| 摘要 |
<p>A two-dimensional array of binary values is used to control operation of a bi-level imaging device. The array of binary values is formed by applying an enhanced array g(u,v) to a two-dimensional array of threshold values. A two-dimensional array of pixel values f(u,v) is used to form the enhanced array g(u,v) such that g(u,v) = mf + k[f(u,v) - mf] where mf is the average value of f(u+a, v+b) from a = -L to a = +L and b = -M to b = +M and k is a gain function which depends on the standard deviation in f(u+c, v+d) from c = -N to c = +N and d = -P to d = +P. L, M, N and P define the sub-array over which the standard deviation is calculated. Preferably, L, M, N and P are each equal to 2. The value of k is a decreasing function of the standard deviation: the larger the standard deviation, the smaller the gain factor k. The rate at which k decreases with increase in the standard deviation depends on the edge sampling characteristics of the array of threshold values.</p> |
