#### Operator index > By section > Histogram [src]

Histograms and look-up tables are 1xn or nx1 images, where n is less than 256 or less than 65536, corresponding to 8- and 16-bit unsigned int images. They are tagged with a `VipsInterpretation` of `VIPS_INTERPRETATION_HISTOGRAM` and usually displayed by user-interfaces such as nip2 as plots rather than images.

These functions can be broadly grouped as things to find or build histograms (`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 of utility operations.

A final group of operations build tone curves. These are useful in pre-press work for adjusting the appearance of images. They are designed for CIELAB images, but might be useful elsewhere.

## Functions

- `vips_maplut()`
- `vips_percent()`
- `vips_stdif()`
- `vips_hist_cum()`
- `vips_hist_norm()`
- `vips_hist_equal()`
- `vips_hist_plot()`
- `vips_hist_match()`
- `vips_hist_local()`
- `vips_hist_ismonotonic()`
- `vips_hist_entropy()`
- `vips_case()`