Image processor using both dither and error diffusion to produce halftone images with less flicker and patterns

An image processing device having processors, for red, green, and blue, respectively, said processors receiving n-bit-quantized red, green, and blue signals, which each represent an integer in the range of 0 to 2.sup.n-1, respectively, and carry out an error distribution operation to artificially display many shades on a display which is originally capable of displaying m-bit shades (m<n) equal to or less than 2.sup.m for each of the red, green, and blue, wherein each of said processors comprises:

• a multiplier for multiplying an input signal by a multiplication coefficient;
• a first register for storing the multiplication coefficients;
• a first selector for selecting a proper one of the multiplication coefficients stored in said first register;
• an adder disposed between said multiplier and an error distribution unit, to add an addition coefficient to an output of said multiplier;
• a second register for storing the addition coefficients;
• and
• a second selector for selecting a proper one of the addition coefficients stored in said second register, each of said processors separating the input signal into display data and error data along a bit boundary, to carry out the error distribution operation and provide a smooth display characteristic for the entire range of input shades.

An image processing device comprising:

• an error distribution unit for carrying out an error distribution operation to artificially increase the number of shades to be displayed on a display;
• and
• a dither processor to convert error data, which easily cause a state transition, into data that hardly cause the state transition, to thereby suppress flicker;
• said dither processor including a dither table for storing dither values to be applied to the input signal that easily causes flicker, and a dithering unit for adding or subtracting the output of said dither table to or from the input signal.

A semiconductor integrated circuit comprising:

• a dither pattern generator for storing a plurality of dither patterns in advance and receiving an input image signal and a control signal output from a timing generator in response to input control signals;
• an adder for receiving the input image signal and a pattern signal from said dither pattern generator;
• and
• an error distribution unit for carrying out an error distribution operation on the output of said adder in response to the control signal from said timing generator.

A display panel comprising:

• a timing generator for providing control signals in response to input control signals;
• a dither pattern generator for storing a plurality of dither patterns in advance and receiving the control signal from said timing generator as well as an input image signal;
• an adder for receiving the input image signal and a pattern signal from said dither pattern generator;
• an error distribution unit for carrying out an error distribution operation on the output of said adder in response to the control signal from said timing generator;
• and
• a display having a two-dimensional matrix of pixels to be driven according to the output of said timing generator and the output of said error distribution unit.

A plasma display panel, having an image processing device, for displaying a shade as an optional combination of subframes having different lighting periods according to weighted bits, said image processing device including processors for red, green, and blue, respectively, said processors receiving n-bit-quantized red, green, and blue signals, which represent each an integer in the range of 0 to 2.sup.n-1, respectively, and carrying out an error distribution operation to artificially display many shades on a display which is originally capable of displaying m-bit shades (m-n) equal to or less than 2.sup.m for each of the red, green, and blue, wherein each of said processors comprises:

• a multiplier for multiplying an input signal by a multiplication coefficient;
• a first register for storing the multiplication coefficients;
• a first selector for selecting a proper one of the multiplication coefficients stored in said first register;
• an adder disposed between said multiplier and said error distribution unit, to add an addition coefficient to an output of said multiplier;
• a second register for storing the addition coefficients;
• and
• a second selector for selecting a proper one of the addition coefficients stored in said second register, each of said processors separating the input signal into display data and error data along a bit boundary, to carry out the error distribution operation and provide a smooth display characteristic for the entire range of input shades.

A plasma display panel having an image processing device, for displaying a shade as an optional combination of subframes having different lighting periods according to weighted bits, wherein said image processing device comprises:

• an error distribution unit for carrying out an error distribution operation to artificially increase the number of shades to be displayed on a display;
• and
• a dither processor to convert error data, which easily cause a state transition, into data that hardly cause the state transition, to thereby suppress flicker;
• said dither processor including a dither table for storing dither values to be applied to the input signal that easily causes flicker, and a dithering unit for adding or subtracting the output of said dither table to or from the input signal.

A method of displaying a halftone image on a display having a plurality of pixels arranged in a two-dimensional matrix configuration, comprising the steps of:

• inputting a halftone image data representing a shade and being constituted for each pixel;
• adding a dither pattern including two alternate thresholds of opposite polarities to the input halftone image data appropriate therefor;
• and
• carrying out an error distribution operation on said dither-pattern-added input halftone image data.

A method of displaying a halftone image on a display having a plurality of pixels arranged in a two-dimensional matrix configuration, comprising the steps of:

• inputting a halftone image data representing a shade and being constituted for each pixel;
• adding a dither pattern to the input halftone image data appropriate therefor, the dither pattern being selected from a plurality of different types of dither patterns and used in accordance with the input halftone image data at a specific time interval;
• and
• carrying out an error distribution operation on said dither-pattern-added input halftone image data.

A method of displaying a halftone image on a display having a plurality of pixels arranged in a two-dimensional matrix configuration, comprising the steps of:

• inputting a halftone image data representing a shade and being constituted for each pixel;
• adding a dither pattern to the input halftone image data appropriate therefor, the dither pattern being selected from a plurality of different types of dither patterns and used in accordance with the input halftone image data at a plurality of spatial positions;
• and
• carrying out an error distribution operation on said dither-pattern-added input halftone image data.

A method of displaying a halftone image on a display having a plurality of pixels arranged in a two-dimensional matrix configuration, for applying to a halftone image data representing the shade just before a shade of (4n-1), where n is a natural number, comprising the steps of;

• inputting a halftone image data representing a shade and being constituted for each pixel;
• adding a dither pattern to the input halftone image data appropriate therefor;
• and
• carrying out an error distribution operation on said dither-pattern-added input halftone image data.