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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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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

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.


Chapter 6 color image processing

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


Chapter 6 color image processing

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


Chapter 6 color image processing

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


Chapter 6 color image processing

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


Chapter 6 color image processing

Chapter 6

Color Image Processing

色彩全域

Color gamut

Color monitor

Color printing device


Chapter 6 color image processing

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


Chapter 6 color image processing

Chapter 6

Color Image Processing


Chapter 6 color image processing

Chapter 6

Color Image Processing

B

Plane with R=128

G

R


Chapter 6 color image processing

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


Chapter 6 color image processing

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


Chapter 6 color image processing

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)


Chapter 6 color image processing

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


Chapter 6 color image processing

Chapter 6

Color Image Processing


Chapter 6 color image processing

Chapter 6

Color Image Processing


Chapter 6 color image processing

Chapter 6

Color Image Processing

  • Converting colors from RGB to HSI

    (R,G,B are normalized )


Chapter 6 color image processing

Chapter 6

Color Image Processing

  • Converting colors from HSI to RGB

請注意譯本的公式有誤


Chapter 6 color image processing

Chapter 6

Color Image Processing


Chapter 6 color image processing

Chapter 6

Color Image Processing

請注意譯本的圖片有誤


Chapter 6 color image processing

Chapter 6

Color Image Processing


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