Patent ID: 8184711

Claim:
An image processing device comprising: an orthogonal transformation section that generates a transformation coefficient by performing orthogonal transformation for image data, and performs, in terms of correlation with inverse orthogonal transformation, scale change on a value of a coefficient element constituting the transformation coefficient with a plurality of scales; a division factor calculation section that calculates a plurality of division factors by multiplying the scale change by a decoding factor calculated based on a plurality of quantization factors possibly used during decoding; a sum calculation section that calculates, for each detection unit, the sum of evaluation values based on a residue obtained as a result of dividing the element of the transformation coefficient by a plurality of the division factors; and a quantization factor detection section that compares correlations of the sum of the evaluation values with a plurality of the division factors, and detects, based on the division factor whose sum of the evaluation values is a minimum value, the quantization factor used in the previous process of encoding the image data.