Patent ID: 7716627

Claim:
A computer-implemented method comprising: (a) using an electronic processor, computing a first cost function for a first nonpixelated mask to obtain a first value; (b) altering the first nonpixelated mask in a frequency domain to obtain a second nonpixelated mask; (c) using the electronic processor, computing the first cost function for the second nonpixelated mask to obtain a second value; (d) repeating (b) and (c) until the second value is less than the first value; (e) generating a second cost function by applying a quantization function to the second nonpixelated mask, wherein the quantization function regularizes a mask value of the second nonpixelated mask to one of at least two bias quantization values; (f) using the electronic processor, computing the second cost function for the second nonpixelated mask to obtain a third value; (g) altering the second nonpixelated mask in the frequency domain to obtain a third nonpixelated mask; (h) using the electronic processor, computing the second cost function for the second and third nonpixelated masks to obtain a fourth value; (i) repeating (g) and (h) until the fourth value is less than the third value; and (j) outputting the third nonpixelated mask as a final regularized mask.