Photoshop图像处理算法—自动对比度和自动色调(自动色阶)

1、原理部分

2、程序部分(matlab)

自动色调

clc;clear;close all;

img=imread('IMG_0950_cut.jpg');

Image=double(img)/255;

figure(1);

imshow(Image);

%%

R=Image(:,:,1);

G=Image(:,:,2);

B=Image(:,:,3);

percent=0.001;

%%

Image_out(:,:,1)=Auto_Tune(R, percent);

Image_out(:,:,2)=Auto_Tune(G, percent);

Image_out(:,:,3)=Auto_Tune(B, percent);

figure(2);

imshow(Image_out);

function I_out=Auto_Tune(I, percent)

%%% the tonal range of the input image is 0-1.

[row, col]=size(I);

%%%sort the input image value

I_sort=sort(I(:));

I_out=I;

%%% based on the clipping percentage,

%%% compute the upper and lower boundaries

if (percent==0)

I_min=min(I_sort)

I_max=max(I_sort)

else

I_min=I_sort(floor(row*col*percent))

I_max=I_sort(floor(row*col*(1-percent)))

end

for i=1:row

for j=1:col

if(I(i,j)

I_out(i,j)=0;

elseif(I(i,j)>I_max)

I_out(i,j)=1;

else

I_out(i,j)=(I(i,j)-I_min)/(I_max-I_min);

end

end

end

-----------------------------------------------------------------------------

自动对比度

%运行文件clc;clear;close all;

img=imread('lena.jpg');

Image=double(img)/255;

figure(1);

imshow(Image);

%%

R=Image(:,:,1);

G=Image(:,:,2);

B=Image(:,:,3);

percent=0.001;

%获得各个通道的最大最小值

[R_max,R_min] = findMaxMin(R,percent);

[G_max,G_min] = findMaxMin(G,percent);

[B_max,B_min] = findMaxMin(B,percent);

%求出统一的最大最小值

Max=max(max(R_max,G_max),B_max);

Min=min(min(R_min,G_min),B_min);

%%

Image_out(:,:,1)=Auto_Tune(R,Max,Min);

Image_out(:,:,2)=Auto_Tune(G,Max,Min);

Image_out(:,:,3)=Auto_Tune(B,Max,Min);

figure(2);

imshow(Image_out);

%求出各个通道的按照比例裁切的最大最小值

function [I_max,I_min] = findMaxMin(I,percent )

%%%sort the input image value

I_sort=sort(I(:));

[row, col]=size(I);

%%% based on the clipping percentage,

%%% compute the upper and lower boundaries

if (percent==0)

I_min=min(I_sort);

I_max=max(I_sort);

else

I_min=I_sort(floor(row*col*percent));

I_max=I_sort(floor(row*col*(1-percent)));

end

end

%根据统一的最大最小值进行变换

function I_out=Auto_Tune(I,Max,Min)

%%% the tonal range of the input image is 0-1.

[row, col]=size(I);

I_out=I;

for i=1:row

for j=1:col

if(I(i,j)

I_out(i,j)=0;

elseif(I(i,j)>Max)

I_out(i,j)=1;

else

I_out(i,j)=(I(i,j)-Min)/(Max-Min);

end

end

end

3、运行结果

图1 原图

图 2 自动对比度

图 3 自动色调

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