METHOD FOR SYNTHESIZING JPEG IMAGES AND METHOD AND APPARATUS FOR SUPERIMPOSING OSD INFORMATION ONTO JPEG IMAGE

摘要

A method for synthesizing JPEG image and method and apparatus for superimposing OSD information onto JPEG image. The method for synthesizing JPEG image comprises performing entropy decoding, AC/DC coefficient decoding, inverse DC prediction and inverse quantization on the JPEG bit stream of a first image and a second image to obtain DCT coefficients; synthesizing the DCT coefficients in the order of JPEG raster scan according to the image stitching mode; and performing quantization, DC prediction, AC/DC coefficient encoding and entropy encoding on the synthesized DCT coefficients to form a bit stream of a synthesized image. For superimposing OSD information, only the region of the image to be superimposed is transformed by an IDCT. The OSD information is superimposed in the YUV plane and converted to DCT coefficients by DCT. The DCT coefficients superimposed with OSD information are synthesized with the DCT coefficients of non-superimposed region of the image.