Image Preprocessing

Certain preprocessing steps can make digital image correlation more robust to differences between a reference and current image — some in pixel intensity, others in how well an image's content suits an FFT-based technique such as phase correlation.

• Brightness and Contrast shift and stretch the pixel-intensity histogram, the two most basic differences a reference and current image can have.
• Windowing tapers an image's edges toward zero before a Fourier transform, reducing spectral leakage.