Coding method and apparatus
AssigneeNippon Telegraph and Telephone Corporation
InventorsHiroshi Ochi, Makoto Kobayashi, Hisashi Ibaraki, Tetsuji Yamamoto
Life of this patent
Estimating the term…
Abstract
A coding method includes the steps of dividing an image into a plurality of blocks each consisting of a plurality of picture elements, dividing gray scale information of each intrablock picture element into three components, i.e, (1) a reference level representing a position of a signal level of an intrablock picture element in a whole dynamic range of gray scale representation, (2) a level difference representing a distribution range of the signal levels of the intrablock picture elements, and (3) a level designating signal representing a level of each intrablock picture element within the distribution range, and independently coding the three components.
Claims25
A coding method comprising the steps of
- dividing an image into a plurality of blocks each consisting of a plurality of intrablock picture elements,
- dividing gray scale information of each intrablock picture element into three components:
- (1) a reference level representing a position of a signal level of an intrablock picture element in a whole dynamic range of gray scale representation;
- (2) a level difference representing a distribution range of the signal levels of the intrablock picture elements;
- and
- (3) a level designating signal representing a level of each intrablock picture element within the distribution range, and
- independently coding the three components.
A coding apparatus comprising:
- a memory for dividing an image into blocks each consisting of a plurality of intrablock picture elements;
- a comparator for calculating maximum and minimum values of a signal level of each intrablock picture element in units of blocks;
- an arithmetic circuit for setting quantization levels between the maximum and minimum values;
- a first coding circuit for coding a reference level derived from the signal level of each intrablock picture element in units of blocks;
- a second coding circuit for coding a level difference derived from the signal level of each intrablock picture element;
- and
- a third coding circuit for coding a level designating signal representing a correspondence between a corresponding picture element and one of the quantization levels.
A coding apparatus comprising:
- means for dividing an image into blocks each consisting of a plurality of intrablock picture elements;
- means for calculating and storing a maximum value of the signal level of each intrablock picture element in units of blocks;
- means for calculating and storing a minimum value of the signal level of each intrablock picture element in units of blocks;
- first coding means for setting a reference level in units of blocks based on the signal level of each intrablock picture element and coding the reference level;
- second coding means for setting a level difference in units of blocks based on the signal level of each intrablock picture element;
- and
- third coding means for setting quantization levels between the maximum and minimum values in units of blocks, discriminating a corresponding one of the quantization levels for each intrablock picture element, and coding a level designating signal representing the discriminated quantization level.
An apparatus for decoding a time-serial code string obtained by independently coding three components of gray scale information of each intrablock picture element, the gray scale information consisting of (1) a reference level representing a position of a signal level of an intrablock picture element in a whole dynamic range of gray scale representation, (2) a level difference representing a distribution range of the signal levels of the intrablock picture elements, and (3) a level designating signal representing a level of each intrablock picture element within the distribution range, comprising:
- coding control means for separating the code string into the three components and independently outputting the three components;
- first decoding means for decoding a coded reference level output from said code control means;
- first storage means for storing a reference level signal decoded by said first decoding means;
- second decoding means for decoding the coded level difference output from said code control means;
- second storage means for storing a level difference signal decoded by said second decoding means;
- third decoding means for decoding a coded level designating signal output from said code control means;
- signal converting means for converting the reference level signal stored in said first storage means according to the level designating signal decoded by said third decoding means;
- level number discriminating means for discriminating the number of levels represented by the level designating signals;
- and
- means for controlling a content of a signal converted by said signal converting means according to an output from said level number discriminating means.
An apparatus for decoding a time-serial code string obtained by independently coding three components of gray scale information of each intrablock picture element, the gray scale information consisting of (1) a reference level representing a position of a signal level of an intrablock picture element in a whole dynamic range of gray scale representation, (2) a level difference representing a distribution range of the signal levels of the intrablock picture elements, and (3) a level designating signal representing a level of each intrablock picture element within the distribution range, comprising:
- coding control means for separating the code string into the three components and independently outputting the three components;
- first decoding means for decoding a coded reference level output from said code control means;
- second decoding means for decoding a coded level difference output from said code control means;
- third decoding means for decoding a coded level designating signal output from said code control means;
- signal generating means for generating quantization levels according to a reference level signal decoded by said first decoding means and a level difference signal decoded by said second decoding means;
- and
- means for selecting one of signals output from said signal generating means in response to the level designating signal decoded by said third decoding means.
Dependencies are inferred from the claim text.