图像点线性运算

对原灰度图像每个像素点进行线性操作，aX+b=X_new

a=1，b=0时不变

b!=0时所有灰度值上/下移

a>1时对比度上升

0<a<1时对比度减小

a<0时暗区变亮，亮区变暗，图像求补

pic=imread('pic/coltogray/1.jpg');
gray_pic=rgb2gray(pic);

[x,y]=size(gray_pic);

new_pic1=zeros(x,y);
new_pic2=zeros(x,y);
new_pic3=zeros(x,y);
new_pic4=zeros(x,y);
max=0;
for i=1:x
  for j=1:y
    if max<gray_pic(i,j)
      max=gray_pic(i,j);
    end
    
    new_pic1(i,j)=gray_pic(i,j)+50;
    new_pic2(i,j)=gray_pic(i,j)*1.5;
    new_pic3(i,j)=gray_pic(i,j)*0.8;
    new_pic4(i,j)=255-gray_pic(i,j);
  end
end

new_pic1=uint8(new_pic1);
new_pic2=uint8(new_pic2);
new_pic3=uint8(new_pic3);
new_pic4=uint8(new_pic4);

figure(1);
imshow(gray_pic);

figure(2);
set(figure(2),'name','D*D+50','Numbertitle','off');
imshow(new_pic1);

figure(3);
set(figure(3),'name','D*1.5','Numbertitle','off');
imshow(new_pic2);

figure(4);
set(figure(4),'name','D*0.8','Numbertitle','off');
imshow(new_pic3);

figure(5);
set(figure(5),'name','D*(-1)+255','Numbertitle','off');
imshow(new_pic4);