MATLAB分段線性變換函數

我已經生成了一個函數來對圖像應用分段線性變換。基於這個功能，我不確定它是否正確執行。有時整個圖像顯示爲白色，所有像素列爲255.其他時間顯示輸出圖像，但結果不同。由於結果不同，我相信我的功能存在問題。該函數的代碼是在這裏：MATLAB分段線性變換函數

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)

下面是我的一些測試結果：

enter image description here