US 5,850,484: Text and image sharpening of JPEG compressed images in the frequency domain

Inventor(s):	Beretta; Giordano , Palo Alto, CA Bhaskaran; Vasudev , Mountain View, CA Konstantinides; Konstantinos , San Jose, CA
Applicant(s):	Hewlett-Packard Company, Palo Alto, CA
Issued/Filed Dates:	Dec. 15, 1998 / Sept. 30, 1997
Application Number:	US1997000940695
IPC Class:	G06K 009/36;
Class:	382/250; 382/251; 382/239; 358/432; 348/404
Field of Search:	382/298, 233, 251, 244, 232, 253, 250, 274, 252, 238, 236, 166, 2 80, 270, 358/427, 426, 432, 261.3, 448, 261.1, 433, 261.2, 430, 458, 348/404, 432,4 05, 433, 403, 391, 384, 422, 393, 430, 394, 409, 395, 390
Abstract:	The text and image enhancing technique according to the invention is integrated into the decoding or inverse quantization step that is necessarily required by the JPEG standard. The invention integrates the two by using two different quantization tables: a first quantization table (QE) for use in quantizing the image data during the compression step and a second quantization table used during the decode or inverse quantization during the decompression process. The second quantization table QD is related to the first quantization table according to a predetermined function of the energy in a reference image and the energy in a scanned image. The energy of the reference image lost during the scanning process, as represented by the energy in the scanned image, is restored during the decompression process by appropriately scaling the second quantization table according to the predetermined function. The difference between the two tables, in particular the ratio of the two tables, determines the amount of image enhancing that is done in the two steps. By integrating the image enhancing and inverse quantization steps the method does not require any additional computations than already required for the compression and decompression processes.
Primary/Assistant Examiners:	Couso; Jose L.; Bella; Matthew C.
Related Applications:	Application Number Appl Date Patent Issued Title US1995000411369 1995-03-27
U.S. References:	(No patents reference this one) Patent Inventor(s) Issued Title US4776030 Tzou 10 /1988 Block quantizer for transform coding US4780761 Daly et al. 10 /1988 Digital image compression and transmission US5063608 Siegel 11 /1991 Adaptive zonal coder US5073820 Nakagawa et al. 12 /1991 Image data coding apparatus and coding method US5333212 Ligtenberg 7 /1994 Image compression technique with regionally US5410352 Watanabe 4 /1995 Image data compressing apparatus US5465164 Sugiura 11 /1995 Image processing method and device for the US5488570 Agarwal 1 /1996 Encoding and decoding video signals using
First Claim:	We claim: A machine for transmitting color images comprising: means for rendering a color image into color source image data representing the color image; a compression engine that compresses the source image data into compressed image data, the engine including: a transforming means for converting the source image data into transformed image data, means for storing a first multi-element quantization table (QE); a quantizer means for converting the transformed image data into quantized image data in accordance with elements contained in the first quantization table, means for storing a second multi-element quantization table (QD) related to but nonidentical to the first quantization table QE, an entropy encoder means for transforming the quantized image data into the encoded image data using an entropy table; means for encapsulating the encoded image data, the second quantization table, and the entropy table to form an encapsulated data file; and means for transmitting the encapsulated data file. CROSS REFERENCE TO RELATED APPLICATIONS This is a continuation of application Ser. No. 08/411,369 filed on Mar. 27, 1995, now abandoned.
Foreign References:	Publication  Country Date IPC Class EP19910444884A2 European Patent Office (EPO) 2 /1991   EP19920513520A2 European Patent Office (EPO) 4 /1992 H04N007133 EP19930593159A2 European Patent Office (EPO) 9 /1993 G06F01564 JP1995000087491 Japan 3 /1995 H04N00730 JP1995000143343 Japan 6 /1995 H04N00141
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