Image compression method and device

The invention discloses an image compression method and device. The method comprises the following steps of adopting an initial quality factor for obtaining an input image; computing an objective quality assessment score of the input image after double compression processing according to the initial quality factor and a preset minimum quality factor; carrying out adaptive adjustment on the quality factor of the input image according to the objective quality assessment score, a preset objective quality assessment score of the image, which is corresponding to the type of the input image, and a preset rule, stopping a compression process until the objective quality assessment score for image compression meets a preset threshold range, and computing to obtain a first quality factor; carrying out fine tuning on the first quality factor according to subjective image quality factor priori knowledge obtained based on mass data knowledge, and determining a second quality factor; and carrying out compression processing