K-means & Image Segmentation - Computerphile

K-means sorts data based on averages. Dr Mike Pound explains how it works. Fire Pong in Detail: https://youtu.be/ZoZMMg1r_Oc Deep Dream: https://youtu.be/BsSmBPmPeYQ FPS & Digital Video: https://youtu.be/yniSnYtkrwQ Dr. Mike's Code: % This script is the one mentioned during the Computerphile Image % Segmentation video. I chose matlab because it's a popular tool for % quickly prototyping things. Matlab licenses are pricey, if you don't have % one (or, like me, work for an organisation that does) try Octave as a % good free alternative. This code should work in Octave too. % Load in an input image im = imread('C:\Path\Of\Input\Image.jpg'); % In matlab, K-means operates on a 2D array, where each sample is one row, % and the features are the columns. We can use the reshape function to turn % the image into this format, where each pixel is one row, and R,G and B % are the columns. We are turning a W,H,3 image into W*H,3 % We also cast to a double array, because K-means requires it in matlab imflat = double(reshape(im, size(im,1) * size(im,2), 3)); % I specify that initialisation shuold sample points at % random, rather than anything complex like kmeans++ initialisation. % Kmeans++ takes a long time if you are using 256 classes. % Perform k-means. This function returns the class IDs assigned to each % pixel, and in this case we also want the mean values for each class - % what colour is each class. This can take a long time if the value for K % is large, I've used the sampling start strategy to speed things up. % While KMeans is running, it will show you the iteration count, and the % number of pixels that have changed class since last iteration. This % number should get lower and lower, as the means settle on appropriate % values. For large K, it's unlikely that we will ever reach zero movement % (convergence) within 150 iterations. K = 3 [kIDs, kC] = kmeans(imflat, K, 'Display', 'iter', 'MaxIter', 150, 'Start', 'sample'); % Matlab can output paletted images, that is, grayscale images where the % colours are stored in a separate array. This array is kC, and kIDs are % the grayscale indices. colormap = kC / 256; % Scale 0-1, since this is what matlab wants % Reshape kIDs back into the original image shape imout = reshape(uint8(kIDs), size(im,1), size(im,2)); % Save file out, you need to subtract 1 from the image classes, since once % stored in the file the values should go from 0-255, not 1-256 like matlab % would do. imwrite(imout - 1, colormap, 'C:\Path\Of\Output\Image.png'); http://www.facebook.com/computerphile https://twitter.com/computer_phile This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: http://bit.ly/nottscomputer Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com