1、图像加密
(1)异或的基本概念
函数: c = xor(a, b)
(2)按位异或
函数: c = bitxor(a, b)
%% 按位异或 a = 5; b = 4; c = bitxor(a,b);
(3)二值图像异或图像加密/解密
%% 二值图像按位异或 I = imread('lena.jpg'); I = im2bw(I); % 彩色图像转为二值图像 subplot(2,2,1),imshow(I),title('原始图像'); key = creatBI(0.98); subplot(2,2,2),imshow(key),title('密钥图像'); secret_image = bitxor(I,key); subplot(2,2,3),imshow(secret_image),title('加密图像'); recv_image = bitxor(secret_image,key); subplot(2,2,4),imshow(recv_image),title('解密图像');
(4)灰度图像异或加密/解密
%% 灰度图像按位异或 I = imread('lena.jpg'); I = rgb2gray(I); % 彩色图像转为灰度图像 subplot(2,2,1),imshow(I),title('原始图像'); key = grayImage(0.98); subplot(2,2,2),imshow(key),title('密钥图像'); secret_image = bitxor(I,key); subplot(2,2,3),imshow(secret_image),title('加密图像'); recv_image = bitxor(secret_image,key); subplot(2,2,4),imshow(recv_image),title('解密图像');
(5)彩色图像异或加密/解密
%% 彩色图像按位异或 I = imread('secret.png'); subplot(2,2,1),imshow(I),title('原始图像'); key = RgbImage(0.98,0.56,0.23); subplot(2,2,2),imshow(key),title('密钥图像'); secret_image = bitxor(I,key); subplot(2,2,3),imshow(secret_image),title('加密图像'); recv_image = bitxor(secret_image,key); subplot(2,2,4),imshow(recv_image),title('解密图像');
2、数组方式处理图像
(1)几何变换——自定义截取图像
%% 自定义截取子图像 I = imread('lena.jpg'); m = 100:300; n = 100:300; J = I(m,n); subplot(1,2,1),imshow(I); subplot(1,2,2),imshow(J);
(2)几何变换——移动
新图像(X,Y) = 原图像(X+M, Y+N)
%% 移动 I = imread('lena.jpg'); I = rgb2gray(I); [m,n] = size(I); x = 201:m; y = 101:n; new = zeros(m,n); new(x,y) = I(x-200,y-100); subplot(1,2,1),imshow(I,[]); subplot(1,2,2),imshow(new,[]);
(3)自定义均值去噪
%% 自定义均值去噪函数调用 I = imread('lena.jpg'); I = rgb2gray(I); % 彩色图像转换为灰度图像 J = imnoise(I,'salt & pepper'); subplot(1,2,1),imshow(J,[]); [m,n] = size(J); x = 2:m-1; y = 2:n-1; new = zeros(m,n); o = double(J); new(x,y) = (o(x-1,y)+o(x-1,y-1)+o(x-1,y+1)+o(x+1,y)+... o(x+1,y+1)+o(x+1,y-1)+o(x,y+1)+o(x,y-1))/8; subplot(1,2,2),imshow(new,[]);
(4)自定义二值化去噪
符合要求的下标 = find(条件)
%% 自定义二值化去噪 I = imread('lena.jpg'); I = rgb2gray(I); % 彩色图像转换为灰度图像 subplot(1,2,1),imshow(I,[]); [m,n] = size(I); new = zeros(m,n); index = find(I>128); new(index) = 255; subplot(1,2,2),imshow(new,[]);
(5)自定义获取边缘
%% 自定义获取边缘 I = imread('cameraman.tif'); subplot(1,2,1),imshow(I,[]); [m,n] = size(I); x = 2:m-1; y = 2:n-1; key = 20; % 阈值 index = find(abs(I(x,y)-I(x-1,y))>key... | abs(I(x,y)-I(x,y-1))>key... | abs(I(x,y)-I(x+1,y))>key... |abs(I(x,y)-I(x,y+1))>key); edge = ones(m-2,n-2); edge(index) = 0; subplot(1,2,2),imshow(edge,[]);
3、图像置乱
(1)置乱序列的生成
① 生成数据序列:混沌系统
② 生成置乱序列:
%% 置乱序列的生成 clc; clear all; x = linspace(0,0,20); x(1) = 0.98; for i = 2:20 x(i) = 1-2*x(i-1)*x(i-1); end [a,b] = sort(x); % 生成置乱序列
(2)置乱序列的编码实现
%% 置乱序列的编码实现 clc; clear all; a = linspace(55,64,10); c = linspace(0,0,10); c(1) = 0.56; for i = 2:10 c(i) = 1-2*c(i-1)*c(i-1); end [cI,b] = sort(c); i = 1:10; ax(i) = a(b(i)); % b(i)是乱序序列,置乱 ay(b(i)) = ax(i); % 还原
(3)图像置乱
%% 图像置乱 a = imread('lena.jpg'); % a = im2bw(a); % 转成二值图像 [m,n] = size(a); x = linspace(0,0,m*n); x(1) = 0.23; for i=2:m*n x(i) = 1-2*x(i-1)*x(i-1); end [xs,xIndex] = sort(x); i = 1:m*n; aSecret = a; % 设置初始大小 aDe = a; % 设置初始大小 aSecret(i) = a(xIndex(i)); aDe(xIndex(i)) = aSecret(i); subplot(1,3,1),imshow(a);title('原始图像'); subplot(1,3,2),imshow(aSecret);title('置乱图像'); subplot(1,3,3),imshow(aDe);title('逆置乱图像');