Color display system

A method of displaying an image having a plurality of pixels arranged in a plurality of lines, said method comprising the steps of:

• inputting colour information of each of a plurality of pixels in an analogue format;
• converting the colour information from the analogue format to a corresponding digital format for each said pixel;
• halftoning said digital information of each said pixel using a plurality of said pixels to produce output colour information;
• dividing each line of said image into a plurality of groups of said pixels and determining a corresponding signature for each of said groups, each said signature being calculated from said pixels within said group;
• determining those portions of the colour information that have changed by comparing a current signature of said groups with a previous signature of the corresponding group;
• and
• outputting said output colour information corresponding to at least those groups where it has been determined that said colour information has changed.

An arrangement for displaying video images, said arrangement comprising:

• signal means for providing a video input signal having colour information contained therein capable of producing a continuous tone image using colours obtained in a first set having a first plurality of colours;
• a display device capable of displaying colours in a second set having a substantially limited second plurality of colours;
• and
• display converting means for receiving said input signal and manipulating said colour information using halftoning and signature comparison of groups of pixels to provide converted colour information which, when input to said display device, provides a substantially continuous tone image using said second set of colours,
• wherein said input signal is in an analogue format and said display converting means includes:
• analogue input means adapted to receive said analogue input signal representing a continuous tone image to be displayed;
• converter means adapted to receive analogue colour information from said analogue input signal and to produce a corresponding digital representation of said analogue colour information,
• halftoning means adapted to receive the digital representation from said converting means and to produce a corresponding halftoned current output pixel value, for each one of a plurality of pixels of said display device, from said digital representation of said analogue colour information;
• frame store means adapted to store said current output pixel values from said halftoning means;
• line update means adapted to receive said output pixel values from said halftoning means and to further receive corresponding previous output pixel values from said frame store means and to determine by signature comparison if a group of pixels values have changed so as to require changing on said display device;
• and
• frame store controlling means adapted to receive information from said line update means as to whether a group of pixels requires changing and for causing said frame store means to write out said current output pixel values corresponding to at least said group of pixels to said display device, wherein said halftoning means is configured to error diffuse a plurality of pixels of an image to determine said current output pixel value, and said signature comparison determines a signature for each said group of pixels by calculating a weighted summation of said pixels within said group and comparing a current signature with a previous signature for the corresponding group to determine an amount of change, said changing of output pixels occurring when the amount of change of said signatures exceeds a predetermined value.

An arrangement for displaying video images, said arrangement comprising:

• signal means for providing a video input signal having colour information contained therein capable of producing a continuous tone image using colours obtained in a first set having a first plurality of colours;
• a display device capable of displaying colours in a second set having a substantially limited second plurality of colours, and
• display converting means for receiving said input signal and manipulating said colour information using halftoning and signature comparison of groups of pixels to provide converted colour information which, when input to said display device provides a substantially continuous tone image using said second set of colours,
• wherein said signal is in a digital format and provides a digital representation of said colours in said first set,
• wherein said display converting means includes:
• halftoning means adapted to receive said digital representation from said converting means to produce a corresponding halftoned current output pixel value, for each one of said plurality of pixels of said display device, from said digital representation of said colour information;
• frame store means adapted to store said current output pixel values from said halftoning means;
• line update means adapted to receive said output pixel values from said halftoning means and to further receive corresponding previous output pixel values from said frame store means and to determine by signature comparison if a group of pixels values have changed so as to require changing on said display device;
• and
• frame store controlling means for receiving information from said line update means as to whether a group of pixels requires changing and for causing said frame store means to write out said current output pixel values corresponding to at least said group of pixels to said display device,
• wherein said halftoning means is configured to error diffuse a plurality of pixels of an image to determine said current output pixel value, and said signature comparison determines a signature of each said group of pixels by calculating a weighted summation of said pixels within said group and comparing a current signature with a previous signature for the corresponding group to determine an amount of change, said changing of output pixels occurring when the amount of change of said signatures exceeds a predetermined value.