Digital Image Processing Using Scilab Pdf May 2026

// Low-pass filter in frequency domain [m, n] = size(gray_img); cx = m/2; cy = n/2; radius = 30; H = zeros(m, n); for i = 1:m for j = 1:n if sqrt((i-cx)^2 + (j-cy)^2) <= radius H(i, j) = 1; end end end

// 3. Denoise with median filter img = medfilt2(img, [3 3]);

// Closing (dilation followed by erosion) closed = imclose(binary, se); 8.1 Simple Thresholding // Global threshold threshold = 120; segmented = gray_img > threshold; imshow(segmented); 8.2 Otsu’s Thresholding // Compute Otsu threshold automatically [level, intensity] = otsu_thresh(gray_img); bw_otsu = gray_img > level; 8.3 Connected Components Labeling [labeled_img, num_objects] = bwlabel(bw_otsu); disp("Number of objects detected: " + string(num_objects)); 9. Fourier Transform for Frequency Domain Processing // Compute FFT F = fft2(double(gray_img)); F_shifted = fftshift(F); // Magnitude spectrum magnitude = log(abs(F_shifted) + 1); imshow(magnitude, []); digital image processing using scilab pdf

// Threshold to create binary image binary = gray_img > 128; // Structuring element (disk of radius 3) se = [0 1 0; 1 1 1; 0 1 0];

// 4. Enhance contrast img = histeq(img); // Low-pass filter in frequency domain [m, n]

median_filtered = medfilt2(gray_img, [3 3]); // Create Gaussian kernel (approx) gaussian_kernel = [1 2 1; 2 4 2; 1 2 1] / 16; gaussian_filtered = imfilter(gray_img, gaussian_kernel); 6. Edge Detection 6.1 Sobel Operator // Sobel kernels sobel_x = [-1 0 1; -2 0 2; -1 0 1]; sobel_y = [-1 -2 -1; 0 0 0; 1 2 1]; Gx = imfilter(double(gray_img), sobel_x); Gy = imfilter(double(gray_img), sobel_y);

// 6. Threshold processed = edges > 50; imshow(processed); end Image Enhancement 4

// Get image dimensions (rows, cols, channels) size(img) gray_img = rgb2gray(img); imshow(gray_img); 3.3 Access and Modify Pixels // Access pixel at row 100, column 150 pixel = img(100, 150, :); // Set a region of interest to black img(50:100, 50:100, :) = 0; 4. Image Enhancement 4.1 Histogram Equalization Improves contrast by spreading intensity values.