find the average pixel value of matrix of images

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michael bowen 2021-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/1613125-find-the-average-pixel-value-of-matrix-of-images

评论： Konrad 2021-12-17

hi i was wondering how to put a group of 10 images that are 1920 x 1080 into a matrix that is size 1920x1080x10. Im doing this to keep track of values for each pixel.

i have tried

for i = 1:10
    outputFileName = sprintf('bwImage%d.jpg', i);
    allImages{i} = imread(outputFileName);
end
B = mean(allImages);

but this creates and matrix size 1 x 10.

This matrix will be used to calculate the average value at each pixel location

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Answer 1

Konrad 2021-12-17

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编辑：Konrad 2021-12-17

在 MATLAB Online 中打开

Hi Michael,

allImages{i} = ... creates a cell-array containing the images.

If your images are all grayscale and of the same size you can use a 3-d array:

for i = 1:10
    outputFileName = sprintf('bwImage%d.jpg', i);
    allImages(:,:,i) = imread(outputFileName); % concatenate images in 3rd dimension
end
B = mean(allImages,3); % average across 3rd dimension

Best, K.

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Image Analyst 2021-12-17

在 MATLAB Online 中打开

You left out the allocation and some other robustness

numImages = 10;
allImages = zeros(1080, 1920, numImages, 'uint8'); % HDTV resolution -- 1080 lines (rows)
counter = 1;
for k = 1 : numImages
    outputFileName = sprintf('bwImage%d.jpg', k);
    fprintf('Reading in %s.\n', outputFileName);
    if isfile(outputFileName)
        allImages(:, :, counter) = imread(outputFileName); % concatenate images in 3rd dimension
        counter = counter + 1;
    else
        message = sprintf('File not found : ', outputFileName)
        uiwait(warndlg(message));
    end
end
% Crop if some images were missing.
if counter < numImages + 1
    allImages = allImages(:, :, 1:counter);
end
% Compute mean over all images of those images that we were able to read in.
meanImage = mean(allImages, 3); % average across 3rd dimension
% Display the image.
imshow(meanImage, []);