How to do a binarization of this image?

Dear all,

Please, can anybody tell me, how to do a binarization of this image?

Step by step please, I´m new in this section.

Thank you for your answers.

Answer 1

[Image Analyst]

You can threshold, like

grayImage = rgb2gray(yourRGBImage);
binaryImage = grayImage > someThresholdValue;
imshow(binaryImage);

Or see my interactive thresholding app: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

[Veronika]

Still I have this error:

Error using rgb2gray>parse_inputs (line 81)
MAP must be a m x 3 array.

Error in rgb2gray (line 35)
X = parse_inputs(varargin{:});

Error in binarizaceopetazase (line 3)
grayImage = rgb2gray('thorax-mdl.jpg');

[Image Analyst]

You need to pass it a numerical array, not a character array (the filename string). imshow() can work like that but not rgb2gray. Try

grayImage = imread('thorax-mdl.jpg');
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorChannels] = size(grayImage);
if numberOfColorChannels > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end

[Veronika]

Finally, it´s working.

Thank you.

Answer 2

[George]

Take a look at this example and im2bw.

[Veronika]

Thanky you for link.

I tried this, but this part of code doesn´t work.

I3 = imadjust(I2);
imshow(I3);

It always appears this type of error.

Error using imadjust>parseInputs (line 207)
Specified syntax IMADJUST(I) is only supported for 2-D grayscale images. Additional input arguments are required for use
with RGB images.

Error in imadjust (line 97)
    parseInputs(varargin{:});

Error in binarizace_image_dalsi_pokus (line 14)
I3 = imadjust(I2);

What is wrong? Thank you for your answer.

[George]

It's saying that your image isn't grayscale. Take a look at this example.

[Image Analyst]

Then why did you accept the answer if it's not working?