image() display image and adjust contrast automatically

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Sun 2012-4-15

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Hi, I have a 16-bit gray image which has a intensity value between [0 5000].I want to use image to display the image matrix and automatically display the image. However, I don't find and image handle properties about this.I know imshow() can do this easily, but I have to use image() now.

Thanks, Sun Tao

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Answer 1

Image Analyst 2012-4-15

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I played around a bit with image with 16 bit images and various colormaps and couldn't get it to work (to display the complete range properly). The only way I could do it was to convert it to an 8 bit image.

% Create sample 16 bit image.
rows = 600;
columns = 800;
ramp = linspace(1, 5000, columns);
grayImage = uint16(repmat(ramp, [rows, 1]));
% imshow(grayImage, []);  % This works.
% image(grayImage);  % This doesn't seem to work no matter what colormap I used.
% Convert to normalized uint8 image.
g=uint8(255*mat2gray(grayImage));
image(g); % Now it works.
% Apply gray scale color map.
colormap(gray(256));
colorbar;

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Sun 2012-4-16

Hi,

Thanks for the reply! This works and now it can display. Althouth I may still use 16-bit because this will not lose information. But at this moment it's good enough.

Sun Tao

Image Analyst 2012-4-16

Go ahead and use 16 bits everywhere you do math on it. I just converted to 8 bit for display only so no information is lost because you have only an 8 bit display (24 bit RGB) - you don't have a 16 bit per channel color display so even if you passed a 16 bit image to some display routine, it would have to convert to 8 bits internally *anyway* when it displayed it since the display can't handle 16 bits. Make sense?

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