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數位影像處理概述

數位影像處理概述. 長庚電機通訊組 碩一 張晉銓 指導教授 : 黃文傑博士. Table of contents. Basic digital image structure Discrete cosine transform DCT use in JPEG Pictures about FT and DCT Review Watermarking of Cox. 數位影像基本認識. 影像單位： pixel ( 畫素 ) 層階影像例子： ２值影像： f (x,y)=0 or 1

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數位影像處理概述

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  1. 數位影像處理概述 長庚電機通訊組 碩一 張晉銓 指導教授:黃文傑博士

  2. Table of contents • Basic digital image structure • Discrete cosine transform • DCT use in JPEG • Pictures about FT and DCT • Review Watermarking of Cox

  3. 數位影像基本認識 • 影像單位：pixel(畫素) • 層階影像例子： ２值影像：f (x,y)=0 or 1 層階影像： f (x,y)以數段階明亮來表示的影像 　　　　　　階層有2,4,8,256… 彩色影像：f (x,y)有RGB等3原色來表示,若各 　　　　　　色皆為256階,大多稱為全彩 資料量512*512*(8*3)=786.432KByte

  4. 影像處理的轉換法所需的特性 • 影像內像素間的相關性要打散 • 與影像無關的基底函數 • 快速完成轉換

  5. Discrete cosine transform ,DCT 下列為DFT有限序列轉換表示的一般式 其中Φ(k)被稱為基底序列(basis sequence) DCT的型式與上式相同，Φ(k)(basis sequence)為餘弦，所以DCT具有週期性與偶對稱的特點

  6. Discrete cosine transform ,DCT 一個序列組成一個對稱且週期性的擴展有4種方法

  7. Discrete cosine transform ,DCT

  8. Discrete cosine transform ,DCT

  9. Discrete cosine transform ,DCT • JPEG使用二維的DCT-II，處理8*8的矩陣資料轉換成64個係數(1個DC與63個AC)

  10. Discrete cosine transform ,DCT

  11. JPEG Baseline system (8*8)

  12. JPEG Baseline system (8*8)

  13. 改良後Cox法 • vi’= vi +αxi

  14. 結束 謝 謝 大 家 !!!

  15. FT示意圖

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