數(shù)字圖像處理PPT(3)

1、Digital Image Processing第三章第三章灰度變換與空間濾波灰度變換與空間濾波Digital Image Processing3.13.1背景知識(shí)背景知識(shí)3.23.2基本灰度變換基本灰度變換3.33.3直方圖處理直方圖處理3.43.4空間濾波基礎(chǔ)空間濾波基礎(chǔ)3.53.5平滑空間濾波器平滑空間濾波器3.63.6銳化空間濾波器銳化空間濾波器3.73.7混合空間增強(qiáng)法混合空間增強(qiáng)法本章內(nèi)容本章內(nèi)容Digital Image Processing圖象增強(qiáng)的含義和目的圖象增強(qiáng)的含義和目的圖像增強(qiáng)是要突出圖像中的某些信息，同時(shí)削弱或去除圖像增強(qiáng)是要突出圖像中的某些信息，同時(shí)削弱或去除某些

2、不需要信息的一種處理方法，以得到對(duì)具體應(yīng)用來(lái)某些不需要信息的一種處理方法，以得到對(duì)具體應(yīng)用來(lái)說(shuō)說(shuō)視覺(jué)效果視覺(jué)效果更更“好好”，或更，或更“有用有用”的圖像的技術(shù)的圖像的技術(shù). .Digital Image Processing圖象增強(qiáng)的含義和目的圖象增強(qiáng)的含義和目的灰度均衡灰度均衡濾波增強(qiáng)濾波增強(qiáng)Digital Image Processing圖象增強(qiáng)的含義和目的圖象增強(qiáng)的含義和目的圖像在生成、傳輸或者處理過(guò)程中會(huì)引入噪聲或使圖像圖像在生成、傳輸或者處理過(guò)程中會(huì)引入噪聲或使圖像變模糊，從而降低了圖像質(zhì)量，甚至淹沒(méi)了特征，給分變模糊，從而降低了圖像質(zhì)量，甚至淹沒(méi)了特征，給分析帶來(lái)了困難。析帶來(lái)了

3、困難。 v 改善圖象的視覺(jué)效果，提高圖像的清晰度；改善圖象的視覺(jué)效果，提高圖像的清晰度；v 將圖象轉(zhuǎn)換成更適合于人眼觀察和將圖象轉(zhuǎn)換成更適合于人眼觀察和機(jī)器分析識(shí)別機(jī)器分析識(shí)別的形的形式，以便從圖象中獲取更有用的信息。式，以便從圖象中獲取更有用的信息。 Digital Image Processing空間域處理：空間域處理：點(diǎn)處理（圖象灰度變換、直方圖均衡等）；鄰域處理（線(xiàn)性、非線(xiàn)性平滑和銳化等）；頻域處理：頻域處理：高、低通濾波、同態(tài)濾波等 圖象增強(qiáng)的含義和目的圖象增強(qiáng)的含義和目的Manipulation of pixel values in the image plane2D DFTFre

4、quency filteringDigital Image Processing73.1 3.1 背景知識(shí)背景知識(shí)v圖像增強(qiáng)的分類(lèi)Digital Image Processingv空間域增強(qiáng)處理空間域增強(qiáng)處理( (Spatial-domain ProcessingSpatial-domain Processing )處理算子處理算子 T: Operator on f, defined over some neighbor of (x,y)(多為方形和矩形陣列，又稱(chēng)為空間濾波器)T operates only on (x,y).T operates on a small neighborhood

5、 of (x,y).83.1 3.1 背景知識(shí)背景知識(shí)yxfTyxg,Digital Image Processing93.1 Background3.1 Background r,s分別是f(x,y)和g(x,y)在點(diǎn)(x,y)的灰度級(jí)Processes pixels gray-level without considering spatial attributes.T: Gray-level (Intensity) transformation function ry, xfsy, xgTTContrast stretchingThresholding (Binarization)Digi

6、tal Image Processing103.1 Background3.1 BackgroundvExample: using PSDigital Image Processing113.1 Background3.1 Background(Spatial Filtering)(Spatial Filtering)g(i,j) depends not only on f(i,j) but also some neighborhood of (i,j)g(i,j) = T f(i,j) w where T is an operator defined over a pre-defined n

7、eighborhood of (i,j).Mask(掩模), Filter(濾波器), Kernel(核), Template(模板), Window(窗口)w Square, rectangle, or sometimes circular typeDigital Image Processing123.2 Basic Gray Level Transformations3.2 Basic Gray Level Transformationsv Implementation by Look-Up Table (LUT) ry, xfsy, xgTTrs025512542253：2541255

8、0Digital Image Processing133.2 Basic Gray Level Transformations3.2 Basic Gray Level TransformationsvImage Negatives(Image Negatives(圖像反轉(zhuǎn)圖像反轉(zhuǎn)) )Reverse the order of pixel intensity g(i,j) = 255 - f(i,j) or s = 255 - rEx: Displaying medical images.Digital Image Processing143.2 Basic Gray Level Transfo

9、rmations3.2 Basic Gray Level TransformationsvLog (or Inverse Log) Transformations (Log (or Inverse Log) Transformations (對(duì)數(shù)變換對(duì)數(shù)變換) )s = c log(1+r)c c是常數(shù)，是常數(shù)，r=0r=0有時(shí)原圖的動(dòng)態(tài)范圍太大，超出某些顯示設(shè)備的允許有時(shí)原圖的動(dòng)態(tài)范圍太大，超出某些顯示設(shè)備的允許動(dòng)態(tài)范圍，如果直接使用原圖，則一部分細(xì)節(jié)可能丟動(dòng)態(tài)范圍，如果直接使用原圖，則一部分細(xì)節(jié)可能丟失，解決辦法是對(duì)原圖進(jìn)行灰度壓縮，如對(duì)數(shù)變換失，解決辦法是對(duì)原圖進(jìn)行灰度壓縮，如對(duì)數(shù)變換D

10、igital Image Processing153.2 Basic Gray Level Transformations3.2 Basic Gray Level TransformationsvLog (or Inverse Log) Transformations (Log (or Inverse Log) Transformations (對(duì)數(shù)變換對(duì)數(shù)變換) )s = c log(1+r)Log Transform: Log Transform: expand the dark pixel values while compressing the higher-level values.

11、Inverse Log Transform:Inverse Log Transform: compress the dark pixel values while expanding the higher-level values. Ex: Displaying Fourier Spectrum原圖傅里葉頻域圖傅里葉頻域?qū)?shù)圖Digital Image Processing163.2 Basic Gray Level Transformation3.2 Basic Gray Level Transformationv Power-Law Transformations(Power-Law Tr

12、ansformations(冪次變換冪次變換) )When g1: compress the dark pixel values while expanding the higher-level values.ggrcscrsor Digital Image Processing173.2 Basic Gray Level Transformation3.2 Basic Gray Level Transformationv Gamma Correction(Gamma Correction(伽馬矯正伽馬矯正) )Most imaging devices (printers, scanners,

13、 monitors) respond according to a power law.Ex: CRT devices have an intensity-to-voltage response that is a power function, with exponents varying from approximately 1.8 to 2.5.Digital Image Processing183.2 Basic Gray Level Transformation3.2 Basic Gray Level Transformationv Power-Law Transformations

14、 (Power-Law Transformations (冪次變換冪次變換) )Ex1: Ex1: General-purpose Contrast ManipulationGeneral-purpose Contrast ManipulationMR image of Upper thoracic human spine人體胸上部脊椎骨折的核磁共振圖像g = 0.6g = 0.4g = 0.3When g1,bright image gets darker(降低灰度級(jí)，使圖像變暗)航拍圖矯正Digital Image Processing203.2 Basic Gray Level Tran

15、sformation3.2 Basic Gray Level TransformationvContrast Stretching(Contrast Stretching(對(duì)比度拉伸對(duì)比度拉伸) )When the range of pixel values in an image is smaller than the dynamic range of the display device, Increase the dynamic range of the gray levels in the image, while preserving the order of gray levels

16、. s = T(r): Single-valued and monotonically increasingDigital Image Processing213.2 Basic Gray Level Transformation3.2 Basic Gray Level TransformationvContrast Stretching cont.Contrast Stretching cont.Piecewise-LinearTransformation(分段分段線(xiàn)線(xiàn)性性變換變換)Digital Image Processing223.2 Basic Gray Level Transfor

17、mation3.2 Basic Gray Level Transformationv Gray-level SlicingGray-level SlicingHighlight a specific range of gray levels in an image.Either preserves the background or produces a binary image.Digital Image Processing233.2 Basic Gray Level Transformation3.2 Basic Gray Level Transformationv Bit-Plane

18、Slicing(Bit-Plane Slicing(位平面切片位平面切片) )假設(shè)圖像中每個(gè)像素的灰度級(jí)是256，這可以用8位來(lái)表示，假設(shè)圖像是由8個(gè)1位的平面組成，范圍從位平面0到位平面7。其中，位平面0包含圖像中像素的最低位，位平面7包含像素的最高位。作用w 通過(guò)對(duì)特定位提高亮度，改善圖像質(zhì)量w 較高位包含大多數(shù)視覺(jué)重要數(shù)據(jù)w 較低位包含圖像中微小細(xì)節(jié)數(shù)據(jù)w 分解為位平面，可以分析每一位在圖像中的相對(duì)重要性 Digital Image Processing243.2 Basic Gray Level Transformation3.2 Basic Gray Level Transforma

19、tionvBit-Plane Slicing cont.Bit-Plane Slicing cont.1286432168421Digital Image Processing253.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )v HistogramHistogram provides a of the appearance of an image.直方圖是一種二維統(tǒng)計(jì)圖表，它的兩個(gè)坐標(biāo)分別是統(tǒng)計(jì)樣本(灰度級(jí))和該樣本對(duì)應(yīng)的某個(gè)屬性(個(gè)數(shù))的度量。Normalized(規(guī)范化) histogram 可將 視作概率密度

20、函數(shù) nnLrnrhLkkkkk1110 and where function Discrete 111Lkkkkrpnnrp andpDigital Image Processing263.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )v HistogramHistogram Equalization (or Linearization)(Equalization (or Linearization)(直方圖均衡化直方圖均衡化) ) 直方圖均衡直方圖均衡化是圖像處理領(lǐng)域中利用圖像直方圖對(duì)對(duì)比度進(jìn)行化是圖像處理領(lǐng)域中利

21、用圖像直方圖對(duì)對(duì)比度進(jìn)行調(diào)整的方法。調(diào)整的方法。 我們我們的目標(biāo)是將原始圖像的目標(biāo)是將原始圖像A(A(x,yx,y) )每一像素點(diǎn)的像素級(jí)每一像素點(diǎn)的像素級(jí)r r 變成一個(gè)變成一個(gè)新的圖像新的圖像B(B(x,yx,y) )上對(duì)應(yīng)像素點(diǎn)的新的像素級(jí)上對(duì)應(yīng)像素點(diǎn)的新的像素級(jí)s s。這樣我們就需要一個(gè)變換 s=T(r)。r : normalized gray level (0 r 1) with r = 0 (black) and r = 1 (white).s = T(r) : single-valued and monotonically increasing.0 s = T(r) 1 for

22、0 r 1Then, r = T-1(s) (0 s 1) is also single-valued and monotonically increasing. pr(r), ps(s) - probability density functions of r and s, respectively. Digital Image Processing273.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )v HistogramHistogram Equalization (or Linearization)(Equal

23、ization (or Linearization)(直方圖均衡化直方圖均衡化) )如何求如何求T(r)T(r)呢？呢？首先我們假設(shè)圖像是連續(xù)的，首先我們假設(shè)圖像是連續(xù)的， 可以看作是隨可以看作是隨機(jī)變量為機(jī)變量為 r r 的概率密度函數(shù)，原始圖像在灰度級(jí)區(qū)間的概率密度函數(shù)，原始圖像在灰度級(jí)區(qū)間 上的像素個(gè)數(shù)為上的像素個(gè)數(shù)為 , , 經(jīng)過(guò)變換使得原來(lái)的區(qū)間經(jīng)過(guò)變換使得原來(lái)的區(qū)間 變變?yōu)樾聢D像的區(qū)間為新圖像的區(qū)間 ，但是總的像素個(gè)數(shù)沒(méi)有改變。變換后但是總的像素個(gè)數(shù)沒(méi)有改變。變換后區(qū)間區(qū)間 上的像素個(gè)數(shù)為上的像素個(gè)數(shù)為 , , 那么有那么有( )rpr ,r rdr( )rpr dr ,r rdr

24、 ,s sds( )sp s ds ,s sds( )( )srp s dspr dr(1)Digital Image Processing283.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )v HistogramHistogram Equalization (or Linearization)(Equalization (or Linearization)(直方圖均衡化直方圖均衡化) )理想化的直方圖均衡，是使輸出圖像直方圖每一像素級(jí)的像素點(diǎn)個(gè)理想化的直方圖均衡，是使輸出圖像直方圖每一像素級(jí)的像素點(diǎn)個(gè)數(shù)都為同一常數(shù)

25、數(shù)都為同一常數(shù)c c, ,也就是也就是 , , 根據(jù)式根據(jù)式(1)(1)，我們有，我們有令令C=1C=1，則有，則有 很顯然很顯然000( )( )ssrsrp s dscdspr dr( )sp sc0( )rrspr dr0( )( )rrT rpr drDigital Image Processing293.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogram EqualizationHistogram Equalization i.e., T is the cumulative distribut

26、ion functioncumulative distribution function of pr(r) ps(s) is a uniformuniform density independent of pr(r).Histogram equalization increases the dynamic rangedynamic range of the pixels. 0 01rrrdssT rpr drrprdr 1 01rsrrprdrpsprsdsprLetDigital Image Processing303.3 Histogram Processing(3.3 Histogram

27、 Processing(直方圖處理直方圖處理) )vHistogram Equalization cont.Histogram Equalization cont.For discrete values 11000L, ,knnrprTskjjkjjrkkDigital Image Processing313.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogram Equalization Histogram Equalization ExampleExampleSuppose a 3-bit image

28、(L=8) of 64x64 pixels, the intensity distribution is shown in table belowr0=07900.19r1=110230.25r2=28500.21r3=36560.16r4=43290.08r5=52450.06r6=61220.03r7=7810.02rkkprnMNkrkn 0000007 71.33rjjjjsTrprnn 1110107 73.08rjjjjsTrprnn24.55s35.67s46.23s56.65s66.86s77.00sDigital Image Processing323.3 Histogram

29、 Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogram Equalization Histogram Equalization ExampleExampleRound the to the nearest integer:01.331s13.083s24.555s35.676s46.236s56.657s66.867s77.007s0sDigital Image Processing333.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogra

30、m Equalization Histogram Equalization ExampleExample原原圖圖經(jīng)經(jīng)均衡化的均衡化的圖圖Digital Image Processing343.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogram Matching (SpecificationHistogram Matching (Specification- -直方圖規(guī)定化直方圖規(guī)定化) )直方圖匹配又叫直方圖規(guī)定化（Histogram Normalization/Matching）是指對(duì)一副圖像進(jìn)行變換

31、，使其直方圖與另一幅圖像的直方圖或特定函數(shù)形式的直方圖進(jìn)行匹配。Digital Image Processing353.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogram Matching (SpecificationHistogram Matching (Specification- -直方圖規(guī)定化直方圖規(guī)定化) )pr(r)w probability density function of the original imagepz(z)w desired probability density fu

32、nction (PDF)Procedure:w Histogram equalizing the original image :w Histogram equalizing the desired PDF : w Note that ps(s) = pv(v) as a uniform distribution : rrdwwprTs0 zzdwwpzGv0 rTGsGvGz111Digital Image Processing363.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vHistogram Matchin

33、g (Specification) cont.Histogram Matching (Specification) cont.Digital Image Processing373.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )Global enhancementDigital Image Processing383.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )v Local EnhancementLocal Enhancement（局部增強(qiáng)

34、）（局部增強(qiáng)）To enhance details over small areas.Based on the gray-level distribution in the neighborhood of every pixel.Local histogram equalizationLocal histogram equalizationw Define an n x m neighborhood as a local area.w Perform histogram equalization (or specification) over the local area.w Move the

35、 center of n x m region to the adjacent pixel, and continue.Digital Image Processing393.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vUse of Histogram StatisticsUse of Histogram Statistics（直方圖統(tǒng)計(jì)學(xué)的使用）（直方圖統(tǒng)計(jì)學(xué)的使用）Mean BrightnessVariance ContrastLet Sxy denote a neighborhood of specified

36、 size, centered at (x,y). GLiiiGLiiiLiiiDrpmrMnnrrprm1021010 :deviation standard Global :mean GlobalxyxyxyxyxySt , st , sSt , sSSt , st , st , sSrpmrrprm22 : varianceLocal :mean LocalDigital Image Processing403.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vExamplenumbers Magic : wher

37、eotherwise AND if210210k,k,k ,Ey, xfDkDkMkmy, xfEy, xgGSGGSxyxyDigital Image Processing413.3 Histogram Processing(3.3 Histogram Processing(直方圖處理直方圖處理) )vExample cont.Digital Image Processing423.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic OperationsArithmetic/Logic OperationsPixel-by-p

38、ixel operations between two or multiple imagesvImage SubtractionImage Subtraction（圖像減法）（圖像減法）O(i,j) = |I1(i,j) - I2(i,j)|To detect movement (or difference) of an object between two images acquired at different times.Satellite reconnaissance, Moving object detection, Mask-mode radiography.Digital Ima

39、ge Processing43ExampleExampleDigital Image Processing44ExampleExampleDigital Image Processing453.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic OperationsArithmetic/Logic Operationsv Image Averaging Image Averaging （圖像平均處理）（圖像平均處理）Observed imageg(i,j) = f(i,j) + (i,j)where f(i,j) : origi

40、nal image,(i,j) : noise which is uncorrelated and has zero mean at any (i,j).Suppose there is a set of noisy images gk(i,j) which hasAs M increases, mg(i,j) will approach to f(i,j) and the variability of the pixel values decrease.This operation reduces time-varying random noisetime-varying random no

41、ise in an image.jifjimEjigMjimgMkkg,11jijimjijimMMgg,1122Digital Image Processing463.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic OperationsArithmetic/Logic OperationsvEx: AveragingDigital Image Processing473.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic OperationsArithmet

42、ic/Logic OperationsvAND/OR OperationsMaskingorRegion of Interest (ROI)Digital Image Processing483.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic Operations Arithmetic/Logic Operations vImage Combination OperationImage Combination OperationMix similar images from the same scene to create

43、a resulting image that better conveys some attributes of the image.vImage Compositing OperationImage Compositing OperationMix unrelated images, or portions of images, to create an entirely new scene (Image mask)vDual image Combination FunctionDual image Combination FunctionO(i,j) = I1(i,j) # I2(i,j)

44、 where # is one of operations among +, -, AND, OR, XOR, etc.Digital Image Processing493.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic Operations Arithmetic/Logic Operations 英科學(xué)家繪制全球英科學(xué)家繪制全球4141個(gè)國(guó)家女性個(gè)國(guó)家女性“平均臉平均臉”【環(huán)球網(wǎng)報(bào)道 記者 譚利婭】 全球不同地區(qū)人的相貌各有差異，而同一地區(qū)則又有共同指出。收集全球41個(gè)國(guó)家或地區(qū)數(shù)千張女士照片，通過(guò)計(jì)算機(jī)程序?qū)⒚繌堈掌?/p>

45、疊，最終繪制出各國(guó)女性的“平均相貌”。據(jù)英國(guó)每日郵報(bào)9月29日?qǐng)?bào)道，此次實(shí)驗(yàn)采用了19世紀(jì)80年代人類(lèi)學(xué)家高爾頓首創(chuàng)的“合成肖像法”，將多張肖像重疊得出一個(gè)“平均相貌”。研究者以參與實(shí)驗(yàn)者的眼睛為重點(diǎn)，分析其外表吸引力。分析稱(chēng)，此次實(shí)驗(yàn)沒(méi)有采用大量輪廓不清的照片，只是在重疊照片前，用計(jì)算機(jī)簡(jiǎn)單調(diào)整了各人的五官形狀；大部分國(guó)家女士頭發(fā)呈深啡色，這是因?yàn)樵谡掌丿B過(guò)程中，金發(fā)易被深色頭發(fā)淡化。不過(guò)，研究者繪制的結(jié)果圖顯示大部分女性均有無(wú)瑕肌膚和大眼睛，看起來(lái)全是20歲出頭的年輕模樣，因此這項(xiàng)研究也被指脫離現(xiàn)實(shí)。Digital Image Processing503.4 Enhancement Us

46、ing 3.4 Enhancement Using Arithmetic/Logic Operations Arithmetic/Logic Operations Digital Image Processing513.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic Operations Arithmetic/Logic Operations Digital Image Processing523.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic Opera

47、tions Arithmetic/Logic Operations Digital Image Processing533.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic Operations Arithmetic/Logic Operations Digital Image Processing543.4 Enhancement Using 3.4 Enhancement Using Arithmetic/Logic OperationsArithmetic/Logic Operationsv Adjustment of

48、Dynamic RangeResults of pixel-by-pixel operation may overflow or underflow.Ex: 1 byte/pixel 0 O(x,y) 2551.Saturation (or Clipping)2.Fixed Addition and Division3.Adaptive Shifting and Scaling (Linear Scaling) line stepDigital Image Processing683.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filt

49、ers（銳化空間濾波器）（銳化空間濾波器）v2D LaplacianLaplacian（拉普拉斯算子）（拉普拉斯算子）LinearIsotropic（各向同性）:w Rotation-invariant Homogeneous regions become dark.y, xfy, xfy, xfy,xfy,xffy, xfy, xfy, xfyfy,xfy, xfy,xfxfyfxff41111121121222222222201mniiw該算子可用如下之掩該算子可用如下之掩模實(shí)現(xiàn)模實(shí)現(xiàn)Digital Image ProcessingvLaplacian for image enhancem

50、ent拉氏濾波強(qiáng)調(diào)突變及降低灰度慢變區(qū)將拉氏濾波圖疊加到原圖可以在強(qiáng)調(diào)銳化效果的同時(shí)恢復(fù)原背景信息，變換公式如下：693.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）00000022,wy, xfy, xf,wy, xfy, xfy, xg if ifw(0,0): 拉普拉斯算子的中心系數(shù)拉普拉斯算子的中心系數(shù)Digital Image ProcessingvLaplacian for image enhancement示例703.7 Sharpening Spatial Filters

51、3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）Digital Image ProcessingvLaplacian for image enhancement示例，4鄰域拉氏濾波結(jié)果713.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）Digital Image ProcessingvLaplacian for image enhancement示例，8鄰域拉氏濾波結(jié)果723.7 Sharpening Spatial Filters3.7

52、Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）Digital Image Processing733.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）vLaplacian for image enhancement111152y, xfy, xfy,xfy,xfy, xfy, xfy, xfy, xg上例中的實(shí)現(xiàn)是通過(guò)原圖上例中的實(shí)現(xiàn)是通過(guò)原圖減去拉氏變換得到的，實(shí)減去拉氏變換得到的，實(shí)際中可以通過(guò)如上的變換際中可以通過(guò)如上的變換一次完成一次完成Di

53、gital Image Processing743.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）vUnsharpUnsharp masking and High-boost filtering masking and High-boost filtering（反銳化掩（反銳化掩蔽與高提升濾波處理）蔽與高提升濾波處理）Unsharp masking: 長(zhǎng)期以來(lái)在出版業(yè)中使用的圖像銳化是將圖像模糊形式從原始圖像中去除.通過(guò)反銳化掩蔽來(lái)完成. 反銳化掩蔽的基本算法如下: 是通過(guò)人為方法得到的模

54、糊圖像（平滑濾波），c是常數(shù)。 會(huì)使原圖的低頻成分損失很多,而高頻成分較完整地被保留下。（細(xì)節(jié)部分占據(jù)高頻部分，背景部分占據(jù)低頻部分）,sfx yfx yc fx yfx y,fx y,fx yfx y反反銳銳化掩蔽化掩蔽Digital Image ProcessingvUnsharpUnsharp masking and High-boost filtering masking and High-boost filtering（反銳化掩（反銳化掩蔽與高提升濾波處理）蔽與高提升濾波處理）Unsharp masking: 可以前述簡(jiǎn)單局部平均法求得,鄰域取3x3,掩模為：令c=9，則 的掩模為7

55、53.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）,sfx y,fx y1-1 -1 -10000001 1 1-19-1010090 - 1 1 1-1 -1 -10000001 1 1 WDigital Image ProcessingvUnsharpUnsharp masking and High-boost filtering masking and High-boost filtering（反銳化掩（反銳化掩蔽與高提升濾波處理）蔽與高提升濾波處理）Unsharp masking: 763.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）（a a）原圖像）原圖像 （b b）被模糊的圖像）被模糊的圖像（c c）用（）用（b b）反銳化（）反銳化（a a）所得的圖像）所得的圖像Digital Image Processing773.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters（銳化空間濾波器）（銳化空間濾波器）vUnsharpUnshar