OBJECT TRACKING AND POSITIONING ON VIDEO IMAGES

Transcription

1 OBJC RACKIG AD OIIOIG O VIDO IMAG Ch-Far Che, M- Che Ceter for pae ad Remote eg Reearh, atoal Cetral verty, Chug L, AIWA fhe@rr.u.edu.tw 55 Commo ICWG V/III KY WORD: Vdeo, arget, rakg, Objet, Mathg ABRAC: h tudy preet a applato of dgtal vdeo amera for objet trakg ad potog. he ma purpoe of the tudy to automatally trae ad poto a motole objet o the vdeo mage that are reorded o a movg vehle. Beaue of the hage of the foal legth of amera ad the movemet of the vehle, the appearae of a motole objet o the vdeo mage frtly wll gradually hage t hape ad ompletely loe t trae after a perod of tme. he varato of the hape apparetly wll brg about the omply for developg the automated algorthm to trae ad poto objet o the vdeo mage. I th tudy, we develop a hape-baed trakg tehque to mplemet the trakg tak. he tehque ue the hape matrx algorthm MA that ha ale ad rotato varat haratert to alulate the mlarty of varat hape betwee adjaet vdeo frame. After the objet traed every vdeo frame, the photogrammetr ollearty odto equato are ued to traform the objet from the mage oordate to the groud oordate. A expermet performed to trae a motole hp the ope ea. he reult how that the propoed method a uefully trae ad poto the hp eve the hp had beome etrely out of hape o the vdeo mage.. IRODCIO Reetly the dgtal vdeo DV amera ha beome a popular motorg tool beaue t maller, lghter ad eaer ug tha tradtoal oe. By ombg DV wth a movg vehle e.g., helopter or arplae, t a reord a equee of mage oveetly ad effetvely. h tudy preet a delate algorthm that a automatally trae ad poto a motole objet o the vdeo mage, whh are reorded o a movg helopter. he propoed method may be dvded to three equet tep: the aquto of the poto ad agular oretato of the amera; the etmato of the mage oordate of the objet; 3 the otruto of the groud oordate of the objet. he frt tep deged to fd out the poto ad agular parameter of the vdeo amera. I order to meet the trt ad omplex reordg evromet o the helopter, a hardware ytem tegrate tlt-meter, G, ad dgtal ompa wth DV developed th tudy. he ma futo of the ytem to reord the vdeo mage ad the amera oretato yhroouly. he eod tep to etmate the mage oordate of the objet o the vdeo mage. he ma goal of the tep to mplemet the tak of objet trakg o the vdeo mage. e the objet our tudy hage the hape all the way the reordg perod, th tudy ue olor-baed egmetato e, 999 ad hape-baed mathg algorthm Fluer, 99; Fluer, 995 to trae ad loate the objet. he fal tep to alulate the groud oordate of the objet o the mage equee. Lkg up the amera oretato from teop wth objet mage oordate from tep, the ollearty odto equato a be ued to alulate the groud oordate of the objet. he orgazato of th paper a follow. eto trodue the formato of the hardware ytem. eto 3 derbe the propoed objet egmetato proe. I eto 4, the hape-baed objet mathg ad trakg tehque are how detal. he potog method wll be how eto 5. Fally, the expermet reult ad oluo are addreed eto 6 ad eto7.. ARDWAR YM I order to reord the vdeo mage ad oretato formato of the amera yhroouly, wherefore th tudy tegrate G, dgtal ompa ad the tlt meter wth DV through a eoded-deoded hardware deve. he type of dgtal vdeo amera ued reordg data OY C5. he auray of the tlt meter /- wth a rage of /- from the horzo, the auray of the dgtal ompa about /- 3, ad the G auray about ~5 meter. he tegrated ytem baally trafer the oretato data from dgtal format, aqure from the deve metoed above, to aalog voe. herefore the vdeo data ad oretato parameter a be reorded through both vdeo ad audo hael yhroouly. vetually, after the reordg proedure aomplhed, by makg ue of the deoded deve ad Mrooft DretX ompoet, the amera oretato ad the orrepodg vdeo gal a be reotruted from aalog data to dgtal mage. 3. OBJC GMAIO

2 I th eto, the detal of objet egmetato method wll be preeted. Dmlar to the trakg objet o the uhagg bakgroud, t dffult to ue mple dfferetatg method to egmet the objet o the vared bakgroud. herefore, we ue two-tage egmetato proedure to trak the objet o a equee of mage. he frt tage ue the olor feature to egmet poble rego of the target objet from the mage. he eod tage employ Atve Cotour Model to derbe the otour hape of the target objet. 3. he Color Feature egmetato I the early perepto tage of huma beg, mlar olor are alway grouped together for further aaly. Baed o th aumpto, dered objet a be detfed by ratg the haratert olor a the feature. I th tudy, the dered objet maually eleted by mea of markg a rough polygo the very frt mage. he a uuperved lafato method ued to rat major olor lae of the objet ad bakgroud. Aordgly, thee olor lae a be ued to egmet the objet or bakgroud o the mage. he followg are the bref derpto of the method. For a gve pxel oe of pxel the earh wdow o mage. {O } the la eter of the objet ad {B } the la eter of bakgroud. the threhold of petrum dtae. If.Mmum Dtae to {B }< belog to bakgroud la. If.Mmum Dtae to {O }< belog to objet la. le a part of bakgroud la. After the olor-baed egmetato fhed, t poble to obta a bary mage wth objet eparated from bakgroud. ormally, the dered objet egmet hould be a old rego; therefore, the eroo, dlato ad eght-eghbor objet labelg algorthm are employed to elmate the error pxel. Moreover, t eeary to derbe the objet a a loe otour, a eergy-mmzg edge egmetato algorthm, whh appled to repreet the hape of the objet, wll how ub-eto. 3. hape Feature xtrato Atve Cotour Model ACM Ka, 987 oe kd of parametr urve preetato, whh defed wth a urve doma. he urve of ACM a move uder the fluee of teral fore aue by the tal urve ad eral fore uppled by mage data. ACM wdely ued mage proeg applato, uh a edge deteto, egmetato ad partularly to loate objet boudare. ACM trafer the boudary deteto problem mage doma to eergy-mmzg problem urve doma. he tradtoal eergy futo ACM are defed a follow: ake = = t t = β Where α = f 3 ake = the ake eergy of the otour. = the th poto of otour. = umber of axel. t = the teral eergy at axel. = the eral eergy at axel. α, β = the weghtg futo are defed to otrol the relatve mportae of the elat ad bedg term. radtoal ACM ha two problem, talzato ad overgee oave rego. he talzato problem mea that the tal otour ha to loe to the objet, beaue the potetal fore of tradtoal ACM geerally mall. Due to the ACM ha o ra preure fore o oave rego, the otour ofte aro the boudary oave. I order to olve the problem, a ra eral fore, whh amed Gradet Vetor Flow GVF Xu ad re, 998 a be ued to mprove the reult of ACM. GVF a dffuve fled, whh omputed by gradet vetor of a gray-level map derved from the mage. Whe the pot the feld ear to objet boudary, the GVF feld wll move toward the boudary. Moreover, GVF feld wll hage moothly the homogeou rego of the mage. herefore, t date that GVF ot oly a provde a larger buffer tal otour but alo a overge to the oave rego. By ug GVF Atve Cotour Model, the hape of poble objet, whh are egmeted by olor feature o mage, a be rated automatally. Fg. how the flowhart of objet egmetato. 4. A-BAD OBJC MACIG AD RACKIG It mut be oted that the olor egmetato may geerate a umber of poble objet o the ubequet mage. Moreover, the movemet of the vdeo amera deftely wll keep hagg the hape of the objet. Apparetly both varou poblte ad vared hape of the objet wll brg about the omply for trakg the dered objet o the ubequet mage. h tudy ue the hape derved from ACM alog wth hape Matrx Algorthm MA to trae the dered objet betwee adjaet mage.

3 Fg. Objet G the mage doma. Fg.3 hape of objet G a be reotruted from MA. he fator K fluee the auray of mlarty; the hgher K a derbe the hape more exhautvely. Coderg avg the ompute tme, we et K=3 th tudy. By ug MA, the mlarty betwee two objet a be alulated, aordgly, the objet rego o the mage a be foud too. MA ot oly fd the mot mlar objet o the mage, but alo fgure out the dfferee of alg ad rotato betwee the two hape. 4. Feature ot rakg Fg. Flow hart of objet egmetato. 4. hape-baed Mathg MA a kd of varat hape derpto, whh defe the gravty eter of objet a the org ad the loget ax of objet a ma ax. he hape of objet o the mage a be reotruted aa a hape matrx from MA Fg., Fg.3. By omparg the hape matrx B O wth B O, the degree of mlarty betwee two objet O ad O a be alulated. Beaue the dmeo of the matrxe have to be equal, hee the dmeo of the matrx ad the mlarty p B O, B O are defed by followg formula: = K max[max d A,,max d A, ] 4 * O O A O A O O O O O p B, B = Bj Bj 5 j= = Where da, = the dtae from A to. K = the mlarty auray fator. he hape rego a be rated automatally by preedg tep, oequetly, the tep to trak the feature pot of the objet. he area-baed mathg algorthm a math pot feature preely, everthele, the ue of area-baed mathg algorthm hghly deped o the varae of the target wdow ad earh wdow. By mea of the oeffet of MA, t poble to elmate the hape hage of the objet. vetually, the eter poto of the bet mathg blok whh wth hghet probablty the trakg reult. he ze of target blok 7 by 7 th reearh, ad the target blok gve by the reult of DGO Lue, 988. DGO a teret operator, whh a fd the mot obvou feature pot the mage. he boudary of earh wdow deded by the objet boudary retagle o the mage. h tudy elet the Mea quare rror M to be the objetve futo of area-baed mathg. M meaure the magtude of error a a reult of two blok omparo, lower error mea hgher probablty of two blok are mlar. he detal of M are how a follow.

4 Let B pq the addate blok wth poto p,q mage ad r the target blok wth poto r, urret mage. he Mea quare rror of two blok gve a: = = = M j j r j pq r pq B M B M, 6 Where: M, are the dmeo of the blok.,j repreet the poto of pxel blok. 5. OBJC OIIOIG A metoed before, the oretato of the amera a be obtaed from the hardware ytem, furthermore, the hape-baed mathg ad feature pot trakg a be ued to ompute the mage oordate of the objet. Coequetly, for eah mage that ha oretato data, wll gve re to et three equato. hee wll be derved from the followg relatohp betwee the reordg poto ad the objet loato loal geodet ytem,,. = 7 where = arget poto vetor [ ] = he th frame poto vetor [ ] = alg fator of th frame = he ut vetor potg from the amera to the target of th frame [ ]. It a be how a = R FB Ob / Ob, where R FB = R FB a rotato matrx ad ue the horthad for o ad for. If there are mage that have oretato data, t wll 3* equato ad 3 ukow. he ukow lude the objet three dmeo oordate ad alg fator. he leat quare adjutmet utable to olve the followg lear equato. 3] ][ 3 [ [ 3][] = ][] 3 [ 6. XRIM RL AD COCLIO he expermet of th tudy wa deged to trae ad poto a motole hp ear the oat. he vdeo mage were reorded at a frame rate of fp ad wth mage ze of about 3 pxel by 4 pxel. he groud urvey wa alo ued to obta the oordate of the hp that wll be ued a the auray hek. A part of the trakg reult are how Fg.4 a, Fg. 4b ad Fg. 4. he red otour o the mage repreet the reult of trakg, ad the gree ro the reult of feature pot trakg. he reult date that eve though the hape of the objet hage etrely, the propoed algorthm ot oly a trae the otour of hp, but alo a trae the feature pot o the hp. he groud oordate of feature pot o hp are alo alulated by the ollearty equato. A poto omparo made betwee the feature pot o the hp from the vdeo mage ad the hp telf from the groud urvey. he omparo date that a poto drepay of about 35 meter a be foud. he poto drepay baally a be attrbuted to the lmted preo of the oretato reordg deve. owever, f the poto of hp lude the rage of the whole hp body the hp ha the legth of at let meter, the poto drepay a be odered aeptable. Fgure 4a. mage

5 Lue, Y., 988. Iteret Operator ad Fat Implemetato, Iteratoal. Arhve of hotogrammetry ad Remote eg, Iteratoal Arhve of hotogrammetry ad Remote eg, e,. C, 999. xtratg Color Feature ad Dyam Mathg for Image Data-Bae Retreval. I raato o rut ad ytem for vdeo tehology, vol. 9, O 3. Fgure 4b. 47 th mage Xu, C. ad J.L. re, 998. ake, hape, ad gradet vetor flow I ra Image ro. Vol 7,pp Xu, C. ad J. L. re, 998. "Geeralzed Gradet Vetor Flow xteral Fore for Atve Cotour", gal roeg A Iteratoal Joural, vol. 7, o., pp Fgure th mage 7. COCLIO I th tudy, we have preeted the olor-baed ad hape-baed algorthm for objet trakg ad potog o the vdeo mage reorded from a movg helopter. he method ue olor feature a the ba to egmet the dered objet o the mage ad the employ hape feature to trak the objet ad poto the feature pot of the objet o every mage frame. he feature pot of the objet the traformed to the groud oordate wth the ad of the oretato parameter of the amera. he poto reult from the vdeo mage ompared wth that of the groud urvey. he quattatve aemet date that the propoed method a poto the objet o the vdeo mage wth the aeptable level of the auray. 8. RFRAC Fluer, J., 99. Ivarat hape Derpto ad Meaure of Objet mlarty., I : 4th Iteratoal Coferee o Image roeg ad t Applato. I Coferee ublato 354. I, pp Fluer J., 995, Objet mathg by mea of mathg lkelhood oeffet, atter Reogto Letter, 6,pp Ka, M. A. ad D. erzopoulo, 987. ake: Atve otour model, ro. t Iteratoal Coferee Computer Vo, Lodo, pp