09_COLOUR.ppt

Color Why study Color ? Synthesis of realistic images has been the primary goal of computer graphics In this quest for realism it is necessary to relate the perceptual processing of visual information to the image display technology Understanding color perception and its relationship to both color computation and color reproduction becomes important What is color ? Color is the brain’s reaction to a specific visual stimulus Subjective sensation experienced by the observer. There is no such thing called color without an observer Depends upon Physics of light Interaction of light with physical materials Interpretation of the resulting phenomenon by the human visual system and the human brain Physics of Light Light is a dynamic phenomenon which is difficult to observe Research is still on in trying to model the behavior of light Currently there are two models proposed by physicists to explain the behavior of light Wave Model, which treats light as water waves Particle Model, which assumes that light is made of tiny , invisible, vibrating particles called photons From color point of view the particle model is used Properties of Light The photons as they move along a straight line vibrate with a particular frequency Photons are assumed to carry certain amount of energy proportional to their frequency of vibration (frequency increases energy increases) , given by where, h is the Planck’s constant and f is the frequency of vibration Photon behavior is cyclic and has a repeated pattern Properties of Light Distance traveled by the photon from the beginning of one cycle to the beginning of next is known as the wavelength, given by where, c is the speed of light and f is the frequency Each photon has a wavelength associated with it and the perceived color of light depends on this wavelength The intensity of light depends on the number of photons present Spectrum(光谱) of Electromagnetic Radiation Light is a continuou