IMAGE COMPRESSING AND EXPANDING DEVICE

摘要

PROBLEM TO BE SOLVED: To record and reproduce images at an arbitrary set compression factor. SOLUTION: In an image compressing device 10, a DCT computing section 11, an area segmenting and filtering section 12, a quantizing section 13, and a Haffman coding section 14 are provided. The DCT computing section 11 converts image data into DCT coefficients through DCT computation. The area segmenting and filtering section 12 compares the absolute values of the DCT coefficients with a threshold m related to a compression factor in a zigzag scanning direction in the block of the DCT coefficients. When the absolute values continuously become smaller than the threshold m, the section 12 uses one of the DCT coefficients as a boundary DCT coefficient and changes the values of the DCT coefficient preceding the boundary DCT coefficient in the zigzag scanning direction to zero. The quantizing section 13 converts the DCT coefficients into quantized DCT coefficients by quantizing the DCT coefficients. The Haffman coding section 14 generates compressed image data by encoding the quantized DCT coefficients into Haffman codes.