Removing People from Vacation Snaps

2012-06-26 by Falko Schindler, tagged as matlab

Taking multiple images of the very same scene, captured using a tripod, we are going to remove moving objects by simply taking the median (i.e. the robust average) of all avaiable images.

Loading all images
Compute the median

Loading all images

We load all images into a large 4D matrix (height, width, channels, images). To speed up the process a little and to save memory, we scale down all images by some constant factor.

scale = 0.25;
images = dir('*.JPG');
info = imfinfo(images(1).name);
img = zeros(info.Height * scale, info.Width * scale, 3, numel(images), 'uint8');
for i = 1 : numel(images)
    img(:, :, :, i) = imresize(imread(images(i).name), scale);
end
collage = imresize([ ...
    img(:, :, :,  1), img(:, :, :,  2), img(:, :, :,  3);
    img(:, :, :,  4), img(:, :, :,  5), img(:, :, :,  6);
    img(:, :, :,  7), img(:, :, :,  8), img(:, :, :,  9);
    img(:, :, :, 10), img(:, :, :, 11), img(:, :, :, 12);
    img(:, :, :, 13), img(:, :, :, 14), img(:, :, :, 15);
    img(:, :, :, 16), img(:, :, :, 17), img(:, :, :, 18);
    img(:, :, :, 19), img(:, :, :, 20), img(:, :, :, 21);
    img(:, :, :, 22), img(:, :, :, 23), img(:, :, :, 24)], 1 / 5);
imshow(collage, 'Border', 'tight');
imwrite(collage, 'collage.png');

Compute the median

Taking the median over all images will preserve static objects like background, buildings and monuments, but suppress deviations caused by moving objects such as people, birds etc.

med = median(img, 4);
imshow(med, 'Border', 'tight');
imwrite(med, 'median.png');

Falko Schindler