Matlab two-dimensional histogram display (code)

Ordinary histograms count the number of grayscale occurrences of pixels in an image.

One of the dimensions of the two-dimensional histogram is an ordinary histogram, which counts the number of grayscale occurrences of pixels in the image.

Two-dimensional histogram, 1-dimensional is an ordinary histogram, 2-dimensional is a neighborhood mean histogram with a radius of 1:

clear all;
close all;
clc;

img=imread('lena.jpg');
[m n]=size(img);
r=1;    %邻域半径

imgn=zeros(m+2*r+1,n+2*r+1);
imgn(r+1:m+r,r+1:n+r)=img;

imgn(1:r,r+1:n+r)=img(1:r,1:n);                 %扩展上边界
imgn(1:m+r,n+r+1:n+2*r+1)=imgn(1:m+r,n:n+r);    %扩展右边界
imgn(m+r+1:m+2*r+1,r+1:n+2*r+1)=imgn(m:m+r,r+1:n+2*r+1);    %扩展下边界
imgn(1:m+2*r+1,1:r)=imgn(1:m+2*r+1,r+1:2*r);       %扩展左边界

Hist=zeros(256,256);
for i=1+r:r+m
    for j=1+r:r+n
        pix1=uint8(imgn(i,j));
        pix2=uint8(mean2(imgn(i-r:i+r,j-r:j+r)));
        Hist(pix1+1,pix2+1)=Hist(pix1+1,pix2+1)+1;
    end
end
mesh(double(Hist))

operation result