Split image into blocks and rejoin....

Question

Saud Alfalasi 2020-12-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/695525-split-image-into-blocks-and-rejoin

评论： Saud Alfalasi 2020-12-19

采纳的回答： Image Analyst

在 MATLAB Online 中打开

Im trying to split an image into block

I will eventually do something to each block

I then want to rejoin blocks to make a new image.

When trying to rejoin my blocks I'm getting the below error:

Unable to perform assignment because the size of the left side is 50-by-1-by-50 and the size of the right side is 50-by-50-by-3.

Error in blocktest (line 57)

imMatr((r-1)*blockRows+1:r*blockRows,rem(rows, blockSizeR),...

Can someone please help

I = imread('hide.jpg');
[rows, columns, planes] = size(I);
 
blockSizeR = 50; % Rows in block.
blockSizeC = 50; % Columns in block.
FullBlockRows = floor(rows / blockSizeR);
blockVectorR = [blockSizeR * ones(1, FullBlockRows), rem(rows, blockSizeR)];
% Figure out the size of each block in columns.
FullBlockColums = floor(columns / blockSizeC);
blockVectorC = [blockSizeC * ones(1, FullBlockColums), rem(columns, blockSizeC)];
% Create the cell array
Cellarray = mat2cell(I, blockVectorR, blockVectorC, planes);
 
 
% Display all the blocks.
count =1;
plotIndex = 1;
numPlotsR = size(Cellarray, 1);
numPlotsC = size(Cellarray, 2);
for r = 1 : numPlotsR
    for c = 1 : numPlotsC
        
        fprintf('plotindex = %d,   c=%d, r=%d\n', plotIndex, c, r);
        subplot(numPlotsR, numPlotsC, plotIndex);
        rgbBlock = Cellarray{r,c};
        imshow(rgbBlock);% Could call imshow(ca{r,c})
        [rowsB, columnsB, numberOfColorBandsB] = size(rgbBlock);
        caption = sprintf('B#%d/%d', ...
            plotIndex, numPlotsR*numPlotsC);
        title(caption);
        drawnow;
        
        % set dimensions for cell holding RGB Blocks
        num_cols = FullBlockColums;
        num_rows = FullBlockRows;
        cellBlocks = cell(num_rows, num_cols);
        
        % input block dimensions
        blockRows = blockSizeR;
        blockCols = blockSizeC;
        
        % calculate dimensions of image
        numPixWidth = rows;
        numPixHeight = columns;
        numChannels = 3;
        
        % allocate memory with zeros matrix
        imMatr = zeros(numPixWidth, numPixHeight, numChannels);
        
        block = Cellarray{r,c}
        
        fprintf('plotindex = %d,   col=%d, row=%d\n', plotIndex, c, r);
        
        figure
        imshow(block)
        
        imMatr((r-1)*blockRows+1:r*blockRows,rem(rows, blockSizeR),...
            (c-1)*blockCols +1:c*blockCols,rem(columns, blockSizeC), :) = block;
        figure
        imshow(imMatr)
        
        
        % Increment the subplot to the next location.
        plotIndex = plotIndex + 1;
        
        
    end
    
    % show matrix
    figure;
    imshow(imMatr(:,:,1)); %showing only red channel
    
    
end

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Answer 1

Image Analyst 2020-12-16

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/695525-split-image-into-blocks-and-rejoin#answer_577305

在 MATLAB Online 中打开

Count the commas in

        imMatr((r-1)*blockRows+1:r*blockRows,rem(rows, blockSizeR),...
            (c-1)*blockCols +1:c*blockCols,rem(columns, blockSizeC), :) = block;

You have 4 of them, meaning 5 dimensions. You have

row1 = (r-1)*blockRows+1
row2 = r*blockRows,
columnRange = rem(rows, blockSizeR),...
index3RangeStart =  (c-1)*blockCols +1
index3RangeEnd = c*blockCols
index4 Range = rem(columns, blockSizeC)
index5 = :; % (everything);

Why do yo uhave 5 dimensions? What's with those rem() functions in there???

I suggest you simplify it by making 4 variables:

row1 = whatever
row2 = whatever
col1 = whatever
col2 = whatever

% Now use them

imMatr(row1:row1, col1:col2, :) = block;

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Saud Alfalasi 2020-12-19

在 MATLAB Online 中打开

Hey man, thanks for the swift reply,

You can use any colour image.

Come on buddy make my christmas wish come true: all i want is to have a new image of the combined blocks. In this case because I haven't actually done anything to any of the blocks it should just look exactly the same as the orignal image.

Saud

I = imread('hide.jpg');
[rows, columns, planes] = size(I);
 
blockSizeR = 50; % Rows in block.
blockSizeC = 50; % Columns in block.
FullBlockRows = floor(rows / blockSizeR);
blockVectorR = [blockSizeR * ones(1, FullBlockRows), rem(rows, blockSizeR)];
% Figure out the size of each block in columns.
FullBlockColums = floor(columns / blockSizeC);
blockVectorC = [blockSizeC * ones(1, FullBlockColums), rem(columns, blockSizeC)];
% Create the cell array
Cellarray = mat2cell(I, blockVectorR, blockVectorC, planes);
 
 
% Display all the blocks.
count =1;
plotIndex = 1;
numPlotsR = size(Cellarray, 1);
numPlotsC = size(Cellarray, 2);
for r = 1 : numPlotsR
    for c = 1 : numPlotsC
        
        fprintf('plotindex = %d,   c=%d, r=%d\n', plotIndex, c, r);
        subplot(numPlotsR, numPlotsC, plotIndex);
        rgbBlock = Cellarray{r,c};
        imshow(rgbBlock);% Could call imshow(ca{r,c})
        [rowsB, columnsB, numberOfColorBandsB] = size(rgbBlock);
        caption = sprintf('B#%d/%d', ...
            plotIndex, numPlotsR*numPlotsC);
        title(caption);
        drawnow;
        
        % set dimensions for cell holding RGB Blocks
        num_cols = FullBlockColums;
        num_rows = FullBlockRows;
        cellBlocks = cell(num_rows, num_cols);
        
        % input block dimensions
        blockRows = blockSizeR;
        blockCols = blockSizeC;
        
        % calculate dimensions of image
        numPixWidth = rows;
        numPixHeight = columns;
        numChannels = 3;
        
        % allocate memory with zeros matrix
        imMatr = zeros(numPixWidth, numPixHeight, numChannels);
        
        block = Cellarray{r,c}
        
        fprintf('plotindex = %d,   col=%d, row=%d\n', plotIndex, c, r);
        row1 = (r-1)*blockRows+1
        row2 = r*blockRows
        col1 = (c-1)*blockCols +1
        col2 = c*blockCols
        imMatr(row1:row2, col1:col2, :) = block;
        % Increment the subplot to the next location.
        plotIndex = plotIndex + 1;
        
        
    end
    
    % show matrix
    figure;
    imshow(imMatr(:,:,1)); %showing only red channel
end

Image Analyst 2020-12-19

在 MATLAB Online 中打开

You forgot to check to see if any of the blocks would be past the edge of the image when you pasted them on to the output image. Corrected code is below:

I = imread('peppers.png');
[rows, columns, planes] = size(I);
blockSizeR = 50; % Rows in block.
blockSizeC = 50; % Columns in block.
FullBlockRows = floor(rows / blockSizeR);
blockVectorR = [blockSizeR * ones(1, FullBlockRows), rem(rows, blockSizeR)];
% Figure out the size of each block in columns.
FullBlockColums = floor(columns / blockSizeC);
blockVectorC = [blockSizeC * ones(1, FullBlockColums), rem(columns, blockSizeC)];
% Create the cell array
Cellarray = mat2cell(I, blockVectorR, blockVectorC, planes);
% Display all the blocks.
count = 1;
plotIndex = 1;
numPlotsR = size(Cellarray, 1);
numPlotsC = size(Cellarray, 2);
% Create an output image
outputImageRows = sum(blockVectorR)
outputImageColumns = sum(blockVectorC)
reconstructedRgbImage = zeros(outputImageRows, outputImageColumns, planes, 'uint8');
for r = 1 : numPlotsR
	for c = 1 : numPlotsC
		fprintf('Plot index = %d,   c=%d, r=%d\n', plotIndex, c, r);
		subplot(numPlotsR, numPlotsC, plotIndex);
		
		% Get this block.
		rgbBlock = Cellarray{r, c};
		
		% Display this block.
		imshow(rgbBlock);% Could call imshow(ca{r,c})
		[rowsB, columnsB, numberOfColorBandsB] = size(rgbBlock);
		caption = sprintf('B#%d/%d', ...
			plotIndex, numPlotsR*numPlotsC);
		title(caption);
		drawnow;
		
		% Load this block into the output matrix.
		fprintf('plotindex = %d,   col=%d, row=%d\n', plotIndex, c, r);
		
		row1 = (r-1)*blockRows+1;
		row2 = r*blockRows;
		if row2 > outputImageRows
			row2 = outputImageRows;
		end
		col1 = (c-1)*blockCols +1;
		col2 = c*blockCols;
		if col2 > outputImageColumns
			col2 = outputImageColumns;
		end
		fprintf('Pasting block #%d into rows %d-%d, columns %d-%d\n', ...
			plotIndex, row1, row2, col1, col2);
		
		reconstructedRgbImage(row1:row2, col1:col2, :) = rgbBlock;
		
		% Increment the subplot to the next location.
		plotIndex = plotIndex + 1;
		
	end
	
end
% Show images
figure;
subplot(2, 2, 1);
imshow(reconstructedRgbImage); % Showing full RGB iamge.
title('Reconstructed RBG Image', 'FontSize', 20);
subplot(2, 2, 2);
imshow(reconstructedRgbImage(:,:,1)); %showing only red channel
title('Red Channel Image', 'FontSize', 20);
subplot(2, 2, 3);
imshow(reconstructedRgbImage(:,:,2)); %showing only green channel
title('Green Channel Image', 'FontSize', 20);
subplot(2, 2, 4);
imshow(reconstructedRgbImage(:,:,3)); %showing only blue channel
title('Blue Channel Image', 'FontSize', 20);

Saud Alfalasi 2020-12-19

Change your name to Image Angel. Wow oh wow.

Saud Alfalasi 2020-12-19

Thank you so so much, I hope you're able to get this message. I wish to find a way to express my gratitude.

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Split image into blocks and rejoin....

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