subtract each pixel from average pixel value

kernel = ones(7, 7);
kernel(4, 4) = 0; % Don't include central pixel when computing mean.
kernel = kernel / sum(kernel(:)); % Normalize.  Mean is the sum of the 48 pixels divided by 48
blurredImage = conv2(double(grayImage), kernel, 'same'); % Get mean in a 7x7 window around every pixel.
output = double(grayImage) - blurredImage; % Subtract local mean.

You can do it without creating a temporary image if you construct the kernel differently:

kernel = -ones(7, 7); % Minus 1 means subtract the values.
kernel(4, 4) = 0; % Don't include central pixel when computing mean.
kernel = kernel / sum(kernel(:)); % Normalize.  Mean is the sum of the 48 pixels divided by 48
kernel(4,4) = 1;
output = conv2(double(grayImage), kernel, 'same');

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Answer 2

Image Analyst 2019-5-17

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/462742-subtract-each-pixel-from-average-pixel-value#answer_375555

在 MATLAB Online 中打开

Try (for an integer gray level image):

newImage = double(yourImage) - meanValue;

where you said you already have the meanValue, or

meanValue = mean2(yourImage);

if you don't.

newImage will be a floating point image, which is the only way to handle negative values in the subtraction.

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Ahmad Alenezi 2019-10-10

I think the last answer is right !

Image Analyst 2019-10-12

Correct. And since about half the values will be negative if you subtract the mean, the accepted answer will be wrong for about half the pixels, whereas my code won't be wrong for any of them.

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