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how to display a matrix with negative values as a image

Asked by mahesh chathuranga on 30 Sep 2013
Latest activity Answered by Image Analyst on 30 Sep 2013

some arithmatic operations gives negative values.is it a problem for displaying the image.how to display a matrix with negative values as a image

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mahesh chathuranga

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3 Answers

Answer by Simon on 30 Sep 2013

There are many ways of doing this

  1. take the absolute value with "abs"
  2. shift all values so that you don't have negatives anymore
  3. scale the values so that you have 0 in the middle of the RGB values
  4. ...

(may grayscale image is most suitable for this?)

1 Comment

mahesh chathuranga on 30 Sep 2013

please telll me how can i do 2. and 3.

Simon
Answer by Jan Simon on 30 Sep 2013
Edited by Jan Simon on 30 Sep 2013

It depends on what you want to display. Some examples:

data = 1 + 2 .* randn(200, 200);  % Test data

1. Set all negative value to zero, scale the positive values to be in the range of [0,1]:

img1 = max(data, 0);
img1 = img1 / max(img1(:));

2. Shift all values to the positive range, that scale again as above:

img2 = data - min(data(:));
img2 = img2 / max(img2(:));

3. There is an infinite number of possibilities for pseudo-color images. You could e.g. define colors for different intervals by dividing the total range max(data(:)) - min(data(:)) into 17 different intervals and using the 2nd output of histc to get the interval for each pixel.

4. Perhaps you are talking about RGB images? Then even more possible mappings exist.

Conclusion: Please post any details about the wanted procedure. We cannot guess them.

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Jan Simon
Answer by Image Analyst on 30 Sep 2013

I gave you some answers in your duplicate question: http://www.mathworks.com/matlabcentral/answers/88637#comment_171537 Why do you have two questions on the same question? Doesn't that make it confusing for you , and us, when you have two places to go to look for answers?

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Image Analyst

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