The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 23, 2000
Filed:
Sep. 11, 1997
Olagappan Manickam, Cupertino, CA (US);
Jonathan E DeVito, Belmont, CA (US);
Radovan V Krtolica, Los Gatos, CA (US);
Canon Kabushiki Kaisha, , JP;
Abstract
An image scaling system that enlarges images during JPEG encoding (400) and reduces images during JPEG decoding (500). The image scaling system uses N-point forward and inverse one-dimensionial scaled discrete cosine transforms (DCTs), where N is selected from among 1, 2, 3, 4, and 6. When encoding a source image (110) to an enlarged JPEG image (422), the system partitions the source image into N.times.N blocks. Each N.times.N block is transformed using the N-point scaled DCT (410). The system modifies quantization tables (418) to account for the scale of the transform and the increase in size of the image and quantizes (412) the blocks of N.times.N scaled cosine coefficients using the modified quantization tables. The resulting N.times.N blocks are enlarged (414) to 8.times.8 blocks by padding each block with coefficients having values of zero. When decoding a JPEG image (510) to a reduced output image (518), the system retrieves 8.times.8 blocks of quantized cosine coefficients from the JPEG image. The system reduces (512) each block to an N.times.N block of quantized cosine coefficients. The system modifies the quantization tables (520) retrieved from the JPEG image to account for the scale factor and the decrease in size of the image, then quantizes (514) the N.times.N blocks to produce N.times.N blocks of scaled cosine coefficients. The system performs an N-point scaled inverse DCT (516) on each block of scaled cosine coefficients. The results of the inverse DCT form the reduced output image (518). The forward and inverse DCTs are performed using efficient processes that require relatively few calculations to achieve the desired result.