How to apply Cumulative Density Function Formula?

Hi,

I am trying to implement a research paper using MATLAB. i have to to apply this three formula, respectively.

PDa = zeros(1,256);

for i=1:256
 PDa(i) = hCL(i) / (width*height); % width*height = total number of pixels
end

CDa = zeros(1,256);  %create CDa in formula
CDa(1) = PDa(1) ;
for i=2:256
     CDa(i) =  PDa(i) +  CDa(i-1);
end

value_after_enhancement =  zeros(1,256); 
for i=1:256
     value_after_enhancement(i) = 255 * CDa(i); 
end

But maximum value of CDa is 0.109. So, i see a dark image (maximum pixel value is 3) as a result. I couldn't understand where the problem is in my code. Can you help me, please?

[Jeff Miller]

If CDa is a cumulative density, then CDa(end) should equal 1 (i.e., the PDa values should sum to 1).

Since that is not happening, maybe the problem is with how hCL is computed. What is hCL?

[Mustafa Uysal]

Thanks for answer, here is my previous steps

modified_histogram = zeros(1,256); %apply formula
for i=1:256
   modified_histogram(i) = (((log( histogram_of_image(i)+alfa))^beta));
end 

for i=1:256
    if(modified_histogram(i)~=0)
        sum = sum + modified_histogram(i);
        cnt=cnt+1;
    end
end

tcl = sum/cnt;    

hCL = zeros(1,256);
for i=1:256
    if((modified_histogram(i))>=tcl)
     hCL(i) = tcl;    
    else 
     hCL(i) = (modified_histogram(i));   
   end
end

[Jeff Miller]

Sorry, I cannot understand what you are trying to compute.

[Mustafa Uysal]

Thank you for reply.

I am trying to implement an contrast enhancement algorithm using this paper: Research Paper