# Color Reflection

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3.4.1 Color feature extraction Color moments are the measures that describe the color distribution of an image and the central moments are used to describe a probability distribution. Main purpose of color moment is to form the color indexing for image retrieval applications. The color moments are invariant for scaling and rotation. Here, the first three order moments are used as features for image retrieval. Three color moments are calculated for each channel. For example, 9 color moments are calculated for RGB and 12 color moments for CMYK. The color moments encode both shape and color information. It can be computed for each channel in any color model. Color model is a mathematical representation of color. Here, the color is represented…show more content…
Angular second moment (ASM) feature This feature is used to measure the uniformity or energy from an image. Angular Second Moment is very large, if the pixels are very similar. (3.9) 2. Contrast Feature Generally, contrast is defined as a difference between the color and the brightness of an object. Contrast is a measure of intensity or gray level variations between current pixels and its neighbor. (3.10) If the value of i and j are equal, then the cell is on the diagonal. These values indicate that the pixels entirely similar to their neighbor. Here the weight n is also 0. If the difference between i and j is 1, then there is a small contrast between the pixels and the weight is 1. If i and j are differed by 2, then the pixels have more contrast with its neighboring pixels. Here the weight value is 4. The weight and the value of i-j are directly proportional to each other. The value of i-j increases with the weight. 3. Entropy Feature Entropy is a term used in thermodynamics to measure the proximity among the systems or it is used to define the disorder between systems. Higher entropy means greater disorder values. The following equation is used to define entropy: (3.11) 4. Variance