matlab 灰度变换

╰半橙微兮° 2021-06-24 14:36 508阅读 0赞

## **(1)线性变换:** ##

通过建立灰度映射来调整源图像的灰度。

k>1增强图像的对比度；k=1调节图像亮度，通过改变d值达到调节亮度目的；0

i = imread('theatre.jpg');
    i = im2double(rgb2gray(i));
    [m,n]=size(i);
    %增加对比度
    Fa = 1.25; Fb = 0;
    O = Fa.*i + Fb/255;
    figure(1), subplot(221), imshow(O);
    title('Fa = 1.25, Fb = 0, contrast increasing');
    figure(2),subplot(221), [H,x]=imhist(O, 64);
    stem(x, (H/m/n), '.');
    title('Fa = 1.25, Fb = 0, contrast increasing');
    %减小对比度
    Fa =0.5; Fb = 0;
    O = Fa.*i + Fb/255;
    figure(1), subplot(222),imshow(O);
    title('Fa = 0.5, Fb = 0, contrast decreasing');
    figure(2), subplot(222), [H,x] = imhist(O, 64);
    stem(x, (H/m/n), '.');
    title('Fa = 0.5, Fb = 0, contrast decreasing');
    %线性亮度增加
    Fa = 0.5; Fb = 50;
    O = Fa.*i + Fb/255;
    figure(1), subplot(223), imshow(O);
    title('Fa = 0.5, Fb = 50, brightness control');
    figure(2), subplot(223), [H,x]=imhist(O,64);
    stem(x, (H/m/n), '.');
    title('Fa = 0.5, Fb = 50, brightness control');
    %反相显示
    Fa = -1; Fb = 255;
    O = Fa.*i + Fb/255;
    figure(1), subplot(224), imshow(O);
    title('Fa = -1, Fb = 255, reversal processing');
    figure(2), subplot(224),[H,x]=imhist(O, 64);
    stem(x, (H/m/n), '.');
    title('Fa = -1, Fb = 255, reversal processing');

## **(2)对数变换：** ##

增强低灰度，减弱高灰度值。

i = imread('theatre.jpg');
    
    
    i = rgb2gray(i);
    i = double(i);
    
    out1 = log(1+i)/0.065;
    out2 = log(1+i)/0.035;
    out1(find(out1>255)) = 255;
    out2(find(out2>255)) = 255;
    out1 = uint8(out1);
    out2 = uint8(out2);

## **(3)幂次变换：** ##

次数小于1时，增强低灰度，减弱高灰度；次数大于1时增强高灰度，减弱低灰度。

i = rgb2gray(imread('theatre.jpg'));
    i = double(i);
    y1 = 255*(i/255).^2.5;
    y2 = 255*(i/255).^0.4;
    y1 = uint8(y1);
    y2 = uint8(y2);

## **(4) 指数变换：** ##

增强高灰度，减弱低灰度。

i = imread('theatre.jpg');
    i = rgb2gray(i);
    i = double(i);
    
    y1 = 1.5.^(i*0.070)-1;
    y2 = 1.5.^(i*0.050)-1;
    y1(find(y1>255)) = 255;
    y2(find(y2>255)) = 255;
    y1 = uint8(y1);
    y2 = uint8(y2);

## **(5)灰度拉伸：** ##

有时图像灰度集中在某小块区域，需要改变图像对比度。

i = imread('theatre.jpg');
    i = rgb2gray(i);
    L = imadjust(i,[ ],[50/255;150/255]);
    J = imadjust(L,[50/255;150/255 ],[20/255;230/255]);

## **(6)灰度均衡：** ##

i = rgb2gray(imread('theatre.jpg'));
    LC = imadjust(i,[ ],[50/255;150/255]);
    HE1 = histeq(LC);%均衡函数

## **(7)直方图规定化：** ##

实现局部的灰度均衡。

img = rgb2gray(imread('theatre.jpg'));
    img_ref = rgb2gray(imread('rpic.jpg'));%参考图，按照这个的的直方图进行规定化
    [hgram, x] = imhist(img_ref);
    J = histeq(img, hgram);