This is a simple way. Select all low-chroma regions and fill with white.
A = imread('https://www.mathworks.com/matlabcentral/answers/uploaded_files/853710/pic1.jpg');
Ayiq = rgb2ntsc(A);
mask = hypot(Ayiq(:,:,2),Ayiq(:,:,3))<0.1;
mask = repmat(mask,[1 1 3]);
A(mask) = 255;
imshow(A)
The compression artifacts from the use of a JPG format make the color selection more difficult than it really should be. Clearing the entire background instead of just the dots helps by getting rid of all the artifact halos surrounding the objects.