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1、基于U-V空间的人脸检测方法曹曼曼（济宁学院 计算机科学系 山东 曲阜 273155）摘要：本文提出了一种基于U-V空间的人脸检测方法。该方法首先根据YUV彩色模型建立，忽略了其非主要的亮度分量来对肤色进行分割，其次建立了唇色模型，提高了肤色和嘴唇的检测正确率。关键词：YUV彩色空间，肤色模型，唇色模型，肤色分割A Face Detection Method Based On U-V Color SpaceCao Man-man(Computer science department JiNing university Qufu Shandong 273155)Abstract: This p
2、aper presents a face detection method based on U-V color space. First, skin-color model is established based on YUV color space, ignorde the nonprincipal brightness component to make the skin color segmentation, next, lip color model is established, the performance of face and lip detection has been
3、 improved.Key words: YUV color space, skin model, lip color model, skin-color detection1引言人脸对于背景而言有其独特的色彩分布，对于人脸的检测而言，其首要工作1在于搜寻肤色区块，然而肤色分割容易受到环境亮度的影响，尤其在分辨率略差或是其它成像条件影响下，我们会发现在亮度偏高的环境中人脸肤色部分易接近白色，而亮度低的地方也可能成为阴影或接近黑色，这将大大影响计算机系统对人脸的检测。本文使用YUV彩色模型建立肤色模型，忽略了其非主要的亮度分量来对肤色进行分割，从而肤色分割不会因为不同人种的肤色而受任何影响，提高
4、了肤色检测的正确性，将(Y,U,V)彩色坐标的三维计算降低到二维(U,V)运算，运用这种方式提高了运算速度。2肤色模型的建立本文以像素点深浅不同的肤色组合资料集作为样本，如图(1),经过色彩模型2转换图(1) 50K像素点之不同肤色样本后如图(2)所示，从坐标图中可以清楚发现，肤色集中分布在其中的象限上，因此可以归纳出肤色阈值条件为一角的扇形集中区域，并以此作为肤色的分别范围，在求扇形肤色阈值之前，必需先求得扇形夹角以及夹角的长度，如公式(1)-(2)所示。图(2) 彩色模型中肤色的分布图扇形肤色阈值公式： (1)以及 (2)为了验证亮度变化对此肤色分割方式对影响程度，本文做了以下实验证明：以
5、肤色满值时的亮度彩色分量Y设定为基准值，并大幅度调整Y值补偿作为亮度变化的测试条件(亮度分量Y值取值范围介于之间)，亮度变化调整之后将其还原成彩色模型RGB影响并重新作为肤色分割测试的输入，依次记录肤色检测覆盖率对亮度变化的影响，结构如表1所示，由表显示肤色检测覆盖率在亮度变化率区间约范围内仍然保持稳定。本文运用此技术于室内、室外的照片，其肤色分割测试结果可参考图(3)所示。由肤色检测覆盖率在亮度变化率区间约为范围内仍然维持稳定。我们运用此技术处理在室内、室外多人照图像，其肤色分割测试结果如图(4) 所示。图(3) 亮度变化对肤色检测覆盖率的关系图图(4) 室内(a)(b)与室外(c)(d)图
6、像的肤色切割3唇色切割如同肤色，唇部3为特征中颜色最明显而且容易辨认的特征4 5，因此使用颜色分割最合适，与肤色分割原理相同，我们希望肤色与唇色分割能在同一演算时间内完成，以增加测试速度，我们收集了13K像素点的不同唇色样本作为唇色分割的测试，如图(5)所示。唇色在UV彩色坐标的分别如图(6)所示，与肤色分布相比较，唇色的分布较前者靠近彩色坐标的U轴。使用UV彩色模型切割彩色图像唇色公式如公式(3)所示。图(5) 13K像素点下不同的唇色样本图(6) UV彩色模型中唇色的分布图扇形唇色阈值公式： (3)4 分析与结论 由2、3部分所介绍的肤色、唇色分割演算法，我们可以成功分割出肤色及唇色区域，
7、其计算结果分别以橘、红色代表，如图(7)所示： A B图(7) A:原始图像 B:肤色与唇色分割的图像本文所述肤色切割的方法能缩小人脸特征的搜索范围，方便了以后的人脸检测或其它人脸相关处理。实验结果表明，本文所提出的肤色模型具有即时性、实用性和普遍性等特点。参考文献1 艾海舟, 武勃. 数字图像处理分析与机器视觉M. 人民邮电出版社出版社，2003.2 梁路宏, 艾海舟, 徐光祐, 等. 人脸检测研究综述J . 计算机学报, 2002, 25 (5) : 449 - 458.3 张欣, 徐彦君, 等. 彩色图象中主要人脸特征位置的全自动标定J . 中国图像图形学报, 2000, 2 (5) :
8、 138 - 143.4 彭波, 崔永普, 黄丹霞, 等. 基于肤色和唇色信息的人脸检测方法的研究J . 计算机工程与设计, 2006, 2 6(6) : 1500 - 1502.5 Hsu R L, AbdelMottaleb M, Join AFace detection in color imagesJIEEE Transactions on Pattern Analysis and Machine Intelligence, 2002, 24（5）：696-706.Editors note: Judson Jones is a meteorologist, journalist and
9、 photographer. He has freelanced with CNN for four years, covering severe weather from tornadoes to typhoons. Follow him on Twitter: jnjonesjr (CNN) - I will always wonder what it was like to huddle around a shortwave radio and through the crackling static from space hear the faint beeps of the worl
10、ds first satellite - Sputnik. I also missed watching Neil Armstrong step foot on the moon and the first space shuttle take off for the stars. Those events were way before my time.As a kid, I was fascinated with what goes on in the sky, and when NASA pulled the plug on the shuttle program I was heart
11、broken. Yet the privatized space race has renewed my childhood dreams to reach for the stars.As a meteorologist, Ive still seen many important weather and space events, but right now, if you were sitting next to me, youd hear my foot tapping rapidly under my desk. Im anxious for the next one: a spac
12、e capsule hanging from a crane in the New Mexico desert.Its like the set for a George Lucas movie floating to the edge of space.You and I will have the chance to watch a man take a leap into an unimaginable free fall from the edge of space - live.The (lack of) air up there Watch man jump from 96,000
13、 feet Tuesday, I sat at work glued to the live stream of the Red Bull Stratos Mission. I watched the balloons positioned at different altitudes in the sky to test the winds, knowing that if they would just line up in a vertical straight line we would be go for launch.I feel this mission was created
14、for me because I am also a journalist and a photographer, but above all I live for taking a leap of faith - the feeling of pushing the envelope into uncharted territory.The guy who is going to do this, Felix Baumgartner, must have that same feeling, at a level I will never reach. However, it did not
15、 stop me from feeling his pain when a gust of swirling wind kicked up and twisted the partially filled balloon that would take him to the upper end of our atmosphere. As soon as the 40-acre balloon, with skin no thicker than a dry cleaning bag, scraped the ground I knew it was over.How claustrophobi
16、a almost grounded supersonic skydiverWith each twist, you could see the wrinkles of disappointment on the face of the current record holder and capcom (capsule communications), Col. Joe Kittinger. He hung his head low in mission control as he told Baumgartner the disappointing news: Mission aborted.
17、The supersonic descent could happen as early as Sunday.The weather plays an important role in this mission. Starting at the ground, conditions have to be very calm - winds less than 2 mph, with no precipitation or humidity and limited cloud cover. The balloon, with capsule attached, will move throug
18、h the lower level of the atmosphere (the troposphere) where our day-to-day weather lives. It will climb higher than the tip of Mount Everest (5.5 miles/8.85 kilometers), drifting even higher than the cruising altitude of commercial airliners (5.6 miles/9.17 kilometers) and into the stratosphere. As
19、he crosses the boundary layer (called the tropopause), he can expect a lot of turbulence.The balloon will slowly drift to the edge of space at 120,000 feet (22.7 miles/36.53 kilometers). Here, Fearless Felix will unclip. He will roll back the door.Then, I would assume, he will slowly step out onto s
20、omething resembling an Olympic diving platform.Below, the Earth becomes the concrete bottom of a swimming pool that he wants to land on, but not too hard. Still, hell be traveling fast, so despite the distance, it will not be like diving into the deep end of a pool. It will be like he is diving into
21、 the shallow end.Skydiver preps for the big jumpWhen he jumps, he is expected to reach the speed of sound - 690 mph (1,110 kph) - in less than 40 seconds. Like hitting the top of the water, he will begin to slow as he approaches the more dense air closer to Earth. But this will not be enough to stop
22、 him completely.If he goes too fast or spins out of control, he has a stabilization parachute that can be deployed to slow him down. His team hopes its not needed. Instead, he plans to deploy his 270-square-foot (25-square-meter) main chute at an altitude of around 5,000 feet (1,524 meters).In order
23、 to deploy this chute successfully, he will have to slow to 172 mph (277 kph). He will have a reserve parachute that will open automatically if he loses consciousness at mach speeds.Even if everything goes as planned, it wont. Baumgartner still will free fall at a speed that would cause you and me t
24、o pass out, and no parachute is guaranteed to work higher than 25,000 feet (7,620 meters).It might not be the moon, but Kittinger free fell from 102,800 feet in 1960 - at the dawn of an infamous space race that captured the hearts of many. Baumgartner will attempt to break that record, a feat that boggles the mind. This is one of those monumental moments I will always remember, because there is no way Id miss this.
