Histograms and look-up tables are 1xn or nx1 images, where n is less than256 or less than 65536, corresponding to 8- and 16-bit unsigned int images.They are tagged with aVipsInterpretation ofVIPS_INTERPRETATION_HISTOGRAM and usually displayed by user-interfacessuch as nip2 as plots rather than images.
These functions can be broadly grouped as things to find or buildhistograms (vips_hist_find(),vips_hist_find_indexed(),vips_hist_find_ndim(),vips_buildlut(),vips_identity()), operations that manipulate histograms in some way(vips_hist_cum(),vips_hist_norm()),operations to apply histograms (vips_maplut()), and a variety ofutility operations.
A final group of operations build tone curves. These are useful in pre-presswork for adjusting the appearance of images. They are designed forCIELAB images, but might be useful elsewhere.