Currently working through a video tutorial on Compression - no no, we're not talking about audio data compression technologies like mp3, but rather compression as a way to control the dynamic range of a signal.
In the audio world, compressors work by decreasing the input signal by a certain gain (multiplication factor) above a certain audio limit. So for say, we set our compressor to work at -10 db, sounds below -10db are not affected, but louder sounds like say -6db, are affected by the compressors. How much it is affected, is by a ratio control, e.g. 3:1.
In vfx and photography, one function I do use at times is a power function - basically it keeps the brightest and darkest or 0 to 1 values at where they are, but selectively gradually brighten or darken the values in between them.
A compressor type function would be an interesting kind of filter to apply to data of all sorts. If I do apply it out of work, I'll be sure to post again...