USING MATLAB

Consider the optical illusion below

The gray lines appear to bend and curve, but do they really? Write a script or a function to load in the image and turn all of the black squares to white squares, but keeping the gray lines as they are. The black squares are close to 0 (although not exactly 0 because of jpg artifacts), while the white squares are close to 255 (although not exactly 255 because of jpg artifacts).