L12_compresie-imag-DCT.rar

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L12_compresie_imagDCT conteins image compression algorithms using DCT
L12_compresie-imag-DCT.rar
  • L12_compresie imag DCT
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内容介绍
<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta charset="utf-8"> <meta name="generator" content="pdf2htmlEX"> <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> <link rel="stylesheet" href="https://static.pudn.com/base/css/base.min.css"> <link rel="stylesheet" href="https://static.pudn.com/base/css/fancy.min.css"> <link rel="stylesheet" href="https://static.pudn.com/prod/directory_preview_static/637fc4ce9f0e6d0d65350773/raw.css"> <script src="https://static.pudn.com/base/js/compatibility.min.js"></script> <script src="https://static.pudn.com/base/js/pdf2htmlEX.min.js"></script> <script> try{ pdf2htmlEX.defaultViewer = new pdf2htmlEX.Viewer({}); }catch(e){} </script> <title></title> </head> <body> <div id="sidebar" style="display: none"> <div id="outline"> </div> </div> <div id="pf1" class="pf w0 h0" data-page-no="1"><div class="pc pc1 w0 h0"><img class="bi x0 y0 w1 h1" alt="" src="https://static.pudn.com/prod/directory_preview_static/637fc4ce9f0e6d0d65350773/bg1.jpg"><div class="c x0 y1 w2 h2"><div class="t m0 x1 h3 y2 ff1 fs0 fc0 sc0 ls0 ws0">L7- Compresia imaginilor prin utilizarea transformarilor </div><div class="t m0 x2 h3 y3 ff2 fs0 fc0 sc0 ls0 ws0">(<span class="ff3">Transform-Domain Coding</span>)</div><div class="t m0 x3 h3 y4 ff1 fs0 fc0 sc0 ls0 ws0">1. Introducere</div><div class="t m0 x4 h3 y5 ff2 fs0 fc0 sc0 ls0 ws0">Metodele de compresie prin utilizarea codarii transformarii sunt din categoria<span class="_ _0"></span> de compresia cu pierdere de</div><div class="t m0 x4 h3 y6 ff2 fs0 fc0 sc0 ls0 ws0">informatie, avand structura de baza prezentata in figura 1.</div><div class="t m0 x5 h3 y7 ff2 fs0 fc0 sc0 ls0 ws0">Figura 1 &#8211; Transformari de baza in compresia prin codarea transformarii</div><div class="t m0 x4 h3 y8 ff2 fs0 fc0 sc0 ls0 ws0">Primul bloc realizeaza<span class="_ _0"></span> reducerea<span class="_ _0"></span> gamei dinamice<span class="_ _0"></span> a semnalului<span class="_ _0"></span> (imagine) <span class="_ _0"></span>in vederea<span class="_ _0"></span> eliminarii <span class="_ _0"></span>informatiei</div><div class="t m0 x4 h3 y9 ff2 fs0 fc0 sc0 ls0 ws0">redundante<span class="_ _1"> </span> <span class="_ _1"> </span>si<span class="_ _1"> </span> <span class="_ _1"> </span>realizeaza<span class="_ _2"> </span> <span class="_ _1"> </span>impartirea<span class="_ _1"> </span> <span class="_ _1"> </span>imaginii<span class="_ _2"> </span> <span class="_ _1"> </span>in<span class="_ _1"> </span> <span class="_ _1"> </span>sub-blocuri<span class="_ _1"> </span> <span class="_ _2"> </span>acceptabile<span class="_ _1"> </span> <span class="_ _1"> </span>pentru<span class="_ _1"> </span> <span class="_ _1"> </span>realizarea<span class="_ _2"> </span> <span class="_ _1"> </span>eficienta<span class="_ _1"> </span> <span class="_ _1"> </span>a</div><div class="t m0 x4 h3 ya ff2 fs0 fc0 sc0 ls0 ws0">operatiei<span class="_ _3"></span> <span class="_ _3"></span>urmatoare,<span class="_ _3"></span> <span class="_ _3"></span>o<span class="_ _3"></span> <span class="_ _4"></span>transformare.<span class="_ _3"></span> <span class="_ _3"></span>Transformarea<span class="_ _4"></span> <span class="_ _3"> </span>s<span class="_ _0"></span>e<span class="_ _4"></span> <span class="_ _3"></span>aplica<span class="_ _3"></span> <span class="_ _3"></span>pentru<span class="_ _3"></span> <span class="_ _4"></span>obtinerea<span class="_ _1"> </span> <span class="_ _4"></span>unei<span class="_ _3"></span> <span class="_ _4"></span>reprezentar<span class="_ _0"></span>i<span class="_ _3"></span> <span class="_ _3"></span>ce<span class="_ _4"></span> <span class="_ _3"></span>se</div><div class="t m0 x4 h3 yb ff2 fs0 fc0 sc0 ls0 ws0">poate<span class="_ _3"></span> <span class="_ _4"></span>coda<span class="_ _3"></span> <span class="_ _3"></span>mai<span class="_ _3"></span> <span class="_ _4"></span>eficient.<span class="_ _3"></span> <span class="_ _3"></span>Blocul<span class="_ _3"></span> <span class="_ _3"></span>de<span class="_ _4"></span> <span class="_ _3"></span>cuantizare<span class="_ _3"></span> <span class="_ _3"></span>exista<span class="_ _3"></span> <span class="_ _4"></span>numai<span class="_ _3"></span> <span class="_ _3"></span>in<span class="_ _3"></span> <span class="_ _4"></span>metodele<span class="_ _3"></span> <span class="_ _3"></span>de<span class="_ _3"></span> <span class="_ _4"></span>compresie<span class="_ _3"></span> <span class="_ _3"></span>cu<span class="_ _3"></span> <span class="_ _4"></span>pierdere<span class="_ _3"></span> <span class="_ _3"></span>de</div><div class="t m0 x4 h3 yc ff2 fs0 fc0 sc0 ls0 ws0">informatie, intruct prin<span class="_ _0"></span> cuantizare numarul<span class="_ _0"></span> de simboluri ce<span class="_ _0"></span> trebuie codat <span class="_ _0"></span>se reduce. Ultimul <span class="_ _0"></span>bloc, codarea</div><div class="t m0 x4 h3 yd ff2 fs0 fc0 sc0 ls0 ws0">entropica,<span class="_ _3"> </span> <span class="_ _1"> </span>presupune<span class="_ _3"></span> <span class="_ _1"> </span>folosirea<span class="_ _3"></span> <span class="_ _1"> </span>unor<span class="_ _3"></span> <span class="_ _1"> </span>tehni<span class="_ _5"></span>ci<span class="_ _1"> </span> <span class="_ _3"></span>de<span class="_ _3"> </span> <span class="_ _1"> </span>codare<span class="_ _3"></span> <span class="_ _1"> </span>tip<span class="_ _3"></span> <span class="_ _1"> </span>Huffman<span class="_ _3"></span> <span class="_ _1"> </span>sau<span class="_ _3"></span> <span class="_ _1"> </span>codare<span class="_ _3"></span> <span class="_ _1"> </span>arit<span class="_ _5"></span>metica<span class="_ _1"> </span> <span class="_ _3"></span>in<span class="_ _1"> </span> <span class="_ _3"></span>vederea</div><div class="t m0 x4 h3 ye ff2 fs0 fc0 sc0 ls0 ws0">obtinerii unei eficiente aproape de entropiei sursei ce are ca simboluri coeficientii<span class="_ _0"></span> cuantizati. </div><div class="t m0 x4 h3 yf ff2 fs0 fc0 sc0 ls0 ws0">In<span class="_ _6"> </span> <span class="_ _6"> </span>general,<span class="_ _6"> </span> <span class="_ _7"> </span>imaginea<span class="_ _6"> </span> <span class="_ _6"> </span>de<span class="_ _6"> </span> <span class="_"> </span>int<span class="_ _5"></span>rare<span class="_ _6"> </span> <span class="_ _6"> </span>este<span class="_ _6"> </span> <span class="_"> </span>impart<span class="_ _5"></span>ita<span class="_ _6"> </span> <span class="_ _7"> </span>(divizata)<span class="_ _6"> </span> <span class="_ _6"> </span>in<span class="_ _6"> </span> <span class="_"> </span>bl<span class="_ _5"></span>ocuri<span class="_ _6"> </span> <span class="_ _6"> </span>disjuncte,<span class="_ _6"> </span> <span class="_"> </span>de<span class="_ _6"> </span> <span class="_ _6"> </span>marime<span class="_ _8"> </span> <span class="_ _0"></span><span class="ff3">NxN</span>.</div><div class="t m0 x4 h3 y10 ff2 fs0 fc0 sc0 ls0 ws0">Transformarea<span class="_ _4"></span> <span class="_ _4"></span>poate<span class="_ _4"></span> <span class="_ _4"></span>fi<span class="_ _4"></span> <span class="_ _4"></span>reprezentata<span class="_ _4"></span> <span class="_ _4"></span>ca<span class="_ _4"></span> <span class="_ _4"></span>o<span class="_ _4"></span> <span class="_ _4"></span>operatie<span class="_ _4"></span> <span class="_ _3"></span>matriciala<span class="_ _4"></span> <span class="_ _4"></span>utilizand<span class="_ _4"></span> <span class="_ _4"></span>o<span class="_ _4"></span> <span class="_ _4"></span>matrice<span class="_ _4"></span> <span class="_ _4"></span>de<span class="_ _4"></span> <span class="_ _4"></span>transformare<span class="_ _2"> </span> <span class="_ _0"></span><span class="ff1">A<span class="_ _0"></span></span>,<span class="_ _4"></span> <span class="_ _4"></span>in</div><div class="t m0 x4 h3 y11 ff2 fs0 fc0 sc0 ls0 ws0">vederea<span class="_ _9"></span> <span class="_ _0"></span>obtinerii<span class="_ _9"></span> <span class="_ _9"></span>celor<span class="_ _3"></span> <span class="ff3">NxN</span> <span class="_ _3"></span>coeficienti<span class="_ _0"></span> <span class="_ _9"></span>de<span class="_ _9"></span> <span class="_ _9"></span>transformare,<span class="_ _9"></span> <span class="_ _9"></span>folosind<span class="_ _9"></span> <span class="_ _0"></span>o<span class="_ _9"></span> <span class="_ _9"></span>transformare<span class="_ _9"></span> <span class="_ _9"></span>liniara,<span class="_ _9"></span> <span class="_ _0"></span>s<span class="_ _0"></span>eparabila<span class="_ _9"></span> <span class="_ _0"></span>s<span class="_ _0"></span>i<span class="_ _0"></span> <span class="_ _9"></span>de</div><div class="t m0 x4 h3 y12 ff2 fs0 fc0 sc0 ls0 ws0">norma unitara de tipul:</div><div class="t m0 x4 h3 y13 ff2 fs0 fc0 sc0 ls0 ws0">Transformarea<span class="_ _1"> </span> <span class="_ _2"> </span>este<span class="_ _a"> </span> <span class="ff3">reversibila</span> <span class="_ _a"> </span>pentru<span class="_ _1"> </span> <span class="_ _2"> </span>ca<span class="_ _1"> </span> <span class="_ _2"> </span>blocul<span class="_ _2"> </span> <span class="_ _1"> </span>de<span class="_ _2"> </span> <span class="_ _1"> </span>pixeli<span class="_ _2"> </span> <span class="_ _1"> </span>original,<span class="_ _2"> </span> <span class="_ _1"> </span>poate<span class="_ _2"> </span> <span class="_ _1"> </span>fi<span class="_ _2"> </span> <span class="_ _2"> </span>reconstruit<span class="_ _1"> </span> <span class="_ _2"> </span>utilizand<span class="_ _1"> </span> <span class="_ _2"> </span>o</div><div class="t m0 x4 h3 y14 ff2 fs0 fc0 sc0 ls0 ws0">transformare<span class="_ _9"></span> <span class="_ _9"></span>inversa<span class="_ _9"></span> <span class="_ _9"></span>unitara,<span class="_ _4"></span> <span class="_ _9"></span>unde<span class="_ _9"></span> <span class="_ _9"></span>inversa<span class="_ _9"></span> <span class="_ _4"></span>matricii<span class="_ _9"></span> <span class="_ _9"></span>A<span class="_ _9"></span> <span class="_ _9"></span>este<span class="_ _4"></span> <span class="_ _9"></span>identica<span class="_ _9"></span> <span class="_ _9"></span>cu<span class="_ _4"></span> <span class="_ _0"></span>matricea<span class="_ _4"></span> <span class="_ _9"></span>transpusa,<span class="_ _9"></span> <span class="_ _9"></span>deci<span class="_ _3"> </span> <span class="_ _9"></span><span class="ff1">A</span></div><div class="t m0 x6 h4 y15 ff1 fs1 fc0 sc0 ls0 ws0">-1</div><div class="t m0 x7 h3 y14 ff1 fs0 fc0 sc0 ls0 ws0"> <span class="_ _3"></span>=A</div><div class="t m0 x8 h4 y15 ff1 fs1 fc0 sc0 ls0 ws0">T</div><div class="t m0 x9 h3 y14 ff2 fs0 fc0 sc0 ls0 ws0">,</div><div class="t m0 x4 h3 y16 ff2 fs0 fc0 sc0 ls0 ws0">astfel incat</div><div class="t m0 x4 h3 y17 ff2 fs0 fc0 sc0 ls0 ws0">Transformarea insasi nu face nici <span class="_ _0"></span>o compresie. Scopul transformarii este<span class="_ _0"></span> de a decorela s<span class="_ _0"></span>emnalul de intrare</div><div class="t m0 x4 h3 y18 ff2 fs0 fc0 sc0 ls0 ws0">ceea<span class="_ _2"> </span> <span class="_ _1"> </span>ce<span class="_ _2"> </span> <span class="_ _2"> </span>duce<span class="_ _2"> </span> <span class="_ _2"> </span>la<span class="_ _2"> </span> <span class="_ _2"> </span>re-distributia<span class="_ _2"> </span> <span class="_ _2"> </span>energiei<span class="_ _2"> </span> <span class="_ _2"> </span>semnalului<span class="_ _2"> </span> <span class="_ _2"> </span>peste<span class="_ _2"> </span> <span class="_ _2"> </span>un<span class="_ _1"> </span> <span class="_ _2"> </span>numar<span class="_ _2"> </span> <span class="_ _2"> </span>mic<span class="_ _2"> </span> <span class="_ _2"> </span>de<span class="_ _2"> </span> <span class="_ _2"> </span>coeficienti,<span class="_ _2"> </span> <span class="_ _2"> </span>coeficientii</div><div class="t m0 x4 h3 y19 ff2 fs0 fc0 sc0 ls0 ws0">transformarii.<span class="_ _3"></span> <span class="_ _3"></span>Intrucat<span class="_ _1"> </span> <span class="_ _4"></span>energia<span class="_ _1"> </span> <span class="_ _3"></span>semnalului<span class="_ _3"></span> <span class="_ _3"></span>se<span class="_ _3"></span> <span class="_ _3"> </span>conserva<span class="_ _1"> </span> <span class="_ _4"></span>rezulta<span class="_ _1"> </span> <span class="_ _3"></span>ca<span class="_ _3"></span> <span class="_ _3"></span>u<span class="_ _3"></span> <span class="_ _3"></span>are<span class="_ _1"> </span> <span class="_ _3"></span>loc<span class="_ _3"></span> <span class="_ _3"></span>pierdere<span class="_ _3"></span> <span class="_ _3"></span>de<span class="_ _1"> </span> <span class="_ _3"></span>energie<span class="_ _3"></span> <span class="_ _3"></span>si<span class="_ _3"></span> <span class="_ _3"> </span>de</div><div class="t m0 x4 h3 y1a ff2 fs0 fc0 sc0 ls0 ws0">informatie.<span class="_ _9"></span> <span class="_ _0"></span>In<span class="_ _9"></span> <span class="_ _9"></span>acest<span class="_ _9"></span> <span class="_ _9"></span>fel<span class="_ _9"></span> <span class="_ _9"></span>multi<span class="_ _9"></span> <span class="_ _9"></span>coeficienti<span class="_ _9"></span> <span class="_ _9"></span>pot<span class="_ _9"></span> <span class="_ _9"></span>fi<span class="_ _9"></span> <span class="_ _9"></span>neglijati<span class="_ _9"></span> <span class="_ _9"></span>dupa<span class="_ _9"></span> <span class="_ _9"></span>cuantizare<span class="_ _9"></span> <span class="_ _9"></span>si<span class="_ _9"></span> <span class="_ _9"></span>inaintea<span class="_ _0"></span> <span class="_ _4"></span>codarii.<span class="_ _0"></span> <span class="_ _9"></span>In<span class="_ _9"></span> <span class="_ _9"></span>plus,<span class="_ _9"></span> <span class="_ _9"></span>prin</div><div class="t m0 x4 h3 y1b ff2 fs0 fc0 sc0 ls0 ws0">considerarea<span class="_ _0"></span> s<span class="_ _0"></span>i <span class="_ _0"></span>includerea<span class="_ _0"></span> <span class="_ _0"></span>unui<span class="_ _0"></span> <span class="_ _0"></span>model <span class="_ _0"></span>al<span class="_ _0"></span> <span class="_ _0"></span>aparatului<span class="_ _0"></span> <span class="_ _0"></span>vizual,<span class="_ _0"></span> <span class="_ _0"></span>in<span class="_ _0"></span> <span class="_ _0"></span>speta<span class="_ _0"></span> a<span class="_ _0"></span> <span class="_ _0"></span>functiei<span class="_ _0"></span> <span class="_ _0"></span>de<span class="_ _0"></span> s<span class="_ _0"></span>ensibilitate<span class="_ _0"></span> la<span class="_ _0"></span> <span class="_ _0"></span>constrast,</div><div class="t m0 x4 h3 y1c ff2 fs0 fc0 sc0 ls0 ws0">in procesul de cuantizare a coeficientilor rezulta &#8211; de asemenea<span class="_ _0"></span> &#8211; o marire a eficientei compresiei.</div><div class="t m0 x4 h3 y1d ff2 fs0 fc0 sc0 ls0 ws0">Cele<span class="_ _0"></span> <span class="_ _0"></span>mai<span class="_ _9"></span> <span class="_ _0"></span>folosite<span class="_ _9"></span> <span class="_ _0"></span>transformari<span class="_ _9"></span> <span class="_ _0"></span>sunt:<span class="_ _9"></span> <span class="_ _0"></span>Transformata<span class="_ _0"></span> <span class="_ _9"></span>Fourier<span class="_ _0"></span> <span class="_ _9"></span>Discreta<span class="_ _0"></span> <span class="_ _0"></span>(D<span class="_ _0"></span>FT),<span class="_ _0"></span> <span class="_ _0"></span>Trasformata<span class="_ _9"></span> <span class="_ _0"></span>Karhunen-Loeve</div><div class="t m0 x4 h3 y1e ff2 fs0 fc0 sc0 ls0 ws0">(KLT), Transformata cosinus discreta (DCT), Trasformata Walsh-Hadamard (WHT). </div></div></div><div class="pi" data-data='{"ctm":[1.611850,0.000000,0.000000,1.611850,0.000000,0.000000]}'></div></div> </body> </html>
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