imhist (Image Processing Toolbox User's Guide)

Image Processing Toolbox User's Guide

Display histogram of image data

Syntax

imhist(I,n)
imhist(X,map)
[counts,x] = imhist(...)

Description

imhist(I) displays a histogram for the intensity image I above a grayscale colorbar. The number of bins in the histogram is specified by the image type. If I is a grayscale image, imhist uses a default value of 256 bins. If I is a binary image, imhist uses 2 bins.

imhist(I,n) displays a histogram where n specifies the number of bins used in the histogram. n also specifies the length of the colorbar. If I is a binary image, n can only have the value 2.

imhist(X,map) displays a histogram for the indexed image X. This histogram shows the distribution of pixel values above a colorbar of the colormap map. The colormap must be at least as long as the largest index in X. The histogram has one bin for each entry in the colormap.

[counts,x] = imhist(...) returns the histogram counts in counts and the bin locations in x so that stem(x,counts) shows the histogram. For indexed images, it returns the histogram counts for each colormap entry; the length of counts is the same as the length of the colormap.

Note For intensity images, the n bins of the histogram are each half-open intervals of width

. In particular, for intensity images that are not int16, the

th bin is the half-open interval

, where x is the intensity value. For int16 intensity images, the

th bin is the half-open interval

, where x is the intensity value. The scale factor

depends on the image class.

is 1 if the intensity image is double or single,

is 255 if the intensity image is uint8, and

is 65535 if the intensity image is uint16 or int16.

Class Support

An input intensity image can be of class uint8, uint16, int16, single, double, or logical. An input indexed image can be of class uint8, uint16, single, double, or logical.

Example

```
I = imread('pout.tif');
imhist(I)
```

See Also

histeq

hist in the MATLAB Function Reference

imhandles imhmax