Halftoning by enhanced error diffusion
First Claim
1. A method for halftoning image data for each of plural pixels, comprising the steps of:
- selecting one of plural threshold masks based on intensity of the image data for a target pixel plus an accumulated error;
determining a halftone output value for the target pixel based on a comparison between a threshold in the selected threshold mask and the image data plus accumulated error for the target pixel; and
diffusing error between the halftone output value and the image data plus accumulated error for the target pixel, the error being diffused to pixels adjacent the target pixel;
wherein each thresholding mask has only a limited number of threshold levels, with each different one of the plural threshold masks being provided for a different segment of the input intensity range.
0 Assignments
0 Petitions
Accused Products
Abstract
Halftoning by error diffusion, enhanced so as to reduce the presence of structural artifacts in the halftoned output while avoiding an artificial increase in halftoning image noise. Specifically, error diffusion according to the invention divides the input gray level intensity range into different segments for purposes of both thresholding and error diffusion. Different error diffusion threshold masks are applied for each respective segment, and different error diffusion weights are applied for each respective segment, with a decision being made as to whether or not to apply a different threshold mask being based on the local image gradient.
-
Citations
9 Claims
-
1. A method for halftoning image data for each of plural pixels, comprising the steps of:
-
selecting one of plural threshold masks based on intensity of the image data for a target pixel plus an accumulated error;
determining a halftone output value for the target pixel based on a comparison between a threshold in the selected threshold mask and the image data plus accumulated error for the target pixel; and
diffusing error between the halftone output value and the image data plus accumulated error for the target pixel, the error being diffused to pixels adjacent the target pixel;
wherein each thresholding mask has only a limited number of threshold levels, with each different one of the plural threshold masks being provided for a different segment of the input intensity range. - View Dependent Claims (2, 3, 4, 5, 7, 8, 9)
-
-
6. A method for halftoning image data for each of plural pixels, comprising the steps of:
-
determining a halftone output value for a target pixel based on a comparison between a threshold and the image data plus accumulated error for the target pixel;
diffusing error between the halftone output value and the image data plus accumulated error for the target pixel;
wherein error is diffused according to error diffusion weights provided for each different segment of the range of input intensities including a segment at a mid-tone segment, and wherein weights in the mid-tone segments are selected so as to decrease the tendency of the error diffusion process to form regular checkerboard patterns.
-
Specification