MATLAB中 histogram 和 imhist 的区别

Posted 2020-10-11 朝研行歌

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：

 1 imgColor = imread(\'lena.jpg\');
 2 imgGray = rgb2gray(imgColor);
 3 
 4 %% imhist
 5 figure(\'name\', \'imhist\'),
 6 imhist(imgGray);
 7 
 8 %% histogram
 9 figure(\'name\', \'histogram auto\'),
10 % histogram函数自动计算NumBins值
11 hist2 = histogram(imgGray);
12 % Find the bin counts
13 binCounts = hist2.Values;
14 % Get bin number
15 binNum = hist2.NumBins;
16 
17 %% histogram 指定NumBins值
18 % Specify number of histogram bins
19 figure(\'name\', \'histogram256\'),
20 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