I'm going to generalize a little bit. Scaling factor can be set as an internal parameter. The code supports any number of image channels. This can be turned into a function as needed.
inpict = imread('peppers.png');
% the main parameter
rsfactor = 4; % i'm using 4 so the change is noticeable on the forum
% the last output of size() is a product term, not strictly a size
[rows, cols, chans, ~] = size(inpict);
% make sure the size is compatible with the scaling factor
if any(mod([rows cols],rsfactor))
error('HALVEIMAGE: page geometry must be an integer multiple of %d',rsfactor)
end
% preallocate output image to the same class as the input
outpict = zeros(rows/rsfactor,cols/rsfactor,chans,class(inpict));
% increment in steps of rsfactor
for i = rsfactor:rsfactor:rows
for j = rsfactor:rsfactor:cols
% get sample region
r_idx = (i-rsfactor+1):i;
c_idx = (j-rsfactor+1):j;
smallA = inpict(r_idx, c_idx, :); % all channels
% average on first two dimensions only
outpict(i/rsfactor, j/rsfactor, :) = mean(smallA,1:2);
end
end
size(inpict)
size(outpict)
imshow(outpict)
