1、SIFT特征提取算法詳解SIFT特征提取算法總結主要步驟1）、尺度空間的生成2）、檢測尺度空間極值點3）、精確定位極值點;4）、為每個關鍵點指定方向參數；5）、關鍵點描述子的生成。尺度克同拋生蕉尺廢空間理論目的是惶齷鐐數局的要尺度特fit.iW斯塞蹦是實現尺度變換的唯Trtfe.予是一同二隼圈隙的尺度空間定義Lx,y.cr）G（x.ytcr）*/（x,j.）其中一gj.cr）是尺度可梟/本心股1.471.L''.'r'工Ttr0（.y）是交間里標曾是尺度坐標的大小決定昭弊的平滑慢度r大尺度對應圖瞰的慨貌恃抵；小尺酬心口像的細節恃SL大曲值對宓相忸尺度（低分辨罩）

2、.反渴正精細尺直僖分測路網m引或或分尺度w間舊。g和:才出沖金分。與J；6=（G七F幽-tX，V.1；e）*/（XV）="X,JLfer）-2（.七4b）L（x,y,o-）,o-=1.6agoodtradeoffinstrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestand-alonetrialsscheduled,withtheprocesspreparationoftestsolutions,equippedwit

3、hprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.constructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheacceptancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificat

4、ionSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T352020046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweldingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe

5、6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequalificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingop

6、erations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstructureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilitya

7、pprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.D(x,y,o-),o-=1.6agoodtradeoffinstrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalone

8、trialsscheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandthea

9、cceptancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipeline

10、weldingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedu

11、requalificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteels

12、tructureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.關于尺度空間的理解說明:圖中的2是必須

13、的，尺度空間是連續的。在Lowe的論文中，將第0層的初始尺度定為1.6，圖片的初始尺度定為0.5.在檢測極值點前對原始圖像的高斯平滑以致圖像丟失高頻信息，所以Lowe建議在建立尺度空間前首先對原始圖像長寬擴展一倍，以保留原始圖像信息，增加特征點數量。尺度越大圖像越模糊。4 nGriUliSidn 0DG J降采樣得到（如2）nextoctave是由firstoctave2Tg.kok'b:k'fb）上二2%尺度空間的所有取值，s為每組層數，一般為35在DOCX度空間下的極值點檢例尺度空同硬低點F丁手粒尺&三司的蔓值口，拒一個三件點要和個"有的相部點比校,看其是

14、否比它的圖驟域和用翻閔相部點大戒者小.如區.不同然吟測電和它同尺度的8小相曾二F帽銅尺.爸"底的9*我電步茂個點曦.以痛保在尺度空圖和工國修堂間都住惻到超值點.如累一個,瑞在口。物度壬聞t理4馬上F網層的26八酒瓶牡是最大或最小值時.就認為誤點是圖埋在該尺痍下的一個樗任員Q同一組中的相鄰尺度（由于k的取值關系，肯定是上下層）之間進行尋找instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalonetrials

15、scheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheaccepta

16、ncespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweldin

17、gproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequal

18、ificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstructu

19、reweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.在極值比較的過程中，每一組圖像的首末兩層是無法進行

20、極值比較的，為了滿足尺度變化的連續性，我們在每一組圖像的頂層繼續用高斯模糊生成了3幅圖像,高斯金字塔有每組S+3層圖像。DO陵字塔每組有S+2層圖像.instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalonetrialsscheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledwor

21、kers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheacceptancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionan

22、dtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweldingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-

23、MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequalificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstructio

24、n,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstructureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewith

25、inthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.通過哪三維二次性融以精蝎網定關植威駒位置源度（這手畫博素精度同時去除低對闿S的關鍵良剎不楣定的邊緣響應點,因為DOG算子會產生軟老的辿族呵匠），以圖箱匹叱便定旦.苣方忖師生挹J，R空間尺度通鞅11)IMj；工，&2&*親導3H算為。

26、13到精琳的位室次-值在己及檢測到的捋征點中要去掉（0對比庶居而怔最壞穗定的邊舞喧瞪點.鏘低對比度的點上把公式（2戕人公式（11只翱耐項可得，1>jVJ?r-Ivcr-+-yX=(x,y.af2&若喬。嗎談特征點就保留下來否則舍科醛埠響座的瑞.一個定義不好的高斯差分算子的極值礎聘邊部的地方有較大的主曲本.而在垂直邊算的方向有軟石州主向電主曲本通過一個丁工7的Ha筋相牛沖莖上f口D1ff=+'=DfD1,L®«身裁由采樣點相鄰差估tt得到.D的主曲率和H的特亞值成正比.力最大特征值.耳為量”的恃征值.迎| l' f I | I -"J

27、J. 一 內即 N W”U IIII « I i11II-=Flpi+%=ei*'i令S-Rr貝"iIfratio>(r+1)2/(r),throwitout(SIFTusesr=10)表示DOG&字塔中某一尺度的圖像x方向求導兩次通過擬和三維二次函數以精確確定關鍵點的位置和尺度（達到亞像素精度）,instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalonetrialssch

28、eduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheacceptance

29、specificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweldingpr

30、oceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequalifi

31、cationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstructurew

32、eldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.為每個關鍵點指定方向參蚣刎以關犍點都城鐮素的悌度方向分布

33、持性為法個關鍵電指定方間參班變單于具善芯轉齊變忖RCidJ-tUw缸工晴Nhjz+D-Ki-LxM)式中出漢力姓憐芟的國道如內間公式嚴其中時用的尺度為福個美維點臺自斫在晌尺度.一至比，圖球的美硬點已喊完畢,每廣寺提點有二個倍品心系所處尺度.方向.由此可以碉定一個8格喃詼域.直方圖中的峰值就是主方向，其他的達到最大值80%勺方向可作為輔助方向IdentifypeakandassignorientationandsumofmagnitudetokeypointTheusermaychooseathresholdtoexcludekeypointsbasedontheirassignedsumofm

34、agnitudes.利用關鍵點鄰域像素的梯度方向分布特性為每個關鍵點指定方向參數，使算子具備旋轉不變性。以關鍵點為中心的鄰域窗口內采樣，并用直方圖統計鄰域像素的梯度方向。梯度直方圖的范圍是0,360度，其中每10度一個柱，總共36個柱。隨著距中心點越遠的領域其對直方圖的貢獻也響應減小.Lowe論文中還提到要使用高斯函數對直方圖進行平滑，減少突變的影響instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalonetria

35、lsscheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheaccep

36、tancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweld

37、ingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequ

38、alificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstruc

39、tureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.關鍵點描述子的生成步驟旋轉主將坐揉軸旋轉為關鍵

40、點的方向，以硅.蜂旅華不變爛生成描 述子它于一.卜H淳古丁二128卜文據,M最終形或128絕的SIFT特征店量將特工亢量由姓笠臼一化.則可以進一步去除光照變化的影響.通過對關鍵點周圍圖像區域分塊，計算塊內梯度直方圖，生成具有獨特性的向量，這個向量是該區域圖像信息的一種抽象，具有唯一性。關鍵點撰述十的生成首光書坐標旗耨為關慨氨的方向.以源保簟輔就性.以特征點為中心里8彝鄰域作為崇祥窗口，將崇祥點與特髭您的相前方向通工高勘印在后閂入巨吉R個K同直方圖，呆后濱得29”8的8羅特於攔苜二.不苣困也下，訕y 卯依疔心巾ticst npior每一個小格都代表了特征點鄰域所在的尺度空間的一個像素，箭頭方向代

41、表了像素梯度方向，箭頭長度代表該像素的幅值。然后在4X4的窗口內計算8個方向的梯度方向直方圖。繪制每個梯度方向的累加可形成一個種子點。instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalonetrialsscheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toe

42、nsuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheacceptancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacce

43、ptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweldingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-r

44、esistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequalificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidet

45、hewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstructureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthesco

46、peandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.每個直方圖有8方向的梯度方向，每一個描述符包含一個位于關鍵點附近的四個直方圖數組.這就導致了SIFT的特征向量有128維.（先是一個4X4的來計算出一個直方圖，每個直方圖有8個方向。所以是4X4X8=128維）將這個向量歸一化之后，就進一步去除了光照的影響。旋轉為

47、主方向instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,theinstrumentaccordingtothestandalonetrialsscheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6

48、.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelineweldingengineeringconstructionandtheacceptancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturestee

49、lweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andironnickelalloyandnickelalloypipelineweldingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldprep

50、aration6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmethods,providingqualifiedweldingprocedurequalificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,m

51、ustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6.2.4whereinvolvedinthepipeandsteelstructureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepa

52、rtmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingtheweldingprocess.工2A雄美健點描述于生或步Jft勒之計玨述F所名的圖像坦墩留述于梯度方向比牙盤由關鍵點所旄又腐的模糊用體計”產生.明停回聯的串在通道下式計R：加父,上*3-1，+1mdw-=-=2G門算美所后維（oC”E）的頓內尺龍,=4instrumenthasasingletestcondition,willbetransferredtothecoordinationofthetestphase,th

53、einstrumentaccordingtothestandalonetrialsscheduled,withtheprocesspreparationoftestsolutions,equippedwithprofessionaltechniciansandskilledworkers,toensuresafetyandquality.6.weldingengineeringconstructionprogramme6.1thisengineeringusedconstructionspecification6.1.1siteequipment,andindustrialpipelinewe

54、ldingengineeringconstructionandtheacceptancespecificationGB50268-976.1.2oilchemicaltoxic,andcanburningmediapipelineengineeringconstructionandtheacceptancespecificationSH3501-20026.1.3oilchemicallowtemperaturesteelweldingproceduresSH/T3520-20046.1.4oilchemicalchromenickelAustrian'sbodysteel,andir

55、onnickelalloyandnickelalloypipelineweldingproceduresSH/T3523-19996.1.5SHJ520-92petrochemicalengineeringtechnicalspecificationforweldingofCR-MOheat-resistantsteelpipe6.1.6ofthepressurevesselNDT4730-946.2JBweldpreparation6.2.1constructionaccordingtothematerialsoftheprojectspecificationsandweldingmetho

56、ds,providingqualifiedweldingprocedurequalificationreport.6.2.2qualifiedweldingprocedurequalificationbasedonthepreparationofweldinginstruction,guidethewelderweldingoperations.6.2.3whereparticipationinsitewelding,mustbeinpossessionofboilerandpressurevesselweldercertificatesissuedbytheLaborDepartment.6

57、.2.4whereinvolvedinthepipeandsteelstructureweldingwelders,welderbeforeentryexaminationsshouldattendtheowners,andconstructionshouldbemadewithinthescopeandeligibilityapprovedbythequalityandtechnologysupervisiondepartmentsandowners.6.2.5qualifyforweldingwelder,weldingprocess,shouldbeapprovedbyweldingth

58、eweldingprocess.己-將坐標移至關找點主方向哪次羨轉再度后新生杼為二3 ： I cosfl -sin 3 | x，疝6 gs8 J yy)工旄幽像專桂區域內對奉個通及蛋求其梯度幄役和方向，蜷后對每個株 展幅小來以昌有楨貴舞敦，生蠅方尚擊者用.uergijj =匐匕叫± jx.j i)| exp - k : R更與美逢裊為列Q& K ;行感與關蜒忠的行照奉j 0 - if, b (i-</L )x(1 - )a -等于揩生子貿工式9, m力圖比龍EM 的一半:instrument has a single test condition, will be tr

59、ansferred to the coordination of the test phase, the instrument according to the standalone trials scheduled, with the process preparation of test solutions, equipped with professional technicians and skilled workers, to ensure safety and quality. 6. welding engineering construction programme 6.1 this engineering used construction specification 6.1.1 s