SIFT特征提取算法詳解

1、SIFT 特征提取算法詳解SIFT 特征提取算法總結(jié)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(guān)鍵點指定方向參數(shù)；5） 、關(guān)鍵點描述子的生成。民晨超司囪生班盡應(yīng)空問理論目的足帽 1 倒雅曙購多尺度和.髙斯藩積核星實 現(xiàn)尺毆換的唯的尺虞空簡定艾九丄二G（x,b申/（玄）其札 qj：b）宅尺賽可寒所趾鍛，匚（xy”7h 二 L0（y）壘至間生標芒量甌蟄標的大?t 枝定廚慷杓平涓也度，大尺 龐對.應(yīng)圖除旳慨把特杠小尺度對庖圖鮒細節(jié)樹 IL 大険葩應(yīng)粗 慢訂圧牴分稱干胚邑財應(yīng)胖細，灌佰汨 HD（斗帕a） =（G（xy掃r） -GCr.j; e）*

2、/（x,=列大;hr）-丄（乂壯J）L（x,y,（T）,（T = 1.6 a good tradeoff safety catch. Any production safety accide nt will cause an additi onal burde n on the county shouldbear joi nt and several liability, not worth the can dle. So en terprisesshould con scie ntiously assume the producti on safety of the main resp on

3、sibility for the safety producti on and the n catch producti on. All un its anddepartme nts resp on sible for safety producti on resp on sibility, as the main party leaders must in terve ne. Third, derelicti on of duty will pursue respon sibility. Stable now out of the questio n to responsibility an

4、daccountability is very strict. As far as possible to check the product ion isthe same, the first few days of the mainland occurred in product ion safetyaccide nts, the accide nt inv estigati on results also did not come out, thecounty Party Secretary, county magistrate, deputy magistrate and deputy

5、county magistrate all in situ removal, later also shall be investigated forcriminal responsibility. This is the derelict ion of duty shall be acco un table,we must attach great importa nee to. The fourth, preve nti on first, safety inproduct ion in place. Safety in product ion to preve nt the main,

6、less trouble,not afterwards to solve. Preve nti on is the key to impleme nt the safetyproduct ion resp on sibility system and the safety measures. The dan ger ofenterprises should take the initiative to pay close attention to the time to doprocedures, there is no legal complia nee procedures, once o

7、ut of troubleand regret. Unannoun ced visits to en terprises to actively take the initiativeto seize the time to formalities. In important holidays to in crease publicityand educati onD(x,y,(T),(T = 1.6 a good tradeoffsafety catch. Any product ion safety accide nt will cause an additi onal burde n o

8、n thecounty should bear joint and several liability, not worth the can dle. So en terprisesshould con scie ntiously assume the product ion safety of the main resp on sibility for thesafety producti on and the n catch product ion. All un its and departme nts resp on siblefor safety product ion resp o

9、n sibility, as the main party leaders must in terve ne. Third,derelicti on of duty will pursue resp on sibility. Stable now out of the question toresponsibility and accountability is very strict. As far as possible to check the product ionis the same, the first few days of the mai nla nd occurred in

10、 product ion safety accide nts,the accide nt inv estigatio n results also did not come out, the county Party Secretary,county magistrate, deputy magistrate and deputy county magistrate all in situ removal,later also shall be inv estigated for criminal responsibility. This is the dereliction of dutys

11、hall be accountable, we must attach great importance to. The fourth, prevention first,safety in production in place. Safety in production to prevent the main, less trouble, notafterwards to solve. Prevention is the key to implement the safety productionresponsibility system and the safety measures.

12、The danger of enterprises should takethe initiative to pay close attention to the time to do procedures, there is no legalcompliance procedures, once out of trouble and regret. Unannounced visits toenterprises to actively take the initiative to seize the time to formalities. In importantholidays to

13、increase publicity and education關(guān)于尺度空間的理解說明 :圖中的 2 是必須的，尺度空間是連續(xù)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(shù)量。尺度越大圖 像越模糊。next octave 是由 first octave降采樣得到（如 2）2（6kaFb、kLb）疋=2%尺度空間的所有取值，s 為每組層數(shù)，一般為 35在 DOG 尺度空間下的極值點詞了目杭

14、尺夷仝可前社值 矢一亍丹豐 點賈和已即有罰科鄒盧tt就.科禾否tt 它的圖tub麻昭的相邨點大站卡* 如圖， 中阿的伽 I 點利百同尺跆 8 彳相幫 并二 F 憎紹弋夏對應(yīng)戰(zhàn) A 2 勺去 26 個 慮出見以為探在尺慣空聞和二 IMB 糠空 闔都桂刑到想塩叮累一十點隹 00 職 ITxK1上匡 15i 上 F 兩匕勿 2 呂二訓協(xié)中.M 星大或晨滬擅時*戴認腳諫點是 B9 麋吐謨 尺贋下的一竹惟療。同一組中的相鄰尺度（由于 k 的取值關(guān)系，肯定是上下層）之間進行尋找safety catch. Any product ion safety accide nt will cause an addi

15、ti onal burde n on thecounty should bear joint and several liability, not worth the can dle. So en terprisesshould con scie ntiously assume the product ion safety of the mai n resp on sibility for thesafety producti on and the n catch production. All units and departments responsible forsafety produ

16、ction responsibility, as the main party leaders must intervene. Third,dereliction of duty will pursue responsibility. Stable now out of the question toresponsibility and accountability is very strict. As far as possible to check the productionis the same, the first few days of the mainland occurred

17、in production safety accidents,the accident investigation results also did not come out, the county Party Secretary,county magistrate, deputy magistrate and deputy county magistrate all in situ removal,later also shall be investigated for criminal responsibility. This is the dereliction of dutyshall

18、 be accountable, we must attach great importance to. The fourth, prevention first,safety in production in place. Safety in production to prevent the main, less trouble, notafterwards to solve. Prevention is the key to implement the safety productionresponsibility system and the safety measures. The

19、danger of enterprises should takethe initiative to pay close attention to the time to do procedures, there is no legalcompliance procedures, once out of trouble and regret. Unannounced visits toenterprises to actively take the initiative to seize the time to formalities. In importantholidays to incr

20、ease publicity and education在極值比較的過程中，每一組圖像的首末兩層是無法進行極值比較的，為了滿足尺度變化的連續(xù)性，我們在每一組圖像的頂層繼續(xù)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（金字塔每組有 S+2 層圖像.safety catch. Any product ion safety accide nt will cause an additi onalburde n on the county should bear joint and several liability, not worth the candle. So en ter

21、prises should con scie ntiously assume the product ion safety ofthe main resp on sibility for the safety producti on and the n catch product ion.All un its and departme nts resp on sible for safety product ion resp on sibility, asthe main party leaders must in terve ne. Third, derelicti on of duty w

22、ill pursueresp on sibility. Stable now out of the question to responsibility andaccountability is very strict. As far as possible to check the production is thesame, the first few days of the mainland occurred in production safety accidents,the accident investigation results also did not come out, t

23、he county PartySecretary, county magistrate, deputy magistrate and deputy county magistrateall in situ removal, later also shall be investigated for criminal responsibility. Thisis the dereliction of duty shall be accountable, we must attach great importanceto. The fourth, prevention first, safety i

24、n production in place. Safety in productionto prevent the main, less trouble, not afterwards to solve. Prevention is the keyto implement the safety production responsibility system and the safetymeasures. The danger of enterprises should take the initiative to pay closeattention to the time to do pr

25、ocedures, there is no legal compliance procedures,once out of trouble and regret. Unannounced visits to enterprises to activelytake the initiative to seize the time to formalities. In important holidays toincrease publicity and education畫也嫦三維二撫駐翹誦舉嗝尼戈憶引論 護譏耳込申吐俶判碾 j- 同呼播低對比度的關(guān)檯點和不憶疋晌邊殲自應(yīng)翩囲為 Dfl 磚干合產(chǎn)

26、空 菽電的邊竦響應(yīng) L 以增過匹配蹴也梶閒制 0 能力.空間尺度雖鞭“ rw J QL丁護門D(x :, oxJlx. l； - rDI V j. ir -K2 &t若冋用沁吐詡特征點就保留下未否則丟笨園邊縛咱應(yīng)的工除.一令定義不好的荷越荃今耳前祛他心植:畀辻綠甜 地方有較大前主匚常而在塞直邊垛的為曲有較小主曲翟主曲率 1 過_不 2M2曲 Hessi 歯矩豐HTT+言敵卻崇樣頂坤押苣估匸皋創(chuàng)，的主曲平利 H 的持征磁正比.母勸*犬琴征直 F 為章芬的將狂匱 則L P| H = w4 / 人=-+ bt-r iH 討站 $ I勺a-陽、則；TtHp I I + f尸川4.瀘MillI

27、Ji J (葉 1)2/(r), throw it out (SIFT uses r=10)表示 DOG 金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(shù)以精確確定關(guān)鍵點的位置和尺度(達到亞像素精度),safety catch. Any product ion safety accide nt will cause an additi onal burde n onthe county should bear joint and several liability, not worth the can dle. So en terprisesshould con scie ntio

28、usly assume the product ion safety of the main resp on sibility forthe safety producti on and the n catch product ion. All un its and departme nts resp onsible for safety product ion resp on sibility, as the main party leaders must in terve ne.Third, derelicti on of duty will pursue resp on sibility

29、. Stable now out of the question toresponsibility and accountability is very strict. As far as possible to check the production is the same, the first few days of the mai nla nd occurred in product ion safety accidents, the accide nt inv estigatio n results also did not come out, the county PartySec

30、retary, county magistrate, deputy magistrate and deputy county magistrate all insitu removal, later also shall be inv estigated for criminal responsibility. This is thedereliction of duty shall be acco un table, we must attach great importa nee to. Thefourth, preve nti on first, safety in producti o

31、n in place. Safety in producti on to preve ntthe main, less trouble, not afterwards to solve. Prevention is the key to impleme nt thesafety product ion resp on sibility system and the safety measures. The dan ger of enterprises should take the in itiative to pay close attention to the time to do pro

32、cedures,there is no legal complia nee procedures, once out of trouble and regret. Unannoun cedvisits to en terprises to actively take the in itiative to seize the time to formalities. Inimporta nt holidays to in crease publicity and educatio n苛每不關(guān)鋰貞相定方同參魏劃聞芒犍點鄰域像素前佛度方冋分布掙時每平樹點指定方問物 橈畀子具備如不變性Eg,*/亦+3

33、 - M -1 劇4 山上亠打- hiJjjff. 11-ir.1, I 11 j I3- .(3-14 in式中欺！+圈特戛的櫻值跖卉同公賞冥甲 L 浙用吋尺度為轉(zhuǎn)小關(guān)觀 點各自所在的尺專至比戲的關(guān)犍點己桂 I#洗畢.每卒關(guān)捷點宥三牛信臥怪亂? I -：4 由比罰以確宇一特征區(qū)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Identify peak and assign orientation and sum of magnitude to key poi ntThe user may choose a threshold to exclude key points

34、based on theirassig ned sum of magn itudes.利用關(guān)鍵點鄰域像素的梯度方向分布特性為每個關(guān)鍵點指定方向參數(shù)，使算子具備旋轉(zhuǎn)不變性。以關(guān)鍵點為中心的鄰域窗口內(nèi)采樣，并用直方圖統(tǒng)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(lǐng)域其對直方圖的貢獻也響應(yīng)減小丄 owe 論文中還提到要使用高斯函數(shù)對直方圖進行平滑，減少突變的影響safety catch. Any product ion safety accide nt will cause an additi onal burde n ont

35、he county should bear joint and several liability, not worth the can dle. So en terprisesshould con scie ntiously assume the production safety of the main responsibility for thesafety production and then catch production. All units and departments responsible forsafety production responsibility, as

36、the main party leaders must intervene. Third,dereliction of duty will pursue responsibility. Stable now out of the question toresponsibility and accountability is very strict. As far as possible to check the productionis the same, the first few days of the mainland occurred in production safety acci

37、dents,the accident investigation results also did not come out, the county Party Secretary,county magistrate, deputy magistrate and deputy county magistrate all in situ removal,later also shall be investigated for criminal responsibility. This is the dereliction of dutyshall be accountable, we must

38、attach great importance to. The fourth, prevention first,safety in production in place. Safety in production to prevent the main, less trouble, notafterwards to solve. Prevention is the key to implement the safety productionresponsibility system and the safety measures. The danger of enterprises sho

39、uld takethe initiative to pay close attention to the time to do procedures, there is no legalcompliance procedures, once out of trouble and regret. Unannounced visits toenterprises to actively take the initiative to seize the time to formalities. In importantholidays to increase publicity and educat

40、ion關(guān)鍵點描述子的生成步驟將坐標軸璇轉(zhuǎn)為關(guān)鍵點的方向，創(chuàng)確 保旄轉(zhuǎn)不變性生成描述子對于一個關(guān)錐責產(chǎn)生佗8個數(shù)據(jù)，卽量婆形或化8維的SIFT埒征直臺歸一化潯特征向量的孫度歸一比.則可氐進h處理.一步去除光照變化旳影響*通過對關(guān)鍵點周圍圖像區(qū)域分塊，計算塊內(nèi)梯度直方圖，生成具有獨特性的向量，這個向量是該區(qū)域圖像信息的一種抽象，具有唯一性。首先將峑標軸旄轉(zhuǎn)対關(guān)讎點的方問.也弭保坤不覺阻 以特征盤竟中霸 B瞞鄰軸為第福鬲門.將采科煦與持咸的鹹方馳 過曲恤站掃入豈含酋個育向直方圖.最后獲得 2*2 媯越特征 巻熾子”和圖如下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，箭頭方向代表了像素梯度方

41、向，箭頭長度代表該像素的幅值。然后在 4X4的窗口內(nèi)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safety catch. Any production safety accident will cause an additional burden on thecounty should bear joint and several liability, not worth the candle. So enterprisesshould conscientiously assume the production safety of the main respon

42、sibility for thesafety production and then catch production. All units and departments responsible forsafety production responsibility, as the main party leaders must intervene. Third,dereliction of duty will pursue responsibility. Stable now out of the question toresponsibility and accountability i

43、s very strict. As far as possible to check the productionis the same, the first few days of the mainland occurred in production safety accidents,the accident investigation results also did not come out, the county Party Secretary,county magistrate, deputy magistrate and deputy county magistrate all

44、in situ removal,later also shall be investigated for criminal responsibility. This is the dereliction of dutyshall be accountable, we must attach great importance to. The fourth, prevention first,safety in production in place. Safety in production to prevent the main, less trouble, notafterwards to

45、solve. Prevention is the key to implement the safety productionresponsibility system and the safety measures. The danger of enterprises should takethe initiative to pay close attention to the time to do procedures, there is no legalcompliance procedures, once out of trouble and regret. Unannounced v

46、isits toenterprises to actively take the initiative to seize the time to formalities. In importantholidays to increase publicity and education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(guān)鍵點附近的四 個直方圖數(shù)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(zhuǎn)為主方向safety catch

47、. Any production safety accident will cause an additional burden on thecounty should bear joint and several liability, not worth the candle. So enterprisesshould conscientiously assume the production safety of the main responsibility for thesafety production and then catch production. All units and

48、departments responsible forsafety production responsibility, as the main party leaders must intervene. Third,dereliction of duty will pursue responsibility. Stable now out of the question toresponsibility and accountability is very strict. As far as possible to check the productionis the same, the f

49、irst few days of the mainland occurred in production safety accidents,the accident investigation results also did not come out, the county Party Secretary,county magistrate, deputy magistrate and deputy county magistrate all in situ removal,later also shall be investigated for criminal responsibilit

50、y. This is the dereliction of dutyshall be accountable, we must attach great importance to. The fourth, prevention first,safety in production in place. Safety in production to prevent the main, less trouble, notafterwards to solve. Prevention is the key to implement the safety productionresponsibili

51、ty system and the safety measures. The danger of enterprises should takethe initiative to pay close attention to the time to do procedures, there is no legalcompliance procedures, once out of trouble and regret. Unannounced visits toenterprises to actively take the initiative to seize the time to fo

52、rmalities. In importantholidays to increase publicity and education1.勸之計乍船軌十所常的圈像這域器it#揮康方曲扛方圖由關(guān)蜀點商在JUt的摸禰因像計丼戶生.圏借區(qū)爲前半輕連it下晁計界：皿- -盅縣實臺養(yǎng)呀在組（xZ）的組內(nèi)甩上d = 4safety catch. Any product ion safety accide nt will cause an additi onal burde n onthe county should bear joint and several liability, not worth t

53、he can dle. So en terprisesshould con scie ntiously assume the product ion safety of the main resp on sibility forthe safety producti on and the n catch product ion. All un its and departme nts resp onsible for safety product ion resp on sibility, as the main party leaders must in terve ne.Third, de

54、relicti on of duty will pursue resp on sibility. Stable now out of the question toresponsibility and accountability is very strict. As far as possible to check the productionis the same, the first few days of the mainland occurred in production safety accidents,the accident investigation results als

55、o did not come out, the county Party Secretary,county magistrate, deputy magistrate and deputy county magistrate all in situ removal,later also shall be investigated for criminal responsibility. This is the dereliction of dutyshall be accountable, we must attach great importance to. The fourth, prev

56、ention first,safety in production in place. Safety in production to prevent the main, less trouble, notafterwards to solve. Prevention is the key to implement the safety productionresponsibility system and the safety measures. The danger of enterprises should takethe initiative to pay close attentio

57、n to the time to do procedures, there is no legalcompliance procedures, once out of trouble and regret. Unannounced visits toenterprises to actively take the initiative to seize the time to formalities. In importantholidays to increase publicity and education己-將寶標務(wù)至關(guān)鍵點主方向那盤住轉(zhuǎn)甬鷹后新坐標為;在凹像F牡區(qū)蟻內(nèi)甘乖卜像A蠱並其

58、謀良幅惜和金倚，龍唇對命奪黒a:爭于謂 M 子貿(mào)口宣黃3b*左希圖卅弦 靑燦 制一斗:safety catch. Any product ion safety accide nt will cause an additionalburde n on the county should bear joint and several liability, not worth thecan dle. So en terprises should con scie ntiously assume the product ionsafety of the main resp on sibility fo

59、r the safety producti on and the n catchproduct ion. All un its and departme nts resp on sible for safety product ionresp on sibility, as the main party leaders must in terve ne. Third, dereliction of duty will pursue resp on sibility. Stable now out of the question toresponsibility and accountabili

60、ty is very strict. As far as possible to checkthe product ion is the same, the咸幅整索XI盛斷扳魚巖魏，生戌育詢笛專再uergijj =耳衛(wèi)打打，.仁廿卜exp -工:詼點與七譴點場蕪去石：JL:帝鷹勾芙比最的庁匝禹?first few days of the mai nla nd occurred in product ion safety accide nts,the accide nt inv estigatio n results also did not come out, the county PartySecr