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Article #1247Re: DCTEncode filter
From: Gernot Hoffmann
Date: Sun, 02 Mar 2003 14:21
Date: Sun, 02 Mar 2003 14:21
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1483 bytes
Miklos, not so much conversation in this Forum .. Perhaps it�s therefore allowed to contribute though I didn�t test the JPEG conversion in PS (but programmed in Pascal). DCTEncode performs a complete JPEG conversion for all pixels, organized in 16x16 blocks. Subsampling, YCbCr conversion, DCT for 4 Y blocks and 1 Cb and 1 Cr block, each 8x8. Then the Quantization, the ZigZag scan, the Runlength coding for zeros and finally the Huffman coding. Result is a BIT-stream which cannot be compressed further. An ASCII85 conversion doesn�t make any sense IMO. If we consider the Huffman bitstream as a sequence of bytes, then an ASCII85 Encoding would pack 4 binary bytes into 5 ASCII bytes. The file would become even larger. Best regards --Gernot
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X-Google-Language: ENGLISH,ASCII X-Google-Thread: 10c61a,f51afc5ab2ff2b54 X-Google-Attributes: gid10c61a,public X-Google-ArrivalTime: 2003-03-02 06:37:29 PST From: "Gernot Hoffmann" <hoffmann@fho-emden.de> Path: arc1-ca.pugleaf.net!archiver1.google.com!news1.google.com!sn-xit-02!sn-xit-06!sn-xit-09!supernews.com!news.maxwell.syr.edu!skynet.be!skynet.be!fu-berlin.de!newsfeed01.sul.t-online.de!t-online.de!WebX Newsgroups: adobe.postscript.programming Subject: Re: DCTEncode filter Message-ID: <1de81742.0@WebX.la2eafNXanI> Date: Sun, 2 Mar 2003 06:21:13 -0800 References: <1de81742.-1@WebX.la2eafNXanI> Lines: 19 MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 8bit