COMPARISON OF THREE COLOUR SPACES IN SKIN DETECTION. Chelsia Amy Doukim, Jamal Ahmed Dargham & Ali Chekima

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1 ONEO SCIENCE 24: MACH 2009 COMPAISON OF THEE COLOU SPACES IN SKIN DETECTION School of Enineein & Infomation Technolo Univesiti Malasia Saah Kota Kinaalu Saah Malasia ASTACT. Skin detection is used as the fist step fo susequent featue etaction in imae pocessin techniques. In this wok the pefomance of skin detection in thee colou spaces; Nomalised G Modified Nomalised G and YCC is investiated. The most famous and lae dataase namel Compaq dataase is used to constuct the histoam model and to test the skin detection aloithm. It was found that the chominance component fom the Modified Nomalised G colou space ave the hihest coect detection ate compaed to the othe two colou spaces. KEYWODS. Skin detection Colou space Histoam thesholdin INTODUCTION Skin detection is an impotant pelimina pocess fo susequent featue etaction in imae pocessin techniques. It has een poved that skin-colou infomation can e used fo detectin human skin in vaious compute vision applications. An appopiate colou space is equied in modellin the skin colou distiution. Man colou spaces have een selectivel used fo modellin the skin colou distiution such as G Nomalised G HSV/HSI/HSLYCC YESYUV and YIQetc.Chaiandouzedoum2000;Yan etal. 1998;Vezhnevets etal Phun et al demonstated the distiution of human skin colous in the YCC colou space modellin it into thee Gaussian clustes fo the human face detection. A stud on the effect of colou space choice on skin detection pefomance was done and a compaison of five colou spaces is povided Zait et al Chai and ouzedoum 2000 poposed an imae classification technique that uses the aesian appoach to classif piels into skin colou and non-skin colou in YCC colou space. Teillon et al pesented the esults of usin colou spaces with sepaated luminance and chominance components which ae moe appopiate fo human face detection. Gomez et al evaluated each component of seveal colou models usin the attiute selection appoach which is well-known in the machine leanin communit to select the suitale colou space fo skin detection. Aliol et al poved that if an optimum skin detecto sstem is desined fo eve colou space then the pefomance of all these skin detectos sstems is the same. Thee ae seveal skin detection aloithms utilizin the histoam ased-appoach to skin piels sementation. These appoaches ae fast in tainin and pactical and ae theoeticall independent fom the shape of skin distiution Vezhnevets et al Zait et al used the colou histoam-ased appoach fo sementin the skin piels that is pojected to wok with a wide vaiet of individuals lihtin conditions and skin tones. Sial et al applied an adaptive colou histoam technique fo eal-time skin sementation in video sequences. Soiano et al emploed the histoam ackpojection technique whee the skin colou model is updated piels in the seach eion that falls in the skin locus. Fan and Qiu 2003 poposed a colou histoam-ased appoach to detect human face and make use of the pincipal component analsis PCA fo oust detection ate. 75

2 76 In this pape the pefomance of skin detection fo the thee colou spaces: Nomalised G Modified Nomalised G and YC C on Compaq dataase ae discussed. The distiutions of skin and non-skin eions ae modelled usin the histoam-ased appoach whee the loal thesholds fo each chominance components in the thee colou spaces ae detemined. These thesholds values ae then used to classif whethe a piel elons to skin o non-skin. The pape is oanized as follows. Section 2 and Section 3 iefl descie the Modified Nomalised G colou space and the YC C colou space espectivel. In Section 4 the dataase used in this wok is descied. Section 5 eplains the methodolo of this wok. Section 6 ives the epeiment esults and Section 7 concludes the pape. The Modified Nomalised G colou space is used in this wok. Fo an imae with M N piels the components fo piel ae iven Equation 1: MODIFIED NOMALISED G COLOU SPACE 1 G G G G } whee and epesent the thee chomaticities of the ed een and lue additive pima colous espectivel. This equation pefoms piel--piel nomalisation of the G components of the G colou sstem. Equation 1 is modified so that the G components ae nomalised the maimum value of G ove the entie imae and is iven Equation 2 Daham and Chekima G G Ma G Ma G G Ma = = = } 2

3 Compaison Of Thee Colou Spaces In Skin Detection YC C COLOU SPACE YCC is the othoonal colou space that educes the edundanc pesent in the G colou channels and epesents the colou with statisticall independent components Kakumanu et al In this fomat the luminance infomation is stoed as a sinle component Y and the chominance infomation is stoed as two colou-diffeence components; C and C. C epesents the lue component and a efeence value while the C component epesents the diffeence etween the ed component and a efeence value. This colou space is consideed as a favouale choice fo skin detection due to the tansfomation simplicit and unamiuous sepaation of luminance and chominance components. THE DATAASE The dataase used in this wok is the famous tainin and test dataase fo skin detection namel Compaq dataase Jones and eh This dataase compises imaes with its coespondin masked imaes. Thee ae two sets of data pepaation the fist one is the data set used to uild the histoam models and the second one is the test data set used to evaluate the pefomance of the skin detection aloithm. The fist data set consists of 100 imaes andoml picked fom the dataase. Fo the testin evaluation 100 imaes wee also andoml picked fom the dataase. METHODOLOGY Pefomance Metics The pefomance metics ae used in ode to detemine which chominance component ields the est skin detection esults. Thee diffeent metics ae used to evaluate the esults of the skin detection aloithms. The %C is the pecentae of the coect skin detection and is iven in Equation 3. The FA False Acceptance ate is the pecentae of identification instances in which false acceptance occus. Fo eample an unauthoized peson is identified as an authoized one. The F False ejection ate is the pecentae of identification instances in which false ejection occus. This is the case when the sstem fails to econize an authoized peson and ejects that peson as an imposto. The FA and F ae epessed in Equation 4 and 5 espectivel. The est chominance in oth colou spaces ae then comined and the effectiveness of the comination is investiated. nume of piels coectl classified % C 100% 3 total piels in the dataase non - skin eo FA 100% 4 total piels in the dataase skin eo F 100% 5 total piels in the dataase 77

4 Skin Detection The histoam-ased sementation appoach is an effective methodolo to skin piel sementation ecause it is fast in tainin and is theoeticall independent of the shape of skin distiution Vezhnevets et al The skin and non-skin histoam models fo the thee colou spaces; Nomalised G Modified Nomalised G and YCC wee constucted usin 100 imaes andoml picked fom the famous Compaq imae dataase espectivel. The coespondin masked imaes wee used as the efeence and as well as the ound tuth when evaluatin the pefomance of the skin detection method. The histoams of skin and non-skin piels fom the chosen imaes wee dawnusinanumeofchominancecomponents:..-and-fothenomalisedg andmodifiednomalisedgandc C C /C C.CandC-CfotheYCC. The chominance components that ave the lowest ovelap etween the skin and nonskin distiutions wee selected fo skin detection on thei espective colou space. Fiue 1 shows an eample of histoams with low ovelap and hih ovelap. Fo each chominance component a loal theshold is selected that minimizes the skin detection eo. The pefomance of the skin detection model was measued ove a test data set compisin 100 imaes andoml picked fom the Compaq dataase with coespondin masked imaes. To pefom the skin detection an imae is fist tansfomed into the colou space. The colou values will indicate the value fo each piel in the imae and if the value falls etween the low theshold and the hih theshold then the piel is classified as skin. Othewise the piel is identified as non-skin. Skin Non-skin Skin Non-skin Fiue 1. Eample of histoam with low ovelap left and hih ovelap iht etween the skin and non-skin distiutions. ESULTS AND DISCUSSION Fiue 2 povides the esults otained fo the Nomalised G colou space. Fom the esults the hihest coect detection is iven the. chominance. The skin detection esult fo the Modified Nomalised G is povided in Fiue 3. Fo this colou space the - chominance ields the hihest coect detection ate with an impovement of moe than 0.1% compaed to the. chominance fom the Nomalised G colou space. Fiue 4 shows the esults fo the YCC colou space. The hihest coect detection ate is otained fom the C chominance althouh it is slihtl lowe than the pefomance iven the - chominance fom the Modified Nomalised G. Tale 1 lists the chominance that ave the hihest coect detection ate fo each colou space. The - chominance fom the Modified Nomalised G colou space anked as the hihest with 81.45% of coect detection. 78

5 Compaison Of Thee Colou Spaces In Skin Detection Nomalised G Tainin Testin Pecentae of Coect Detection Chominance Fiue 2. Pecentae coect detection fo seveal chominance of the Nomalised G colou space on the tainin and testin imaes. Tale 1. The chominance that ave the hihest coect detection ate fom each colou space. Colou Space Nomalised G Modified Nomalised G YC C Chominance. - C Coect Detection ate 69.09% 81.45% 81.31% Modified Nomalised G Tainin Testin Pecentae of Coect Detection Chominance Fiue 3. Pecentae coect detection fo seveal chominance of the Modified Nomalised G colou space on the tainin and testin imaes. 79

6 YCC Tainin Testin Pecentae of Coect Detection C C C/C C.C C -C Chominance Fiue 4. Pecentae coect detection fo seveal chominance of the YCCcolou space on the tainin and testin imaes. CONCLUSIONS In this wok the pefomance of skin detection in the Nomalised G the Modified Nomalised G and the YCC colou spaces was investiated. Histoam-ased appoach is used whee the loal theshold value fo each chominance component was detemined. The - chominance fom the Modified Nomalised G colou space ields the hihest coect detection ate of 81.45% followed the C chominance fom the Nomalised G colou space and finall the. chominance fom the Nomalised G. The esult otained is consideed to e slihtl supeio compaed to the detection ate of 80% otained Jones and eh EFEENCES Aliol A. Toes L. & Delp E.J Optimum Colo Spaces fo Skin Detection. Poceedins of the Intenational Confeence on Imae Pocessin. Octoe Thessaloniki Geece. Chai D. & ouzedoum A A aesian Appoach to Skin Colo Classification in YCC colo space. Poceedins of the IEEE eion Ten Confeence. Septeme Kuala Lumpu Malasia. Daham J.A. & Chekima A Lips Detection in the Nomalised G Colou Scheme. Poceedins of the Intenational Confeence on Infomation and Communication Technoloies.Apil Damascus Sia. Fan J. & Qiu G A Colou Histoam ased Appoach to Human Face Detection. Poceedins of the Intenational Confeence on Visual Infomation Enineein. Jul Sue UK. 80

7 Compaison Of Thee Colou Spaces In Skin Detection Gomez G. Sanchez M. & Luis Enique S On Selectin an Appopiate Colou Space fo Skin Detection. Poceedins of the Second Meican Intenational Confeence on Atificial Intellience: Advances in Atificial Intellience. Apil Queec Canada. Jones M. J. & eh J. M Statistical Colou Models with Application to Skin Detection. Poceedins of the Intenational Confeence on Compute Vision and Patten econition. June Ft. Collins CO USA. Kakumanu P. Makoiannis S. & ouakis N A Suve of Skin-colou Modelin and Detection Methods. Patten econition 403: Phun S. L. ouzedoum A. & Chai D A Novel Skin Colo Model in YCC Colo Space and its Application to Human Face Detection. Poceedins of the Intenational Confeence on Imae Pocessin. Septeme ocheste NY. Sial L. Sclaoff S. & Athitsos V Estimation and Pediction of Evolvin Colo Distiutions fo Skin Sementation Unde Vain Illumination. Poceedins of the IEEE Confeence on Compute Vision and Patten econition. June Hilton Head Island USA. Soiano M. iitta M. Huovinen S. & Laaksonen M Skin Detection in Video unde Chanin Illumination Conditions. Poceedins of the Intenational Confeence on Patten econition. Septeme acelona Spain. Teillon J. C. Shiazi M. N. Fukamachi H. & Akamatsu S. A. A. S Compaative Pefomance of Diffeent Skin Chominance Models and Chominance Spaces fo the Automatic Detection of Human Faces in Colo Imaes. Poceedins of the Intenational Confeence on Automatic Face and Gestue econition. Mach Genole Fance. Vezhnevets V. Sazonov V. & Andeeva A A Suve on Piel-ased Skin Colo Detection Techniques. Poceedins of the Intenational Confeence on Compute Gaphics and Vision. Septeme Moscow ussia. Yan J. Lu W. & Waiel A Skin-Colo Modelin and Adaptation. Poceedins of the Asian Confeence on Compute Vision. Janua Hon Kon China. Zait. D. Supe. J. & Quek F. K. H Compaison of Five Colo Models in Skin Piel Classification. Poceedins of the Intenational Wokshop on econition Analsis and Tackin of Faces and Gestues in eal-time Sstems. Septeme Cofu Geece. 81