Patent ID: 6226445
Filing Date: 2001-05-01
Classification: H04N

Abstract:
An image compression device, by which compressed image data is recorded in a recording medium, having a compressed image data recording area, in which said compressed image data is stored, and a first table recording area, which is accessed in a usual expansion process, a second table recording area which is not accessed in the usual expansion process, and an information recording area, in which security information is recorded, said image compression device comprising:a two-dimensional discrete cosine transformation (two-dimensional DCT) processor that processes original image data to obtain a DCT coefficient for each spatial frequency;a quantization processor that quantizes said DCT coefficient for each spatial frequency by a normal mode quantization table, which is used in said usual expansion process, to obtain quantized DCT coefficients;an encoding processor that encodes said quantized DCT coefficients to obtain compressed image data;a compressed image recording processor that records said compressed image data in said compressed image data recording area;a first table recording processor that records a security mode quantization table, which is different from the normal mode quantization table and is used when dequantizing the quantized DCT coefficients in a security mode for reproducing an image having a lower quality than an original image, in said first table recording area; anda second table recording processor that records said normal mode quantization table in a second table recording area.