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Chapter 6 Color Image Processing

Chapter 6 Color Image Processing. Color fundamentals. 六個區域 : 紫 , 藍 , 綠 , 黃 , 橙 , 紅 每個顏色都是平順的融入下一種顏色中. Chapter 6 Color Image Processing. 彩色光頻譜範圍 400~700nm. 描述彩色光源品質的三種基本量 輻射度 (Radiance) The total amount of energy that flows from the light source Measured in watts (W)

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Chapter 6 Color Image Processing

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  1. Chapter 6 Color Image Processing Color fundamentals 六個區域: 紫, 藍, 綠, 黃, 橙, 紅 每個顏色都是平順的融入下一種顏色中

  2. Chapter 6 Color Image Processing 彩色光頻譜範圍 400~700nm • 描述彩色光源品質的三種基本量 • 輻射度(Radiance) • The total amount of energy that flows from the light source • Measured in watts (W) • 照度(Luminance) • The energy an observer perceives from a light source. • Measured in lumens (lm) • 亮度(Brightness) • A subjective descriptor.

  3. Chapter 6 Color Image Processing • 錐狀細胞(Cones) 對於色彩感受度可以分為三類 • 65% -- red • 33% -- green • 2% -- blue (but the blue cones are the most sensitive) 三 “原(primary)” 色 (RGB)不代表它們可以組成頻譜上各種任意的顏色，除非波長可改變 CIE designated Red: 700 nm Green : 546.1 nm Blue: 435.8 nm

  4. Chapter 6 Color Image Processing • 加成性的原色(光的三原色) • 紅、藍、綠 • 可見的顏色是由物體直接發出 • 例:綠色—物體發出綠光 • 相減性的原色(顏料的三原色) • 紫紅、青、黃 • 物體吸收一種光的原色而反射另外的兩種光. • 例:黃色—物體吸收藍光，反射紅及綠光

  5. 用來區分彩色的特徵 亮度 Brightness 色彩強度 色調 Hue 與混合光波的主要波長有關, 代表觀察者所查覺得主要色彩 飽和度 Saturation 色彩的相度純度或與白光混合的量 Chromaticity(色度) – 包含 Hue 及 Saturation Chapter 6 Color Image Processing

  6. Chapter 6 Color Image Processing • CIE色度圖 • 橫軸:紅 • 縱軸:綠 • Z: 1-(x+y) 藍 • 所有頻譜色彩圍繞在舌形邊界(純色) • 等能量點:三原色等比例 • 連接任一兩點的直線定義兩端點顏色可以組合的所有顏色 • 由等能量點連至邊線可以定義該色頻顏色的深淺

  7. Chapter 6 Color Image Processing 色彩全域 Color gamut Color monitor Color printing device

  8. Chapter 6 Color Image Processing • 色彩模型(Color model, color space, color system) • Cartesian coordinate system • Color is defined by vector • Normalized value in the range [0,1] RGB色彩模型

  9. Chapter 6 Color Image Processing

  10. Chapter 6 Color Image Processing B Plane with R=128 G R

  11. Chapter 6 Color Image Processing • 安全色彩 • 系統 • 網路 • 瀏覽器 FFFFFF FFFFCC CCFFFF FFCCFF FF0000 40 顏色保留給系統進行處理與使用，其他(216色)共通，即所謂的安全色彩，其顯示與硬體無關

  12. Chapter 6 Color Image Processing • RGB均只有六個值 • 0,51,102,153,204,255 • 下圖將6.10圖以立體顯示

  13. Chapter 6 Color Image Processing • CMY 及 CMYK 色彩模型 • 青Cyan, 紫紅magenta, 及黃 yellow 是光的次色彩 • 下列公式中所有的顏色值均被正規化至 [0,1]之間 • K 為純黑色: 避免使用 C,M,Y 混出髒的黑色 塗有青色(C)的原料被白光照射時，紅光(R)被吸收 (C=1-R)

  14. Chapter 6 Color Image Processing • HSI 色彩模型 • Hue, Saturation, and Intensity RGB model – color generation( camera, monitor…) CMY model – color printing HSI model – color description, 根據人類直覺的彩色描述 發展影像處理的工具

  15. Chapter 6 Color Image Processing

  16. Chapter 6 Color Image Processing

  17. Chapter 6 Color Image Processing • Converting colors from RGB to HSI (R,G,B are normalized )

  18. Chapter 6 Color Image Processing • Converting colors from HSI to RGB 請注意譯本的公式有誤

  19. Chapter 6 Color Image Processing

  20. Chapter 6 Color Image Processing 請注意譯本的圖片有誤

  21. Chapter 6 Color Image Processing

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