IDL Wavelet Toolkit User's Guide

Chapter 3: Theory and Examples 53Figure 3-2: The Denoise Widget for the MRI Brain ScanNotice that you have retained 12.5% of the coefficients and have discarded 87.5%.The black regions of the “Wavelet Coeffs” plot shows the discarded coefficients. Thepercent difference between the original and filtered image is about 6%. Examiningthe filtered image, you will notice that much of the speckling around the outside isnow gone. In addition, some of the small-scale features and low-contrast regionswithin the image have been diminished. Finally, the dotted line on the CumulativePower graph indicates that although you are only retaining 12.5% of the informationyou are preserving almost 100% of the variance, or power.IDL Wavelet ToolkitDenoise