subtract each pixel from average pixel value
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Harshit Kaushik
il 17 Mag 2019
Commentato: Image Analyst
il 11 Nov 2019
i have taken mean pixel value of an image and now i have to subtract from each pixel value of the image the average pixel value...how can i do it?
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Matt J
il 17 Mag 2019
It seems deceptively simple...
Image-meanValue
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Sara AR
il 11 Nov 2019
how can i remove the mean value of the 7x7 pixels around a picture? and lets say the picture is 512*512?
Image Analyst
il 11 Nov 2019
Use conv2().
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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Image Analyst
il 17 Mag 2019
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.
2 Commenti
Image Analyst
il 12 Ott 2019
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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