You can use a mask of the circles, determined from A, on B and analyze what is remaining.
% Creates a mask from one image and applies it to an image.
clc; % Clear the command window.
workspace; % Make sure the workspace panel is showing.
clearvars;
close all;
format long g;
format compact;
fontSize = 20;
rgbImage = imread('coloredChips.png');
% Get the dimensions of the image. numberOfColorBands should be = 3.
[rows, columns, numberOfColorChannels] = size(rgbImage);
subplot(3, 2, 1);
imshow(rgbImage)
title('Original RGB Image', 'fontSize', fontSize);
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off')
% d = imdistline;
% delete(d);
grayImage = rgb2gray(rgbImage);
subplot(3, 2, 2);
imshow(grayImage);
drawnow;
title('Gray Scale Image', 'fontSize', fontSize);
% [centers, radii] = imfindcircles(rgbImage,[20 25],'ObjectPolarity','dark')
[centers, radii] = imfindcircles(rgbImage,[20 25],'ObjectPolarity','dark', ...
'Sensitivity',0.9)
subplot(3, 2, 3);
imshow(rgbImage);
h = viscircles(centers, radii);
title('Original RGB Image with Circles in Overlay', 'fontSize', fontSize);
% Make a binary image mask
subplot(3, 2, 4);
mask = false(rows, columns);
for k = 1 : length(centers)
% Create a logical image of a circle with specified
% diameter, center, and image size.
% First create the image.
[columnsInImage rowsInImage] = meshgrid(1:columns, 1:rows);
% Next create the circle in the image.
centerX = centers(k, 1);
centerY = centers(k, 2);
radius = radii(k);
circlePixels = (rowsInImage - centerY).^2 ...
+ (columnsInImage - centerX).^2 <= radius.^2;
% circlePixels is a 2D "logical" array.
% Now, display it.
imshow(circlePixels) ;
mask(circlePixels) = true;
imshow(mask);
drawnow;
end
imshow(mask);
title('Binary image mask', 'fontSize', fontSize);
% Mask the image using bsxfun() function
maskedRgbImage = bsxfun(@times, rgbImage, cast(mask, 'like', rgbImage));
subplot(3, 2, 5);
imshow(maskedRgbImage);
title('Masked RGB Image', 'fontSize', fontSize);
