MATLAB: How to define two tones in a grayscale image

grayscaleimage processingthresholdingultrasound

I have an ultrasound image with lots of gray tones. I want to threshold the image by defining two of its tones. The higher intensity (white tone) and the lowest intensity (darkest gray tone). All other tones in the middle should be eliminated.

How can I do this?

Thanks

Best Answer

You cannot eliminate colors in a gray-scale image, but only set them to another value.

img(img > 67 & img < 128) = 0;

Here all gray scale values between 68 and 127 are set to 0.

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MATLAB: How To remove black color from gray-scale image

It depends on the format of the image. For a UINT8 array:

Img = randi([0,255], 100, 100, 'uint8');  % Test data
Img(Img == 0) = 127;

Now black is replaced by a medium grey. The procedure for double format is equivalent, but a medium grey is 0.5.

MATLAB: Enhance grayscale image using normalization factor

Try this

img = rgb2gray(im2double(imread('pears.png')));
img(img<0) = 0;
mask = (0.15<=img)&(img<=0.4);
img(mask) = interp1([0.15 0.4], [0 0.4], img(mask));

Best Answer

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MATLAB: How To remove black color from gray-scale image

MATLAB: Enhance grayscale image using normalization factor

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