mask2poly(mask)

P = MASK2POLY(BW) reverses the POLY2MASK function in Image Processing Toolbox. It takes a binary image BW and returns an array of struct, P. Each element of P defines either a polygon or a hole within a polygon.
This function requires another FEX function: contourcs (http://www.mathworks.com/matlabcentral/fileexchange/28447)
Example:
mask = imread('circuit.tif')>100;
P = mask2poly(mask);
figure;
imagesc(mask);
axis on; box off; grid on;
hold on;
for n = 1:numel(P)
if P(n).IsFilled
color = 'w';
else
color = 'y';
end
plot(P(n).X,P(n).Y,color);
end
hold off;