HSI MODEL IN COLOR IMAGE PROCESSING

HSI MODEL IN COLOR IMAGE PROCESSING

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  HSI COLOR MODEL -ANAMSINGLA
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  BASIC CONCEPT OFLIGHT SOURCE • The characteristics generally used to distinguish one color from another are brightness, hue, and saturation. • Hue is an attribute associated with the dominant wavelength in a mixture of light waves. • Hue represent dominant color as perceived by an observer. • Saturation refers to the relatives purity or the amount of white light mixed with a hue. The pure spectrum color are fully saturation.
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  WHY WE HAVENEED OF HSI MODEL? • RGB AND CMY model are suitable for hardware implementation. • These model are easily perceptive to human eye. • But they are suitable for describing color in terms that are practical for human interpretation. • Example- one doesn’t refer to the color of an object by giving the percentage of each of the primaries composing its color. • We describe it by hue, saturation and its brightness
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  Basic of HSIMODEL • The HSI (hue, saturation, intensity) color model, decouples the intensity component from the color-carrying information(hue and saturation) in a color image. • The HSI model is an ideal tool for developing image processing algorithms based on color descriptions that are natural and intuitive to humans.
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  The HSI modeluses three measures to describe colors: • Hue: A color attribute that describes a pure color (pure yellow, orange or red) • Saturation: Gives a measure of how much a pure color is diluted with white light • Intensity: Brightness is nearly impossible to measure because it is so subjective. Instead we use intensity. Intensity is the same achromatic notion that we have seen in grey level images
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  Relationship between theRGB and HSI color models • Now the intensity component of any color can be determined by passing a plane perpendicular to the intensity axis and containing the color point • The intersection of the plane with the intensity axis gives .us the intensity component of the color.
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  • In asimilar way we can extract the hue from the RGB color cube • Consider a plane defined by the three points cyan, black and white • All points contained in this plane must have the same hue (cyan) as black and white cannot contribute hue information to a color
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  Hue and Saturationin the HSI color model • Consider if we look straight down at the RGB cube as it was arranged previously • We would see a hexagonal shape with each primary color separated by 120° and secondary colors at 60° from the primaries • So the HSI model is composed of a vertical intensity axis and the locus of color points that lie on planes perpendicular to that axis
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  • To theright we see a hexagonal shape and an arbitrary color point • The hue is determined by an angle from a reference point, usually red • The saturation is the distance from the origin to the point • The intensity is determined by how far up the vertical intensity axis this hexagonal plane sits (not apparent from this diagram.
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  • The onlyimportant things are the angle and the length of the saturation vector this plane is also often represented as a circle or a triangle • The angle from the red axis gives the hue, and the length of the vector is the saturation. • The intensity of all colors in any of these planes is given by the position of the plane on the vertical intensity axis.
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  HSI Model Example
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  Converting from RGBto HSI • Given a color as R, G, and B its H, S, and I values are calculated as follows:
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  Converting from HSIto RGB • Given a color as H, S, and I it’s R, G, and B values are calculated as follows: • RG sector (0 <= H < 120°)
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  HSI & RGB •H, S, and I Components of RGB Color Cube.
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  Manipulating Images InThe HSI Model • In order to manipulate an image under the HIS model we: • First convert it from RGB to HSI • Perform our manipulations under HSI • Finally convert the image back from HSI to RGB
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  THANKYOU…. ۩