Histogram - Serabe/rinzelight GitHub Wiki

A histogram is just a frequency table. In rinzelight there are five kinds histograms: one for each channel and one by intensity. There are one more method histogram*, basis for the rest of them.

histogram* accepts two parameters: the image and a function. The function, given four parameters (red, green, blue and alpha) returns an index for the histogram: a number between 0 and (quantum-range). histogram uses intensity as the function (actually, an anonymous function wrapping the intensity macro). The other four methods (red-histogram, green-histogram, blue-histogram, alpha-histogram) use anonymous functions that return the correct channel.

No.

Histograms are pretty useful for knowing what is the lower or highest value for a pixel channel. For knowing these datum, there are ten methods: min-value and max-value, if you are dealing with intensity histograms; and x-min-value and x-max-value (being x a channel) if you are dealing with channel histograms.