Halftoning method and apparatus using templates indexed by code
View Patent ↗Techniques are provided that use one or more templates to improve the printing of non-saturated colored text and lines. Such templates are predetermined, fixed patterns which can be indexed or looked up via a code word with a fewer number of bits than in the corresponding template. Thus, such templates are used to increase the resolution or effective resolution of a display. In an embodiment, each template location represents a 4×4 region of binary pixels. The number of possibilities of template values is 2^(4*4) or 65,536. However, in accordance with an embodiment, only 256 of these 65,536 templates are available and are indexed by an 8 bit contone video value.
1. A computer-implemented method for halftoning, comprising the steps of:
dividing a 1/600 th square within a 600 dpi pixel into four quadrants, each quadrant having eight bits;
for each quadrant, using two bits of the eight bits for programming a contone level, said contone level being from the set of: zero, one, two, and three;
setting a tag bit for the 600 dpi pixel to a particular template from a set of templates; and
using the particular template as two bits per pixel at 1200 dpi;
wherein the particular template requires not using any of its eight bits for contone or any of its eight bits for representing a binary four-by-four square within a 600 dpi pixel; and
wherein at least one of the steps is performed by a processor.
2. The method of claim 1 , wherein the two bits per pixel at 1200 dpi are from a set comprising:
a first code to represent a 2-by-2 matrix of binary pixels in the top left corner with no saturation;
a second code to represent a 2-by-2 matrix of binary pixels in the top right corner having full saturation in the two rightmost pixels;
a third code to represent a 2-by-2 matrix of binary pixels at the bottom left corner with full saturation in the two leftmost pixels; and
a fourth code to represent to a 2-by-2 matrix of binary pixels at the bottom right corner with full saturation in all four of the pixels.
3. An apparatus for halftoning, comprising:
a dividing processor configured for dividing a 1/600 th square within a 600 dpi pixel into four quadrants, each quadrant having eight bits;
a processor configured for using, for each quadrant, two bits of the eight bits for programming a contone level, said contone level being from the set of: zero, one, two, and three;
a setting processor configured for setting a tag bit for the 600 dpi pixel to a particular template from a set of templates; and
a processor configured for using the particular template as two bits per pixel at 1200 dpi;
wherein the particular template requires not using any of its eight bits for contone or any of its eight bits for representing a binary four-by-four square within a 600 dpi pixel; and
wherein at least one of the steps is performed by a processor.
4. The apparatus of claim 3 , wherein the two bits per pixel at 1200 dpi are from a set comprising:
a first code to represent a 2-by-2 matrix of binary pixels in the top left corner with no saturation;
a second code to represent a 2-by-2 matrix of binary pixels in the top right corner having full saturation in the two rightmost pixels;
a third code to represent a 2-by-2 matrix of binary pixels at the bottom left corner with full saturation in the two leftmost pixels; and
a fourth code to represent to a 2-by-2 matrix of binary pixels at the bottom right corner with full saturation in all four of the pixels.
5. A non-transitory computer readable medium having stored thereon a computer program for halftoning, said computer program comprising a program code which, when executed by a processor, performs the steps of:
dividing a 1/600 th square within a 600 dpi pixel into four quadrants, each quadrant having eight bits;
for each quadrant, using two bits of the eight bits for programming a contone level, said contone level being from the set of: zero, one, two, and three;
setting a tag bit for the 600 dpi pixel to a particular template from a set of templates; and
using the particular template as two bits per pixel at 1200 dpi;
wherein the particular template requires not using any of its eight bits for contone or any of its eight bits for representing a binary four-by-four square within a 600 dpi pixel.
6. The non-transitory computer readable medium of claim 5 , wherein the two bits per pixel at 1200 dpi are from a set comprising:
a first code to represent a 2-by-2 matrix of binary pixels in the top left corner with no saturation;
a second code to represent a 2-by-2 matrix of binary pixels in the top right corner having full saturation in the two rightmost pixels;
a third code to represent a 2-by-2 matrix of binary pixels at the bottom left corner with full saturation in the two leftmost pixels; and
a fourth code to represent to a 2-by-2 matrix of binary pixels at the bottom right corner with full saturation in all four of the pixels.