MATLAB中 histogram 和 imhist 的区别

matlab有两个生成直方图的库函数，分别是imhist和histogram，二者有何区别呢？

区别就是：

• imhist
  • 官方help：imhist(I) calculates the histogram for the intensity image I and displays a plot of the histogram. The number of bins in the histogram is determined by the image type.
  • 可见，imhist的NumBins值是由图像类型决定的。若图像为uint8类型，则bin的数量为256，即[0:1:255]。

• histogram（早期版本为hist，现在matlab已不建议使用hist了）

  • 官方help：
    histogram(X) creates a histogram plot of X. The histogram function uses an automatic binning algorithm that returns bins with a uniform width, chosen to cover the range of elements in X and reveal the underlying shape of the distribution. histogram displays the bins as rectangles such that the height of each rectangle indicates the number of elements in the bin.

  nbins — Number of bins
  　　   Number of bins, specified as a positive integer. If you do not specify nbins, then histogram automatically calculates how many bins to use based on the values in X.

  • 可见，histogram的NumBins值可以人为设定，在未指定该参数时，系统将基于图像的灰度分布自动计算NumBins的值。

例程：

 imgColor = imread('lena.jpg');
 imgGray = rgb2gray(imgColor);

 %% imhist
 figure('name', 'imhist'),
 imhist(imgGray);

 %% histogram
 figure('name', 'histogram auto'),
 % histogram函数自动计算NumBins值
 hist2 = histogram(imgGray);
 % Find the bin counts
 binCounts = hist2.Values;
 % Get bin number
 binNum = hist2.NumBins;

 %% histogram 指定NumBins值
 % Specify number of histogram bins
 figure('name', 'histogram256'),
 hist256 = histogram(imgGray, 256); % 等同于 imhist(imgGray)

由运行结果也可看出，histogram(imgGray, 256)与imhist(imgGray)，二者在最大bin的灰度累计值是一样的。

reference

• http://www.ilovematlab.cn/thread-13665-1-1.html