aims to minimize the difference between
target halftone image and the synthesized QR code. We formulate
the minimization as optimizing a module-wise image difference between
the assigned pattern and corresponding halftone patch while
favoring the smoothness between neighboring patterns. We construct
a graph G = (V;E) where the nodes V correspond to the
modules in M. Two nodes mi and mj are connected by an edge
eij 2 E, if mj is in the 4-connected neighborhood of mi. The
regularization energy is defined as