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Face Detection and Modeling for Recognition - Biometrics Research ...

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Appendix A<br />

Trans<strong>for</strong>mation of Color Space<br />

In this appendix, we will give the detailed <strong>for</strong>mulae of two types of colorspace trans<strong>for</strong>mations<br />

<strong>and</strong> an elliptical skins classifier, which are used in our face detection<br />

algorithm. The trans<strong>for</strong>mations include a linear trans<strong>for</strong>mation between RGB <strong>and</strong><br />

Y CbCr color spaces <strong>and</strong> a nonlinear trans<strong>for</strong>mation applied to Y CbCr <strong>for</strong> compensating<br />

the luma dependency. The skin classifier is described by an elliptical region,<br />

which lies in the nonlinearly trans<strong>for</strong>med Y CbCr space.<br />

A.1 Linear Trans<strong>for</strong>mation<br />

Our face detection algorithm utilizes a linear trans<strong>for</strong>mation to convert the color<br />

components of an input image in the RGB space into those in the Y CbCr space <strong>for</strong><br />

separating the luma component from chroma components of the input image. The<br />

trans<strong>for</strong>mation between these two space is <strong>for</strong>mulated in Eqs. (A.1) <strong>and</strong> (A.2) <strong>for</strong> the<br />

value of color components that range from 0 to 255 (see the details in [155]).<br />

153

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