2-Image

2-Image - Human Vision, Color and Basic Image Processing...

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Unformatted text preview: Human Vision, Color and Basic Image Processing Jason Lawrence CS 4810: Graphics Acknowledgement: slides by Misha Kazhdan, Allison Klein, Tom Funkhouser, Adam Finkelstein and David Dobkin Outline Human Vision and Color Image Representation Reducing Color Quantization Artifacts Basic Image Processing Outline Human Vision and Color Image Representation Reducing Color Quantization Artifacts Basic Image Processing Human Vision Model of Human Visual System Human eye Objects in world Sun Human Vision Model of Human Visual System Human eye Objects in world Sun Vision Components: Incoming Light The Human Eye Typical Human Eye 5 Color Two types of receptors: 6 Rods and cones Cones in fovea Rods and Cones Rods More sensitive in low light: scotopic vision More dense near periphery Cones Only function with higher light levels: photopic vision Densely packed at center of eye: fovea Different types of cones color vision 7 Electromagnetic Spectrum Visible light frequencies range between ... o Red = 4.3 x 10 14 hertz (700nm) o Violet = 7.5 x 10 14 hertz (400nm) Figures 15.1 from H&B Visible Light The human eye can see light in the frequency range 400nm 700nm White Light Figure 15.3 from H&B Frequency Energy Red (700 nm) Violet (400 nm) Visible Light The human eye can see light in the frequency range 400nm 700nm White Light Figure 15.3 from H&B Frequency Energy Red (700 nm) Violet (400 nm) This does not mean that we can see the difference between the different spectral distributions. Visible Light Color may be characterized by Hue = dominant frequency (highest peak) Saturation = excitation purity (ratio of highest to rest) Lightness = luminance (area under curve) 11 White Light Orange Light Tristimulus Theory of Color Figure 13.18 from FvDFH Spectral-response functions of each of the three types of cones. This motivates encoding color as a combination of red, green, and blue (RGB). Tristimulus Color Any distribution of light can be summarized by its effect on 3 types of cones Therefore, human perception of color is a 3-dimensional space Metamerism: different spectra, same response Color blindness: fewer than 3 types of cones Most commonly L cone = M cone 13 Color Models RGB XYZ CMYK HSV etc......
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2-Image - Human Vision, Color and Basic Image Processing...

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