Patent ID: 7580074
Filing Date: 2009-08-25
Classification: H04N

Abstract:
1. A digital halftoning method for rendering a continuous-tone image effect on a printing or display device that can only represent a limited number of output tones, comprising the steps of: inputting an image to be rendered on a printing or display device as a continuous-tone image; performing a wavelet analysis for one row of pixels of the input image; and performing a halftoning algorithm to generate a corresponding output row to transform, wherein the halftoning algorithm contains a top-down dot assignment phase in which dots are assigned a new luminance value based on the wavelet analysis, and wherein the dot assignment phase comprises, for a one-dimensional spatial signal of length N a. performing a wavelet transform on the input row to get wavelet coefficients; b. obtaining a total number of dots needed for the row based on a reconstruction value cA c. quantizing the average density to a nearest integer; d. dividing the row into two sub-intervals; e. taking a reconstruction value of a detail coefficient cD f. iteratively repeating steps a. through e. until the finest level that contains a single pixel is reached.