第六章 彩色图像处理_2012.pdf

彩色图像处理 Two principal motivating factors for using color in image processing: 1. Color is a powerful descriptor that often simplifies object identification and extraction from a scene. 2. Humans can discern thousands of color shades and intensities, but just only two dozen of shades of grays. Color image processing includes three major areas: 1. Full-color: the images in question typically are acquired with a full-color sensor, such as a color TV camera or scanner. 2. false-color: processing intentionally the natural color images or multi-spectral sensor images into false color images. 3. pesudo-color processing: assigning a color to a particular monochrome intensity or range of intensities. 6.1 color fundamentals Six bands in color spectrum: Violet, blue, green, yellow, orange and red, each colors blends smoothly into next. The colors of object are often determined by the nature of the light reflected from the object, for example, green objects reflect light with wavelengths primarily in the 500 to 700 nm range. The electromagnetic spectrum of chromatic light ranges from about 400 to 700nm, three basic features used to describe the quality of a chromatic light: radiance, luminance, and brightness. Radiance: the amount of energy that flows from the light source, measured in watts (W); Luminance: a measure of the amount of energy an observer perceives from a light source, measured in lumens (lm); Brightness: a subjective descriptor practically impossible to measure. Three primary colors designated by visual characteristics Red (R), green (G) and blue (B), the wavelength specified by CIE is 700nm, 546.1nm and 435.8nm respectively. Absorption experiment of color light of cones in human eye: 光 的 蓝 绿 红 吸 收 率 400 450 500 550 600 650 700nm