Using Linear indicies to create new image

So i have an image that I have used region props to find the pixels that are contained in certain objects.

With this function I have the linear indecies for each pixel. I want to use these indicies to create a new binary image that is the same size as the original with true (Intensity=1) pixels for each of the linear index that correlated to the computed object.

Hopefully this makes sense. I am sure there is a simple solution that would solve this but as of right now I can't figure out what that is.

[Mathieu NOE]

it would certainly be more efficient if you could share your code

Answer 1

[Image Analyst]

You need to label your binary image and then use ismember to extract out just certain ID(s) to a new binary image. For example

labeledImage = bwlabel(mask);
% Extract out blobs #3 and 8 to a new binary image:
mask2 = ismember(labeledImage, [3, 8]);

See my Image Segmentation Tutorial in my File Exchange for a full demo.

Image Analyst's File Exchange

It's a generic, general purpose demo of how to threshold an image to find blobs, and then measure things about the blobs, and extract certain blobs based on their areas or diameters.

[DGM]

Or to just get all the masks at once

% a mask with 5 blobs
inpict = imread('blobs.png');
mask = im2gray(inpict)>64;
imshow(mask,'border','tight')

% create label image
[labeledImage nblobs] = bwlabel(mask);

% a complete set of masks as a 4D stack
maskstack = labeledImage == reshape(1:nblobs,1,1,1,[]);

% show the mask stack using montage
montage(maskstack,'bordersize',3,'backgroundcolor',[0.2 1 0.8])

Answer 2

[Matt J]

stats=regionprops(BW,'PixelIdxList');

Z0=false(size(BW));

for i=1:numel(stats)
    
    Z=Z0;
    Z(stats(i).PixelIdxList)=1;
    
    stats(i).BW=Z;  %isolated BW images of each region
    
end