Image quality evaluation is an important field of image processing

but classical image quality evaluation method can not represent knowledge perceived by human eyes.In this paper

we propose that in the case of distorted image processing

the perceptive information of image is increasing while Shannon information is decreased. We define some perceptive parameters

such as the change of texture character

histogram

frequency spectrum

knowledge of image

and we calculate the perceptive information using sigmoid function.The results show that the perceptive information is valid and reasonable.