The issue you're experiencing with getting a black image could be due to several factors in implementation of the heat equation for image deblurring.
- Conductivity Coefficient k: In given code, “k” is being assigned the number of colour channels of the image. This is incorrect for image deblurring. Define “k” as a small positive constant that controls the rate of diffusion (e.g., k = 0.1).
- Ensure that the pixel values remain within a valid range (0 to 255) during the iterations. If the values exceed this range, they might cause the image to appear completely black or white.
- When using “imagesc”, the scaling might affect the display. Ensure that the image data is correctly scaled for visualization.
Revised code with above mentioned consideration will be:
% Read and preprocess the image
u0=imread(‘path_to_your_image.jpeg');
% Convert to grayscale if the image is in color
if size(u0, 3) == 3
u0 = rgb2gray(u0);
end
% Convert to double for processing
u0 = double(u0);
% Get the dimensions of the image
[m, n] = size(u0);
% Display the original image
figure;
subplot(1,2,1);
imagesc(u0);
colormap gray;
title('Original');
% Parameters for the heat equation
dt = 0.02; % Time step
T = 100; % Stopping time
k = 0.1; % Conductivity coefficient a small positive constant
% Initialize the image for processing
u = u0;
% Iterative deblurring using the heat equation
for t = 0:dt:T
% Compute second derivatives
u_xx = u(:, [2:n n]) - 2*u + u(:, [1 1:n-1]);
u_yy = u([2:m m], :) - 2*u + u([1 1:m-1], :);
% Update the image
u = u + k*dt*(u_xx + u_yy);
% Clip values to ensure they are within valid range
u = max(min(u, 255), 0);
% Display the updated image
subplot(1,2,2);
imagesc(u, [0 255]); % Ensure the display range is set
colormap gray;
title(['t = ', num2str(t)]);
drawnow;
end
% Save the final deblurred image
imwrite(uint8(u), 'clockdeblur.tiff', 'TIFF');
The output for the following code with sample input is given below:
For better understanding of “imagesc”, refer to the documentation, which you can access by running the following command in MATLAB command window:
- web(fullfile(docroot, "matlab/ref/imagesc.html"))
Hope that helps!
