Coding method and coding apparatus for bi-level document image

A coding apparatus for bi-level document image which provides an image reading processing section, a coding processing section, a RAM, a line memory and an image inputting equipment, wherein:

• said image reading processing section, comprising:
• an image data reading means for reading bi-level document image data from said RAM;
• a storing means for making said bi-level document image data of previous line and the line before previous line read by said image data reading means store in said line memory;
• a context value generating means for generating a context value using said bi-level document image data stored in said line memory by said storing means;
• and
• a context value counting means for counting the number of appearance times of a context value based on said the context value generated by said context value generating means and the values of said bi-level document image data stored by said storing means,
• said coding processing section, comprising:
• a normal coding means for implementing coding by a normal JBIG algorithm;
• a high speed coding means for implementing coding by using the values of the context value counted by said context value counting means in high speed;
• and
• a coding processing deciding means for deciding to use either coding processing of said normal coding means or said high speed coding means,
• wherein said coding apparatus for bi-level document image detects sequential white areas existing in said bi-level document image data and codes a large amount of said sequential white areas using said high speed coding means.

A coding apparatus for a bi-level document image comprising:

• an image data reading means for reading bi-level document image data from a first memory;
• a storing means for storing a first line of said bi-level document image data and a second line of bi-level document image data in a second memory;
• a context value generating means for generating a context value using said bi-level document image data stored in said second memory
• a context value counting means for counting the number of context values generated by said context value generating means and the values of said bi-level document image data stored by said storing means,
• a normal coding means for implementing coding by a normal JBIG algorithm;
• a high speed coding means for implementing-coding by using the context values counted by said context value counting means;
• and
• a coding-processing deciding means for deciding to use either said normal coding means or said high speed coding means,
• wherein said coding apparatus detects sequential white areas existing in said bi-level document image data and codes said sequential white areas using said high speed coding means.

A method of coding a bi-level document image comprising:

• reading bi-level document image data from a first memory;
• storing a first line of bi-level document image data and a second line of bi-level document image data in a second memory;
• generating a context value using said bi-level document image data stored in said second memory;
• counting a number of context values generated;
• counting values of said bi-level document image data;
• implementing coding by a normal JBIG algorithm;
• implementing coding by using said context values counted;
• detecting sequential white areas existing in said bi-level document image data;
• and
• deciding to use coding by said normal JBIG algorithm or coding by said context values counted,
• wherein said sequential white areas existing in said bi-level document image data are coded by said context values counted.