial domain, use
imaqInverseFFT() .
Complex Image Operations
The imaqExtractComplexPlane() and
imaqReplaceComplexPlane() functions allow you to access, process,
and update independently the real and imaginary planes of a complex
image. You can also convert planes of a complex image to an array
and back with
imaqComplexPlaneToArray() and
imaqArrayToComplexPlane() .