How to extract patch of 4*4 size on the extracted SIFT features Keypoint (for eg: SIFT feature of an image 961*128)?

Extraction a patch size of 4*4 on the keypoints extracted from the SIFT feature extraction. example for an image I have got SIFT feature as 650*128.

Answer 1

[Gautam]

Hello Dheer,

You can modify the code below to extract patches from the SIFT Features key points

for i = 1:length(valid_points)
    % Get the position of the keypoint
    x = round(valid_points(i).Location(1));
    y = round(valid_points(i).Location(2));
    
    % Define the patch boundaries
    x_start = max(1, x - half_patch);
    x_end = min(size(img, 2), x + half_patch - 1);
    y_start = max(1, y - half_patch);
    y_end = min(size(img, 1), y + half_patch - 1);
    
    % Extract the patch
    patch = img(y_start:y_end, x_start:x_end);
    
    % Ensure the patch is 4x4 by padding if necessary
    if size(patch, 1) < patch_size || size(patch, 2) < patch_size
        patch = padarray(patch, [patch_size - size(patch, 1), patch_size - size(patch, 2)], 'post');
    end
    
    % Display or process the patch as needed
    % imshow(patch); pause(0.1); % Uncomment to display each patch
end