Image compression apparatus, image expansion apparatus, image forming apparatus, image compression method, image expansion method and storage medium

An image expansion apparatus for restoring coded data into image data, comprising:

• a first processing part configured to analyze the coded data and to output output information;
• a second processing part configured to generate a run length based on the output information of said first processing part;
• and
• a third processing part configured to generate the image data, based on the run length generated by said second processing part and the output information of said first processing part.

An image compression method for compressing image data by carrying out a parallel processing for every image pattern made up of a plurality of bits, comprising:

• a first processing step calculating a run length of the image data and a repetition number of the run length;
• a second processing step coding the run length and the repetition number calculated by said first processing step;
• and
• a third processing step predicting whether or not a code length of a code which is to be coded by said second processing step exceeds a predetermined threshold value, based on the run length and the repetition number by said first processing step,
• said second processing step carrying out a pass coding to output the image pattern when said third processing part predicts that the code length exceeds the predetermined threshold value.

An image expansion method for restoring coded data into image data, comprising:

• a first processing step analyzing the coded data and outputting output information;
• a second processing step generating a run length based on the output information of said first processing step;
• and
• a third processing step generating the image data, based on the run length generated by said second processing step and the output information of said first processing step.

A computer-readable storage medium which stores a program for causing a computer to compress image data by carrying out a parallel processing for every image pattern made up of a plurality of bits, said program comprising:

• a first processing procedure causing the computer to calculate a run length of the image data and a repetition number of the run length;
• a second processing procedure causing the computer to code the run length and the repetition number calculated by said first processing procedure;
• and
• a third processing procedure causing the computer to predict whether or not a code length of a code which is to be coded by said second processing procedure exceeds a predetermined threshold value, based on the run length and the repetition number calculated by said first processing procedure,
• said second processing procedure causing the computer to carry out a pass coding to output the image pattern when said third processing procedure predicts that the code length exceeds the predetermined threshold value.

A computer-readable storage medium which stores a program for causing a computer to restore coded data into image data, said program comprising:

• a first processing procedure causing the computer to analyze the coded data and to output output information;
• a second processing procedure causing the computer to generate a run length based on the output information of said first processing procedure;
• and
• a third processing procedure causing the computer to generate the image data, based on the run length generated by said second processing procedure and the output information of said first processing procedure.