how can i calculate the value of Sigmoid Function for image in matlab ?

Answer 1

[Samayochita]

Hi Maryem,

To apply the Sigmoid function to an image:

• Read the image
• Convert the image to grayscale
• Convert the image to double precision (since pixel values are usually in uint8 format)
• Apply the sigmoid function
• Normalize the output (Optional: to bring values back to displayable range)

Here is an example code that I wrote:

% Parameters for the Sigmoid function
alpha = 100;    % Location parameter (adjust as needed)
beta = 50;     % Scale parameter (adjust as needed)
% Apply the Sigmoid function
sigmoid_img = 1 ./ (1 + exp(-(img_double - alpha) / beta));
% Scale back to 0-255 for display 
sigmoid_img = uint8(sigmoid_img * 255);
% Display results
figure;
subplot(1,2,1), imshow(img), title('Original Image');
subplot(1,2,2), imshow(sigmoid_img), title('Sigmoid Transformed Image');

Hope this helps!