Image enhancement with wavelet-optimized whitening

Due to its physical nature, the solar corona exhibits large spatial variations of intensity that make it difficult simultaneously visualize features present at all levels and scales. Many general-purpose specialized filters have been proposed enhance coronal images. However, most them require ad hoc tweaking parameters produce subjectively good results. Our aim was develop a general purpose image enhancement technique would equally results, but based on an objective criterion. The underlying principle method is equalization, or whitening, power in {\it \`a trous} wavelet spectrum input scales locations. An edge-avoiding modification transform uses bilateral weighting by local variance planes used suppress undesirable halos otherwise produced discontinuities data. Results are presented for variety extreme ultraviolet (EUV) white light images corona. filter produces sharp contrasted output, without requiring manual adjustment parameters. Furthermore, built-in denoising scheme prevents explosion high-frequency noise typical other methods, smoothing statistically significant small-scale features. standard version algorithm about two times faster than widely multiscale Gaussian normalization (MGN). slower, provides significantly better results presence spikes edges. Comparisons with methods suggest whitening may correspond subjective criterion users when adjusting free