Determination of the shape of a binary object by means of chosen initial phases and Sayre's equation

The binary object treated is a square. We first use a set of initial phases to determine the symmetry of the object. The result shows a well-shaped image, and preserves symmetry of the object. We then use another set of initial phases. The result has gross shape of a square with approximately correct dimensions. Sayre's equation is applied to refine the gross shape. After iterations, the result shows an image which is close to a square with sharp boundary and has approximately correct dimensions. The charge densities of the image are approximately evenly distributed, scattering about the value of 1, and has no negative charge density. The shape of the binary object is obtained. The initial phases or the gross shape can be used as starting phases or starting envelope in other iterative algorithms.