https://mediawiki.zeropage.org/index.php?action=history&feed=atom&title=PNGFileFormat%2FFilterAlgorithms 2026-05-15T00:28:53Z Revision history for this page on the wiki MediaWiki 1.39.8 https://mediawiki.zeropage.org/index.php?title=PNGFileFormat/FilterAlgorithms&diff=37431&oldid=prev 2021-02-07T05:23:59Z

<p></p> <p><b>New page</b></p><div>=== 범례 ===<br /> * bpp : bytes per pixel<br /> * Raw(x) : 실제 픽셀값<br /> * Sub(x) : zlib 으로 decompress한 바이트배열의 값<br /> * Prior(x) : 위쪽 스캔라인의 대응위치의 실제 변환된 RGB 값. x&lt;0이면 0.<br /> * Prior(x-bpp) : 위쪽 스캔라인의 대응위치 왼쪽의 실제 변환된 RGB 값. x&lt;0이면 0.<br /> <br /> === Filter type 0 : None ===<br /> * 그냥 생짜 정보.<br /> <br /> === Filter type 1 : Sub ===<br /> Sub(x) = Raw(x) - Raw(x-bpp) 즉, Raw(x) = Sub(x) + Raw(x-bpp)<br /> <br /> <br /> === Filter type 2 : Up ===<br /> === Filter type 3 : Average ===<br /> === Filter type 4 : Paeth ===<br /> Raw(x) = Paeth(x) + PaethPredictor(Raw(x-bpp), Prior(x), Prior(x-bpp))<br /> <br /> function PaethPredictor (a,b,c)<br /> begin<br /> ; a = left, b = above; c = upper left<br /> p = a + b - c<br /> pa = abs(p-a)<br /> pb = abs(p-b)<br /> pc = abs(p-c)<br /> if pa &amp;lt;= pb and pa &amp;lt;= pc then a<br /> else if pb &amp;lt;= pc then b<br /> else c<br /> <br /> <br /> ----<br /> [[PNGFileFormat]]<br /> </div>

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