Patent ID: 6097846
Filing Date: 2000-08-01
Classification: G06F

Abstract:
An image processing device, in which a quantized discrete cosine transformation (DCT) coefficient is inversely-quantized and subjected to a two dimensional inverse discrete cosine transformation (IDCT) to restore each of a plurality of pixel values, and quantized DCT coefficient being obtained for each of a plurality of spatial frequencies by applying a two dimensional discrete cosine transformation (DCT) to original image data composed of said pixel values which are arranged in a matrix, and then quantizing the resultant two dimensional DCT coefficient using a quantization coefficient included in a quantization table, said device comprising:a pre-processor, said pre-processor generating a pre-processed DCT coefficient by multiplying said quantized DCT coefficient by a pre-processed coefficient, said pre-processed coefficient comprising the multiplication product of said quantization coefficient and one of a plurality of different multiplying terms corresponding to one of a plurality of cosine coefficients used in said two dimensional IDCT, each cosine coefficient comprising two cosine values multiplied by each other according to a two-dimensional IDCT equation;a post-processor which is classified into a plurality of stages in accordance with a value of said cosine coefficients, and in which a calculation corresponding to said value of said cosine coefficients is applied to said pre-processed DCT coefficient to obtain output data, the pre-processed DCT coefficient classified into one of a plurality of groups in accordance with a value of the cosine coefficients corresponding to the pre-processed DCT coefficient, each pre-processed DCT coefficient group being input to a respective one of the plurality of stages so that the calculation is applied to the pre-processed DCT coefficient; anda pixel value calculator, which classifies said plurality of pixel values into groups composed of a predetermined number of pixel values which are symmetrically disposed in said matrix and are multiplied by cosine coefficients having a same absolute value, and performs addition and subtraction operations regarding said output data included in each of said stages to restore said pixel values for each of said groups, wherein when said original image data are pixel values Pyx of an 8.times.8 pixel block, suffix ""y"" meaning a vertical position of said 8.times.8 pixel block, suffix ""x"" meaning a horizontal position of said 8.times.8 pixel block and said vertical and horizontal positions of 64 DCT coefficients Fvu, which are arranged in an 8.times.8 matrix, are indicated bv parameters ""v"" and ""u"", respectively, said pixel values being ##EQU6## said post-processor comprising a first stage in which each of said parameters ""u"" and ""v"" is 0, 4, 2, or 6, a second stage in which said parameter ""u"" is 0, 4, 2, or 6 and said parameter ""v"" is 1, 3, 5, or 7, a third stage in which said parameter ""u"" is 1, 3, 5, or 7 and said parameter ""v"" is 0, 4, 2, or 6, and a fourth stage in which each of said parameters ""u"" and ""v"" is 1, 3, 5, or 7.