image processing - Is there a substitute for blockproc in Matlab?

Question

I've been using blockproc for processing images blockwise. Unfortunately, blockproc is part of the Image Processing Toolbox, which I don't have on my personal computer.

Is there a combination of functions in base Matlab that can substitute for blockproc?

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My initial guess was to use im2col to transform each block into columns, and then arrayfun to process each column. Then I realized that im2col is also a part of the Image Processing Toolbox, so that doesn't solve my problem.

Answer 1

Here is an example using MAT2CELL. It dividing the image into N-by-M tiles, and handles the case when the image size is not evenly divisible by the number of tiles.

%# 2D grayscale image
I = imread('coins.png');

%# desird number of horizontal/vertical tiles to divide the image into
numBlkH = 4;
numBlkW = 4;

%# compute size of each tile in pixels
[imgH,imgW,~] = size(I);
szBlkH = [repmat(fix(imgH/numBlkH),1,numBlkH-1) imgH-fix(imgH/numBlkH)*(numBlkH-1)];
szBlkW = [repmat(fix(imgW/numBlkW),1,numBlkW-1) imgW-fix(imgW/numBlkW)*(numBlkW-1)];

%# divide into tiles, and linearize using a row-major order
C = mat2cell(I, szBlkH, szBlkW)';
C = C(:);

%# display tiles i subplots
figure, imshow(I)
figure
for i=1:numBlkH*numBlkW
    subplot(numBlkH,numBlkW,i), imshow( C{i} )
end

The input image and the resulting tiles: