Font and Line Art Rendering for Multi-Bit Output Devices

• US 20090195795A1
• Filed: 01/31/2008
• Published: 08/06/2009
• Est. Priority Date: 01/31/2008
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Chang, Ching-Wei
• Granted Patent: US 8,059,311 B2
• Time in Patent Office: Days
• US Class Current: 358/1.9
• CPC Class Codes: H04N 1/40087 Multi-toning, i.e. converting a continuous-tone signal for reproduction with more than two discrete brightnesses or optical densities, e.g. dots of grey and black inks on white paper
• CPC Class Codes: H04N 1/52 Circuits or arrangements for halftone screening

Abstract

Multilevel color page image rendering via multi-bit output devices including the rounding of tone levels, dual tone scan patterns and the selecting or generating of halftone cells and electrophotography engines and image processors for rendering multilevel tone density objects such as font and line art.

Claims

1. A method of multilevel tone density rendering comprising:

determining a maximum tone density level of a color component of an object wherein the object data comprises a plurality of pixels and the object data is characterized by at least one color component;

snapping the determined maximum tone density level based on a quantization level of a rendering device; and

rendering the plurality of pixels of the object with the color component at the snapped tone density level.

2. The method of multilevel tone density rendering as claimed in claim 1 further comprising:

determining a median tone density level of a color component of the plurality of pixels of the object data;

selecting or generating, based on the determined median tone density level, a halftone pattern having pixels characterized by the color component of the determined median tone density, and wherein the halftone pattern pixels are further characterized by a tone density level based on the determined median tone density level; and

wherein the step of rendering the plurality of pixels of the object with the color component having the snapped tone density further comprises rendering a portion of the plurality of pixels of the object with the color component of the determined median tone density according to the selected or generated halftone pattern.

3. The method of multilevel tone density rendering as claimed in claim 2 wherein the rendered tone density of the color component having the determined median tone density level is associated with the selected or generated halftone pattern.

4. The method of multilevel tone density rendering as claimed in claim 1 further comprising:

testing whether the snapped tone density level is not supported by the rendering device, and if the snapped tone density level is not supported by the rendering device, then;

determining a first device-supported tone density level greater than the snapped tone density level and a second device-supported tone density level less than the determined maximum tone density level; and

rendering the object via an application of one or more scan lines comprising the first device-supported tone density level greater than the snapped tone density level and the second device-supported tone density level less than the snapped tone density level.

5. The method of multilevel tone density rendering as claimed in claim 1 further comprising:

testing of the object data characterized by three color components, each color component associated with a tone density level, whether the tone density level of each of the three color components of the object data are within a test range of tone density levels, relative to one another, and if true;

(a) determining a tone density level of a black component based on the three color density levels, and

(b) assigning the determined tone density level of the black component as the determined maximum tone density level of a color component of the object comprising a plurality of pixels characterized by at least one color component.

6. The method of multilevel tone density rendering as claimed in claim 5 further comprising:

testing whether the snapped tone density level is not supported by the rendering device, and if not supported by the rendering device, then;

determining a first device-supported tone density level greater than the determined maximum tone density level and a second device-supported tone density level less than the determined maximum tone density level; and

rendering the object via an application of one or more scan lines comprising the first device-supported tone density level greater than the snapped tone density level and the second device-supported tone density level less than the snapped tone density level.

7. A method of multilevel tone density rendering comprising:

determining a maximum tone density level of a color component of an object comprising a plurality of pixels characterized by at least one color component;

testing whether the determined maximum tone density level is not supported by the rendering device, and if not supported by the rendering device, then;

determining a first device-supported tone density level greater than the determined maximum tone density level and a second device-supported tone density level less than the determined maximum tone density level; and

rendering the object via an application of one or more scan lines comprising the first device-supported tone density level and the second device-supported tone density level less than the snapped tone density level.

8. The method of multilevel tone density rendering as claimed in claim 7 further comprising:

determining a median tone density level of a color component of the plurality of pixels of the object;

selecting or generating, based on the determined median tone density level, a halftone pattern having pixels characterized by the color component having the determined median tone density, wherein the halftone pattern pixels are characterized by a tone density level based on the determined median tone density level; and

wherein the step of rendering pixels of the object with the color component having the snapped tone density further comprises rendering a portion of the pixels of the object with the color component having the determined median tone density according to the selected or generated halftone pattern.

9. The method of multilevel tone density rendering as claimed in claim 8 wherein the rendered tone density of the color component having the determined median tone density level is associated with the selected or generated halftone pattern.

10. The method of multilevel tone density rendering as claimed in claim 8 further comprising:

testing of the object data characterized by three color components, each color component associated with a tone density level, whether the tone density level of each of the three color components of the object data are within a test range of tone density levels, relative to one another, and if true;

(a) determining a tone density level of a black component based on the three color density levels, and

(b) assigning the determined tone density level of the black component as the determined maximum tone density level of a color component of the object comprising a plurality of pixels characterized by at least one color component.

11. An image processor operative to render multilevel tone density objects, the image processor comprising:

a rendering subsystem and

a processing module comprising a processor and addressable memory, adapted to receive object data comprising three color components, each color component having an associated tone density level, the processing module further comprising;

a three-color comparator adapted to output the largest of the three tone density levels and the median of the three tone density levels;

a gray level snapping module adapted to quantize the largest of the three tone density levels;

a halftone generator adapted to provide a halftone cell pattern based on the median tone density level; and

a halftoner adapted to render the color component associated with the median tone density level according to the generated halftone cell pattern.

12. The image processor of claim 11 wherein the processing module further comprises:

a scan line toner module adapted to receive at least one of the snapped tone density level or the largest tone density as an input level, and further adapted to determine a first device-supported tone density level greater than the input level and a second device-supported tone density level less than the input level and render the color component associated with the largest tone density of the object via an application of one or more scan lines comprising the first device-supported tone density level greater than the largest tone density level and the second device-supported tone density level less than the largest tone density level.

13. A printing apparatus for rendering a color image having color pixels on a surface comprising:

an image processor operative to render multilevel tone density objects, the image processor comprising a processing module comprising a processor and addressable memory, adapted to receive object data comprising three color components, each color component having an associated tone density level, the processing module further comprising;

a three-color comparator adapted to output the largest of the three tone density levels and the median of the three tone density levels;

a gray level snapping module adapted to quantize the largest of the three tone density levels;

a halftone generator adapted to provide a halftone cell pattern based on the median tone density level; and

a halftoner adapted to render the color component associated with the median tone density level according to the generated halftone cell pattern.

14. The printing apparatus of claim 13 wherein the processing module further comprises:

a scan line toner module adapted to receive at least one of a snapped tone density level or the largest tone density as an input level, and further adapted to determine a first device-supported tone density level greater than the input level and a second device-supported tone density level less than the input level and render the color component associated with the largest tone density of the object via an application of one or more scan lines comprising the first device-supported tone density level greater than the largest tone density level and the second device-supported tone density level less than the largest tone density level.