Patent ID: 7599564
Filing Date: 2009-10-06
Classification: H04N

Abstract:
1. A JPEG-compression-file generation method for generating a JPEG compression file from image data, using a second quantization table obtained based on a quantization data coefficient value and on a first quantization table as a reference, the method comprising: (a) a step of deriving using a computer, from the image data before JPEG compression, image feature value; (b) a step of deriving using a computer the quantization data coefficient value by, with respect to a relational expression, which includes the quantization data coefficient value and the image feature value, for expressing the file size of a JPEG compression file, designating a desired file size as the file size of the JPEG compression file, and the step (a) comprises: (a-1) a step of dividing the image data into a plurality of unit blocks; (a-2) a step of calculating for each of the unit blocks a pixel-value difference between pixels in predetermined positions; and (a-3) a step of deriving the image feature value by summing each pixel-value difference calculated in the step (a-2); and the step (a-2) comprises: (a-2-1) a step of deriving a first of the image feature values using a pixel-value difference between two pixels at a first distance range; and (a-2-2) a step of deriving a second of the image feature values using a pixel-value difference between two pixels at a second distance range.