Hi, I need some help writing matlab code for the conversion of a greyscale image

Question

Hi, I need some help writing matlab code for the conversion of a greyscale image to 8-bit per pixel greyscale, using block truncation coding. Can someone please provide some code for me to use and explain how the code works?

Explanation / Answer

%Block Truncation Coding, or BTC, is a type of lossy image compression %technique for greyscale images %% Prepare Workspace tic clear;close all; %% Input Image I=imread('elaine.png'); if size(I,3)==3 I=rgb2gray(I); end %size of image [M,N]=size(I); %convert to double I=double(I); Y=zeros(M,N); %% compression blksize=2; %Block Size mu=colfilt(I,[blksize,blksize],'distinct',@(x) ones(blksize^2,1)*mean(x)); sigma=colfilt(I,[blksize,blksize],'distinct',@(x) ones(blksize^2,1)*std(x)); q=I>mu; q=colfilt(q,[blksize,blksize],'distinct',@(x) ones(blksize^2,1)*sum(x)); m=blksize^2; %length*width of block a=mu-sigma.*(sqrt(q./m-q)); %low mean b=mu+sigma.*(sqrt(m-q./q)); %high mean H=I>=mu; %elements of Bitmap Y(H)=a(H); Y(~H)=b(~H); Y=uint8(Y); %output BTC image figure,imshow(Y) toc

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