Is there a way to threshold the background out of the image, to leave only the object?

Hi folks,

I have images that look like the following, and I'm trying to threshold out the background. For some images, this is a very straightforward endeavour. For others, however, it's not that easy because the background and object have similar greyscale levels.

Ultimately, I want to use regionprops() to measure the object's properties.

May I please ask if there's a way to get around this?

My images look like this:

[kanika bhalla]

Have you tried thresholding method like graythreshold

Answer 1

[Image Analyst]

Try imbinarize(). Then check the mean gray level in the center of the mask image and compare it to the mean gray level at the top of the image. If the mask is dark in the center and bright around the top, then invert the mask. Something like (untested)

mask = imbinarize(grayImage);
[rows, columns] = size(mask);
row = round([rows/2-50 : rows/2+50]);
col = round([columns/2-50 : columns/2+50]);
if mean2(mask(1:10)) > mean2(mask(row, col))
    % Mask at top is white and in middle is black.  Need to invert it.
    mask = ~mask;
end

[Tanjena Azim]

@Image AnalystSir, sorry to barge in here....I am looking for your help and unable to make an individual qs... :(

sir, I am working on NROI based watermarking. I have used Watershed segmentation in an x-ray image of brain. But, now I am failing to separate the NROI from the ROI for further watermarking. Any simple code like foregroundValues, backgroundvalues,toolbox or anything alike would be helpful for me..., If u could provide me an example reagrding this,.... please please help me.....I am stuck there and can't proceed further :(

[Image Analyst]

I don't know what those are. Try

USC Annotated Computer Vision Bibliography

[Tanjena Azim]

@Image Analyst Sir can u plz simply suggest me a way to separate the NROI from ROI for watermark the NROI further??? i have already use watershed for segmentation....please

[Image Analyst]

@Tanjena Azim Like I already said, I don't know what NROI is. Plus I'm not a watermark expert. I've only played around with it a little bit - probably less than you.

And I don't think the original poster, @Teshan Rezel, knows or cares about watermarks. It's totally unrelated to this discussion thread.

[Tanjena Azim]

@Image Analyst Thank you, sir