Improving the perceived quality of half tone secret images in visual cryptography

In this work, a method that aims to improve the half tone images hidden by visual cryptography is proposed. Visual cryptography produces shared images each of which does not have any hint about the hidden image. When these shared images stacked over one another, the hidden image is revealed without any need of post processing or decoding. The operations that make it impossible to guess the hidden image from a single shared one, also causes the deterioration of the hidden image to a degree. In this work, it is aimed to process the hidden image in a way to reduce the disruption caused by the operations required by visual cryptography. A new method for producing half tone images from gray tone images that is suitable for our aim is introduced and it is shown that how this method produces images that have higher perceptual quality after visual cryptography is applied.