Irreversible compression apparatus, and method and program for controlling operation of same

摘要

A compressed image, for which a desired SSIM value is obtained, is acquired when irreversible compression is performed. Specifically, a quadratic curve G2 is defined. Next, a compression ratio P4 is calculated. An image is irreversibly compressed at the compression ratio P4, the compressed image is decoded and an SSIM value S5 is calculated. If the calculated SSIM value S5 is outside an allowable range of the target SSIM value, then the quadratic curve G2 is corrected in such a manner that it will pass through an intersection C4 between the compression ratio P4 and the SSIM value S5, whereby a quadratic curve G3 is obtained.

主权项

1. An irreversible compression apparatus for irreversibly compressing image data, comprising:
an irreversible compression control device for controlling the irreversible compression apparatus, based upon a curve representing a relationship between compression ratio of irreversible compression and image quality of image data that has been irreversibly compressed, in such a manner that the image will be irreversibly compressed at a compression ratio that will result in a desired image quality; an image quality calculating device for calculating the image quality of the image data irreversibly compressed under control exercised by said irreversible compression control device; a curve correcting device for correcting the curve so as to satisfy a relationship between the compression ratio, which is used in control of the irreversible compression apparatus by said irreversible compression control device, and the image quality calculated by said image quality calculating device; and a control device for controlling said irreversible compression control device, said image quality calculating device and said curve correcting device in such a manner that control by said irreversible compression control device, calculation of image quality by said image quality calculating device and correction of the curve by said curve correcting device are repeated until the image quality calculated by said image quality calculating device attains the desired image quality.