MATLAB: Change Pixel intensity value

image analysisimage processing

Hi all,

I have an image(gray scale) whose pixel intensity values ranges from -0.5373 to 0.4744. I would like to change the intensity value which is lesser than 0 to 0. Can any one help me to solve this.

Thanks.

Best Answer

Say your image is x,

x(x<0) = 0;

Related Solutions

MATLAB: Changing values of pixels in an image pixel by pixel ( Thresholding )

First of all, it is not necessary to loop over all pixels individually. You can simply use operations on your image matrix, which would look like this:

% read in tiff image and convert it to double format

my_image = im2double(imread('picture.tif'));
my_image = my_image(:,:,1);
% perform thresholding by logical indexing
image_thresholded = my_image;
image_thresholded(my_image>3) = 256;
image_thresholded(my_image<0.5) = 0;
% display result

figure()
subplot(1,2,1)
imshow(my_image,[])
title('original image')
subplot(1,2,2)
imshow(image_thresholded,[])
title('thresholded image')

The line image_thresholded(my_image>3) = 256; is an example of logical indexing, it will assign the value 256 to all matrix elements in image_thresholded for which the same matrix element in my_image is larger than 3.

If you prefer looping over all pixels (which is not advisable due to its slow speed), your code should look something like this:

% read in tiff image and convert it to double format
my_image = im2double(imread('picture.tif'));
my_image = my_image(:,:,1);
% allocate space for thresholded image
image_thresholded = zeros(size(my_image));
% loop over all rows and columns
for ii=1:size(my_image,1)
    for jj=1:size(my_image,2)
        % get pixel value
        pixel=my_image(ii,jj);
          % check pixel value and assign new value
          if pixel<0.5
              new_pixel=0;
          elseif pixel>3
              new_pixel=256;
          else
              new_pixel = pixel;
          end
          % save new pixel value in thresholded image
          image_thresholded(ii,jj)=new_pixel;
      end
  end
% display result
figure()
subplot(1,2,1)
imshow(my_image,[])
title('original image')
subplot(1,2,2)
imshow(image_thresholded,[])
title('thresholded image')

Does this help you out?

MATLAB: How to change the more than one pixel values in gray scale image

Copying my answer from your duplicate question at http://www.mathworks.com/matlabcentral/answers/51939-how-i-can-change-the-certain-pixel-values-in-gray-scale-image:

Well, you shouldn't have accepted that answer so quickly if it didn't do what you asked. Here's how to "change the values of certain pixel to 1 that are closer to 1 and want to change values to 0 that are near to 0:

yourImage = yourImage >= 0.5;

Best Answer

Related Solutions

MATLAB: Changing values of pixels in an image pixel by pixel ( Thresholding )

MATLAB: How to change the more than one pixel values in gray scale image

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