MATLAB分段线性变换函数

我已经生成了一个函数来对图像应用分段线性变换。基于这个功能，我不确定它是否正确执行。有时整个图像显示为白色，所有像素列为255.其他时间显示输出图像，但结果不同。由于结果不同，我相信我的功能存在问题。该函数的代码是在这里：MATLAB分段线性变换函数

function T = piecewise_transform(f,n,r1,s1,r2,s2,r3,s3) 

% breakpoints: (0,0),(r1,s2),(r2,s2),(r3,s3),((L-1),(L-1)) 

% to get alpha, beta, etc, don't suppress echoing (remove ;) 

% find the parameters of each line 

L = 2^n; 

% s = a*r+b 

a1 = ((s1-0)/(r1-0)); 
b1 = ((s1/r1)); 
a2 = ((s2-s1)/(r2-r1)); 
b2 = ((s1*r2)-(s2*r1)/(r2-r1)); 
a3 = ((s3-s2)/(r3-r2)); 
b3 = (((s3-s2)/(r3-r2))*(s2/r2)); 
a4 = (((L-1)-s3)/((L-1)-r3)); 
b4 = (((L-1)-s3)/((L-1)-r3)*(s3/r3)); 

% put all parameters in two vectors 

A = [a1,a2,a3,a4] 
B = [b1,b2,b3,b4] 

[row,col] = size(f); 
T = f; 

for i = 1:row 
    for j=1:col 

    % find which line to use 

    %line 1 
    if f(i,j) < r1 
     flag = 1; 
    end 

    % line 2 
    if f(i,j) > r1 && f(i,j)<r2 
     flag = 2; 
    end 

    % line 3 
    if f(i,j) > r2 && f(i,j)<r3 
     flag = 3; 
    end 

    % line 4 
    if f(i,j) > r3 && f(i,j)<(L-1) 
     flag = 4; 
    end 

    T(i,j) = (A(flag)*f(i,j) + B(flag)); 
    end 
end 

T = uint8(T); 

imshow(T)

下面是我的一些测试结果：

enter image description here