matlab:将图像分成重叠的块 [英] matlab: splitting images into overlapping blocks

问题描述

我有一个尺寸为[M,N]的图像，我想将其拆分为尺寸为[rr,cc]的overlapping个块.每个块移位yy和xx像素.下面的代码完成了这项工作.有没有更有效的方法来做到这一点?例如避免for循环?我找到的解决方案方法#1 或

I've an image of size [M,N], which I would like to split into overlapping blocks of size [rr,cc]. Each block is shifted by yy and xx pixels. The code below does the job. Is there any more efficient way to do that? e.g. avoiding the for loops? The solutions that I found approach #1 or approach #2 where mainly for non-overlapping blocks.

SOL 1

Im = imread('cameraman.tif');
[M,N,~] = size(Im);
rr = 64; cc = 64; xx = 32; yy = 32;

numBlocksYY = numel(1:rr-xx:(M-(rr-1)));
numBlocksXX = numel(1:cc-yy:(N-(cc-1)));
[numBlocksYY, numBlocksXX]
C = cell(numBlocksYY*numBlocksXX,1);
counter = 1;
for ii=1:rr-xx:(M-(rr-1))
    for jj=1:cc-yy:(N-(cc-1))
        fprintf('[%d:%d, %d:%d]\n',ii,ii+rr-1,jj,jj+cc-1);
        C{counter} =  Im(ii:(ii+rr-1), jj:(jj+cc-1), : );
        counter = counter + 1;
    end
    fprintf('\n');
end

figure;
for ii=1:numBlocksYY*numBlocksXX
    subplot(numBlocksYY,numBlocksYY,ii), imagesc( C{ii} ); axis image; colormap gray;
end

SOL 2 受到此帖子中提出的一些解决方案的启发，我尝试使用ndgrid提出解决方案，但是以后如何填充cell C输出并使用XX和YY索引访问子图像?我也很好奇，看看是否还有其他解决方案:-)?

SOL 2 Inspired by some of the solutions proposed in this post, I tried to come to a solution using ndgrid, but how could I later on fill the output cell C and access to the sub-images using the XX and YY indexes? I'm also curious to see if there are any other solutions :-) ?

[YY,XX]=ndgrid( 1:(rr-xx):(M-(rr-1)) , 1:(cc-yy):(N-(cc-1)));

推荐答案

您可以从 SOL 2 中给出的XX和YY获取输出cell C，如下所示:

You can obtain the output cell C from XX and YY given in SOL 2 as follows:

% indices of the first rr x cc block
IDX1 = bsxfun(@plus, (1:rr)', ((1:cc)-1)*M);
% offset in indices for each block
offset = (XX(:)-1) + (YY(:)-1)*M;
% indices of each block, the block is indexed with the 3rd dimension
IDX = bsxfun(@plus, IDX1, reshape(offset, [1 1 numel(offset)]));
% convert to cell of blocks
C = mat2cell(Im(IDX), rr, cc, ones(1, numel(XX)));

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