Edge enhancement method for halftone image
View Patent ↗A method for enhancing the edge of a halftone image includes steps of: forming an analysis window with a central pixel and neighboring pixels; quantifying the pixels to get a halftone table; assigning a designated value to each pixel for generating a halftone result; and comparing the halftone result with an edge enhancement table. The edge enhancement table includes a plurality of dotting commands and a plurality of dot tables. The dot tables correspond to the dotting commands so that when a dot table is conformed to the halftone result, a correspondent adjustment of halftone table is taken.
1. A method for enhancing edge of a halftone image, comprising steps of:
performing the following steps using an image processing device;
forming an analysis window with a pixel as a central pixel; the analysis window comprising the central pixel and neighboring pixels;
quantifying the pixels to get a halftone table;
assigning a designated value to each pixel for generating a halftone result;
comparing the halftone result with an edge enhancement table having a plurality of dotting commands and a plurality of dot tables; the dot tables correspond to one of the dotting commands; and
executing a halftone table adjustment when one of the dot tables is conformed to the halftone result; the adjustment comprising steps of:
obtaining correspondent dotting commands according to the conformed dot table;
calculating a plurality of adjustment values for the pixels according to the dotting commands and an error diffusion process; and
adjusting the halftone table according to the adjustment values.
2. The method for enhancing edge of a halftone image according to claim 1 wherein the halftone table comprises a plurality of grayscale values of the pixels.
3. The method for enhancing edge of a halftone image according to claim 1 wherein the step of adjusting the halftone table according to the adjustment values further comprises a step of adding the grayscale values with the adjustment values of same pixels.
4. The method for enhancing edge of a halftone image according to claim 1 wherein the dotting command is to define a representative dot position for the pixels.
5. The method for enhancing edge of a halftone image according to claim 1 wherein the dot table has a same size as that of the analysis window.
6. The method for enhancing edge of a halftone image according to claim 1 wherein the designated value is a one-bit value.
7. A method for enhancing edge of a colored halftone image, comprising steps of:
performing the following steps using an image processing device;
separating an edge image into four color planes;
performing a halftone diffusion process to the each color plane; the process comprises steps of:
forming an analysis window with a pixel as a central pixel; the analysis window
comprises the central pixel and neighboring pixels;
quantifying the pixels to get a halftone table;
assigning a designated value to each pixel for generating a halftone result;
comparing the halftone result with an edge enhancement table having a plurality of dotting commands and a plurality of dot tables; the dot tables correspond to one of the dotting commands; and
executing a halftone table adjustment when one of the dot tables is conformed to the halftone result; the adjustment comprises steps of:
obtaining correspondent dotting commands according to the conformed dot table;
calculating a plurality of adjustment values for the pixels according to the dotting commands and an error diffusion process; and
adjusting the halftone table according to the adjustment values; and
comparing the dot table and correspondent dotting commands of each color plane with a dotting command lookup table to obtain practical dotting commands for the pixels.
8. The method for enhancing edge of a halftone image according to claim 7 wherein the halftone table comprises a plurality of grayscale values of the pixels.
9. The method for enhancing edge of a halftone image according to claim 7 wherein the step of adjusting the halftone table according to the adjustment values further comprises a step of adding the grayscale values with the adjustment values of same pixels.
10. The method for enhancing edge of a halftone image according to claim 7 wherein the dotting command is to define a representative dot position for the pixels.
11. The method for enhancing edge of a halftone image according to claim 7 wherein the dot table has a same size as that of the analysis window.
12. The method for enhancing edge of a halftone image according to claim 7 wherein the dotting command lookup table comprises the contents of conformable dotting command from no conformation to all conformations of color planes, combinations of dotting commands, and a plurality of practical dotting commands corresponding to the contents.
13. The method for enhancing edge of a halftone image according to claim 7 wherein the designated value is a one-bit value.