how to do logarithmic image normalization?
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mahesh chathuranga
le 13 Oct 2013
Commenté : Adam Nustian
le 19 Juin 2016
what is logarithmic image normalization?how to do it?(range is 0-255)
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Image Analyst
le 13 Oct 2013
Modifié(e) : Image Analyst
le 15 Oct 2013
I suppose you just get a new image where the image is the log of the pixel value. It's used to enhance dark areas by expanding their range, while not clipping bright areas. Run the code below for a demo.
workspace; % Make sure the workspace panel is showing.
% Read in and display the original gray scale image.
grayImage = imread('Cameraman.tif');
grayImage = double(grayImage);
subplot(2,1,1);
imshow(grayImage, []);
axis on;
title('Original Image', 'FontSize', 15);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
% Take the log of it. Add 1 to avoid taking log of zero.
logImage = log(grayImage+1);
% Normalize to the range 0-1.
normalizedImage = mat2gray(logImage);
% Display it.
subplot(2,1,2);
imshow(normalizedImage, []);
axis on;
title('Log Image', 'FontSize', 15);
% If you want a uint8 version, then you can multiply by 255
% uint8Image = uint8(255 * normalizedImage);
msgbox('Note how the coat has more details');
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Adam Nustian
le 19 Juin 2016
ImageAnalyst Are you available to review a paper on Log. Image Processing for an international conference?
Thanks
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Anand
le 14 Oct 2013
It sounds like you want to just take the log of the image and rescale the range from 0 to 255. This is something you might want to do to visualize a frequency domain signal. Here's how you can do that:
% take logarithm of image.
imLog = log(im);
% normalize
minLog = min(imLog(:));
maxLog = max(imLog(:));
imLogNorm = 255 * (imLog - minLog)./(maxLog-minLog);
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