Patent US 8,135,232

An image evaluation apparatus includes a pixel extraction unit, an intra-pair difference calculation unit, an inter-pair difference calculation unit and an evaluation unit. The pixel extraction unit extracts, from an input image, a pixel region including a pair of block-boundary pixels in a boundary position of coding blocks and a pair of non-block-boundary pixels in a position other than the boundary position. The intra-pair difference calculation unit calculates a difference between the extracted pair of block-boundary pixels as a first difference, and a difference between the extracted pair of non-block-boundary pixels as a second difference. The inter-pair difference calculation unit calculates a difference between the first difference and the second difference as an amount of block distortion of the extracted pixel region. The evaluation unit evaluates an amount of block distortion of the input image based on the calculated amount of block distortion of the extracted pixel region.