生物特征认证

1、生物特征认证技术Skin Color in Face AnalysisChapter 99.5 Modeling Skin ColorsSkin color model is a description of possible skin tones（皮肤颜色模型是描述可能的皮肤色调）（皮肤颜色模型是描述可能的皮肤色调） To create such a model 1，One has to first select the color space in which the model is formed （选择的颜色空间中的模型）（选择的颜色空间中的模型）2，Then the mathemat

2、ical model to describe the possible skin colors（通过数学模型来描述可能的皮肤颜（通过数学模型来描述可能的皮肤颜色）色）3，Finally, the data upon which the model is defined.（最后，定义模型的数据）（最后，定义模型的数据）9.5 Modeling Skin Colors9.5.1 Behavior of Skin Complexions at Different Color Spaces Under Varying Illumination(在不同光照下不同颜在不同光照下不同颜色空间的肤色行为色空间

3、的肤色行为)9.5.2 Color Spaces for Skin(皮肤颜色空间皮肤颜色空间)9.5.3 Skin Color Model and Illumination(肤色模型和光肤色模型和光照照) 9.5.1 Behavior of Skin Complexions at Different Color Spaces Under Varying Illumination（不同光照下的不同颜色空间下的肤色的行为）（不同光照下的不同颜色空间下的肤色的行为） Not all color spaces are equal: they can map RGB values differently

4、, which can be used to separate certain colors.(并不是所有的颜色空间都相等，他们都可以映射得到并不是所有的颜色空间都相等，他们都可以映射得到不同的不同的RGB值，这些值被用来划分确切的颜色值，这些值被用来划分确切的颜色) a color space conversion does not remove chromaticity shifts due to illumination or effects caused by noise.(由于光照和噪声影响而改变的色品不会因为由于光照和噪声影响而改变的色品不会因为颜色空颜色空间的转换而发生改变间的转

5、换而发生改变 ) The brightness control or lack of it can have a strong effect on the possible skin chromaticities.(亮度控制或缺亮度控制或缺乏会对可能的皮肤色品的影响很大乏会对可能的皮肤色品的影响很大)Therefore, the skin colors have been studied under varying illuminations34.（因此，在不同的光照下对皮肤（因此，在不同的光照下对皮肤的颜色进行了研究）的颜色进行了研究）color spacesRGB coordinates

6、are device-oriented, but they can be converted into human vision oriented spaces like XYZ or CIE Lab.(RGB坐标是面向设备的，但它们可以转化为坐标是面向设备的，但它们可以转化为人视觉化空间人视觉化空间XYZ或或CIE)A correct conversion requires an illumination-dependent transform matrix, including also the effect of device characteristics.(一个正确的转换需要一个照明

7、一个正确的转换需要一个照明相关的变换矩阵，包括设备特性的影响。相关的变换矩阵，包括设备特性的影响。)Based on the conversion method, into two groups: those using linear transforms from RGB and those obtained via non-linear transforms(基于转换的方法，分基于转换的方法，分为两组：那些使用线性非线性变换从为两组：那些使用线性非线性变换从RGB得到得到)BGR18.214-93.786-112.00112.0074.207-37.797-24.966128.55365.

8、48112812816CrCbY color spacesthe linear transform: I1I2I3, YES, YIQ, YUV, YCrCbthe nonlinear transforms are:NCC rgb, modified rgb, HSV, HSL9.5.2 Color Spaces for SkinSeveral color spaces have been suggested for general skin color modeling, but thus far, none of them has been shown to be superior to

9、the other(几个颜色空间已几个颜色空间已经提出了一般的皮肤颜色建模，但到目前为止，他们没有经提出了一般的皮肤颜色建模，但到目前为止，他们没有被证明是优于其他。被证明是优于其他。).However,it seems that those spaces in which intensity is not separated so clearly from chromaticity are similar to RGB.(然而，那些空间，分离色度相似的然而，那些空间，分离色度相似的RGB强强度不是很明显度不是很明显)The separation of color spaceThe separ

10、ation can be evaluated using linear or linearized RGB data.(那种那种分离可以使用线性或线性化分离可以使用线性或线性化RGB数据进行评估数据进行评估)R cR(替代替代)G cGB cBc describes a uniform change in the intensity levels. (c描描述的强度水平的均匀变化。述的强度水平的均匀变化。)注意：注意：(If the factor c does not cancel out for chromaticity descriptors, the separation is inco

11、mplete)Normalized color coordinates (NCC)Normalized color coordinates (NCC) are quite often used in modeling, and they separates the intensity and chromaticityThe performance of NCC and CIE xy was superior to several other skin color models. It was also shown that NCC has a good discrimination power

12、.(NCC和和CIE xy的性能要优于其他几种肤色模型。也正是在的性能要优于其他几种肤色模型。也正是在 55 表明，表明，NCC具有良好的识别能力具有良好的识别能力)BGRGgBGRRr1rbgNCC的色彩空间9.5.3 Skin Color Model and Illumination Illumination affects skin color both in canonical and uncanonical images(光照影响标准与非标准图像的肤色光照影响标准与非标准图像的肤色)the camera sensors and internal image preprocessing

13、 of the camera affect the color production(相机传感器和摄相机传感器和摄像机内部图像预处理对彩色图像的影响像机内部图像预处理对彩色图像的影响)聚类特性9.5.3 Skin Color Model and Illumination illumination affects skin color both in canonical and uncanonical images(光照影响标准与非标准图像的肤色光照影响标准与非标准图像的肤色)the camera sensors and internal image preprocessing of the c

14、amera affect the color production(相机传感器和摄相机传感器和摄像机内部图像预处理对彩色图像的影响像机内部图像预处理对彩色图像的影响) Therefore, creating a universal model is difficult. (因此，创建一个通用模型是困难的。因此，创建一个通用模型是困难的。)Color correction based approach has been suggested基于色彩校正的方法基于色彩校正的方法 The colors in image are corrected so that the skin would appe

15、ar in skin tones and after this segment the image using skin color model.(用肤色模型分割图片之后，用肤色模型分割图片之后，图像中的颜色被校正使得肤色出现在肤色色调上图像中的颜色被校正使得肤色出现在肤色色调上) The color correction is based on a pixel with a high brightness value which are assumed to belong to a white object. (颜色校正是基于一个高亮度帧，这一帧被假颜色校正是基于一个高亮度帧，这一帧被假定属

16、于一个白体定属于一个白体)These pixels are used to calculate correction coefficient which are applied to the image(这些像素被这些像素被用来计算适用于图像的校正系数用来计算适用于图像的校正系数) Color correction based approach has been suggested基于色彩校正的方法基于色彩校正的方法This approach can fail for many reasons like data loss due to saturation, or if a pixel wi

17、th high brightness belongs to a nonwhite objectwithout the color correctionThe segmentation with their color correction method. use the knowledge illumination changes calibration camera settings The drawback of this modelIt is not so specific as canonical modelsmore color tones are included(作为权威模型，它并不是具体的，它作为权威模型，它并不是具体的，它包含了很多颜色色调包含了很多颜色色调). Thus, more nonskin obje