Crop out unwanted part from an image.

Dear friends, I want to crop out extra part of CT Head image. I mean i want my image should have only required part of the image by removing unwanted black background.

[Sven]

So you have a single 2D image?

Let's say you want to remove the top and bottom 5 rows and the first 10 columns:

originalIm = rand(512,512);

croppedIm = originalIm(6:end-5, 11:end);

If this *doesn't* answer your question, please realise that you need to make your question more specific.

Answer 1

[Walter Roberson]

Threshold the image so that the "black" background values are assigned 0. Suppose we refer to that result as ImThr . Then

foregroundcol = any(ImThr);
firstforegroundcol = find(foregroundcol, 1);
lastforegroundcol = find(foregroundcol, 1, 'last');

foregroundrow = any(ImThr,2);
firstforegroundrow = find(foregroundrow, 1);
lastforegroundrow = find(foregroundrow, 1, 'last');

And then we can extract the foreground from the frame:

foregroundImg = OriginalImg(firstforegroundrow:lastforegroundrow, firstforegroundcol:lastforegroundcol);

Note that this construction assumes there is no outline or annotations around the image, just image.

Answer 2

[Image Analyst]

See my BlobsDemo: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862

It does exactly this with the standard coins image, assuming you can determine foreground and background solely by intensity thresholding.