| 摘要 |
A method for compressing an image is provided to perform encoding more efficiently by reducing the number of coding passes of an arithmetic encoding target after a second frame so that an encoding time can be greatly reduced when the number of target bits is small. A method for compressing an image comprises the following steps of: dividing a k-numbered frame, not a first frame, of plural continuous frames into plural code blocks(S120); encoding the coding pass successively in each code block to calculate and store an inclination of the number of coding bits and distortion and increasing an order of the coding pass successively until the inclination is smaller than a reference value of a k-1 numbered frame(S141); storing the largest value and the smallest value of the inclination of all coding passes separately as the maximum value and the minimum value(S143,S144); calculating the average of the maximum value and the minimum value(S147); comparing the inclination of each coding pass and the average while increasing the coding pass order of the each code block successively until the inclination is larger than the average or the same as the average(S151,S152); determining the cutting point of each code block on the basis of the order of the coding pass(S153); encoding code blocks until the cutting point of all code blocks and storing the number of encoded bits; updating the maximum value with the average if the number of the encoded bits is smaller than the number of target bits and updating the minimum value with the average if the number of the encoded bits is larger than the number of the target bits(S157,S158a,S158b); and updating the average by repeating fourth to eighth processes and storing the updated average as the reference value of the k-numbered frame. |
