how to do logarithmic image normalization?

what is logarithmic image normalization?how to do it?(range is 0-255)

Answer 1

[Image Analyst]

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');

[Adam Nustian]

ImageAnalyst Are you available to review a paper on Log. Image Processing for an international conference?

Thanks

Answer 2

[Anand]

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);