计算直方图算法

histogram.m

  function bars=histogram(I)
  %用==提取某个灰度的像素
  %并用sum计算个数
  tic
  bars=zeros(1,256);
  for value 0:255
        bars(value+1)=sum(value==I(:))
  end
  bars=bars./numel(I)
  toc

brightness.m

  close all;
  clear all;
  clc;
  I=imread('图片地址');
  %I=rgb2gray(I);彩色图片需要转为灰度图片
  bars=histogram(I);
  set(0,'defaultFigurePosition',[100 100 1000 500]);
  set(0,'defaultFigureCOlor',[1 1 1]);
  figure;
  subplot(121),imshow('I');
  subplot(122),bar(0:255,bars);