chapter 3 image enhancement in the spatial domaincsie/ycliaw/dip/03_enhancement.pdf · © 2002 r....
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
The principal objective of enhancementThe principal objective of enhancementto process an image so that the result is more suitablethan the original image for a specific application.
Enhancement methodsEnhancement methodsSpatial Domain (in this chapter)
based on direct manipulation of pixels in an image
Frequency Domain (in chapter 4)based on modifying the Fourier transform of an image
The viewer is the ultimate judge of how well ofThe viewer is the ultimate judge of how well ofa particular method works.a particular method works.
Chapter 3 Chapter 3 Image Enhancement in theImage Enhancement in theSpatial DomainSpatial Domain
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Chapter 3 Chapter 3 Image Enhancement in theImage Enhancement in theSpatial DomainSpatial Domain
3.1 Background3.2 Some basic gray level transformations3.3 Histogram processing3.4 Enhancement using arithmetic/logic operations3.5 Basics of spatial filtering3.6 Smoothing spatial filters3.7 Sharpening spatial filters3.8 Combining spatial enhancement methods
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.1 Background3.1 Background
Spatial domain methods operate directly onSpatial domain methods operate directly onimage pixelsimage pixels
T operates only for one pixel
MappingContrast StretchingThresholdingBinary Image
2)-(3.1 )(rTs =
( ) ( )[ ] 1)-(3.1 ,, yxfTyxg =
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.1 Background3.1 Background
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
– T operates with neighboring pixels• Mask (filter, kernel, template, window)
3.1 Background3.1 Background
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
( )[ ] ( ) ( ) ( )( ) ( ) ( )( ) ( ) ( ) 222120
121110
020100
1,1,11,11,,1,
1,1,11,1,
myxfmyxfmyxfmyxfmyxfmyxf
myxfmyxfmyxfyxfT
×+++×++×−++×++×+×−
+×+−+×−+×−−=
=
222120
121110
020100
mmmmmmmmm
Mask
3.1 Background3.1 Background
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.1 Background3.1 Background
=
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Mask
Original Image Processed Image
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformations
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsImage NegativeImage Negative
( ) 1)-(3.2 1 rLs −−=
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformations
Original Image Processed Image
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsLog TransformationLog Transformation
( ) 2)-(3.2 1log rcs +=
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsLog TransformationLog Transformation
Original Image Processed Image
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPower-Law TransformationPower-Law Transformation
3)-(3.2 γcrs =
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPower-Law TransformationPower-Law Transformation
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPower-Law TransformationPower-Law Transformation
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPower-Law TransformationPower-Law Transformation
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPiecewise-Linear Transformation FunctionsPiecewise-Linear Transformation Functions
Contrast StretchingContrast Stretching
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPiecewise-Linear Transformation FunctionsPiecewise-Linear Transformation Functions
Processed ImageOriginal Image
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPiecewise-Linear Transformation FunctionsPiecewise-Linear Transformation Functions
Gray-level slicingGray-level slicing
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Processed ImageOriginal Image
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPiecewise-Linear Transformation FunctionsPiecewise-Linear Transformation Functions
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPiecewise-Linear Transformation FunctionsPiecewise-Linear Transformation Functions
Bit-plane slicingBit-plane slicing
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.2 3.2 Some basic gray level transformationsSome basic gray level transformationsPiecewise-Linear Transformation FunctionsPiecewise-Linear Transformation Functions
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram Processing
( ) kk nrh =
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram Processing
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram EqualizationHistogram Equalization
Transformation FunctionTransformation Function
Inverse functionInverse function
( ) 1)-(3.3 1r0 ≤≤= rTsConditions:(a) T(r) is single valued and
monotonically increasing(b) 0 ≤ T(r) ≤ 1 for 0 ≤ r ≤ 1
( ) 2)-(3.3 1s0 1 ≤≤= − sTr
*不一定符合條件(a)或(b)
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram EqualizationHistogram Equalization
PDFsPDFs((機率密度函式機率密度函式) ) of of rr and and ss
( )rpr
( ) ( ) 3)-(3.3 dsdrrpsp rs =s的機率密度函式:
r的機率密度函式:
s的機率密度函式為所有經3.3-1公式轉換後會對映到s值之所有r值之機率密度函式的總和
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram EqualizationHistogram Equalization
If s is the Cumulative Density Function (CDF) of pr
*符合條件(a)與(b)
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
( ) ( )dsdrrpsp rs =
3.3 Histogram Processing3.3 Histogram ProcessingHistogram EqualizationHistogram Equalization
ps(s) is a uniform PDFBecause ps(s) is 1 for any pr(r)
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram EqualizationHistogram Equalization
Discrete VersionDiscrete Version
rk = 第k階的灰階值, nk 是灰階值為 rk 之像素個數
1s0 k ≤≤
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram EqualizationHistogram Equalization
Histogram EqualizationHistogram Equalizationto produce an output image that has a uniformto produce an output image that has a uniformhistogramhistogram像素值均勻分佈可拉大影像明暗對比像素值均勻分佈可拉大影像明暗對比
proceduresprocedures求影像的求影像的HistogramHistogram求影像的機率密度函數求影像的機率密度函數
產生產生CDF(CDF(累積密度函數累積密度函數))T()T()使用使用T()T()處理每個像素處理每個像素
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram Matching (Specification)Histogram Matching (Specification)
Development of the methodDevelopment of the methodrr是來源影像灰階值是來源影像灰階值
zz是目的影像灰階值是目的影像灰階值
T( ): r -> sT( ): r -> sG( ): z->sG( ): z->s
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Discrete VersionDiscrete Version
3.3 Histogram Processing3.3 Histogram ProcessingHistogram Matching (Specification)Histogram Matching (Specification)
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram Matching (Specification)Histogram Matching (Specification)
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingHistogram Matching (Specification)Histogram Matching (Specification)
ImplementationImplementation1.1.取得影像的取得影像的HistogramHistogram2.2.使用公式使用公式(3.3-13)(3.3-13)計算每個計算每個 sskk
3.3.使用公式使用公式(3.3-14)(3.3-14)取得取得pz(z)pz(z)的轉換函式的轉換函式GG4.4.使用公式使用公式(3.3-17)(3.3-17)計算每個計算每個 zzkk
5.5.使用步驟使用步驟2-42-4的結果處理每個像素的結果處理每個像素取得取得 rrkk 的對映像素的對映像素sskk
取得取得 sskk的對映像素的對映像素zzkk
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Comparison between histogramComparison between histogramequalization and histogram matchingequalization and histogram matching
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingLocal EnhancementLocal Enhancement
步驟:1.定義方型或矩型的大小 2.針對每個像素 2.1.找出以目前像素為中心點之區塊內像素的histogram 2.2.使用histogram equalization/matching 方法取得像素對應值
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingUse of histogram statistice for image enhancementUse of histogram statistice for image enhancement
使用像素統計資訊使用像素統計資訊
子影像 Sx,y 的區域統資訊
mean value
N-Norm
2-NormStandard Deviation
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.3 Histogram Processing3.3 Histogram ProcessingUse of histogram statistice for image enhancementUse of histogram statistice for image enhancement
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
Block Size = 3x3
3.3 Histogram Processing3.3 Histogram ProcessingUse of histogram statistice for image enhancementUse of histogram statistice for image enhancement
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods E=4.0, k0=0.4, k1=0.02, k2=0.4
3.3 Histogram Processing3.3 Histogram ProcessingUse of histogram statistice for image enhancementUse of histogram statistice for image enhancement
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperationsOperations
performed on a pixel by pixel basis between two orperformed on a pixel by pixel basis between two ormore imagesmore imagesLogic OperationsLogic Operations
ANDANDORORNOTNOT
Arithmetic OperationsArithmetic OperationsSubstractionSubstractionAveragingAveraging
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperationsOperations
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperationsOperations
Image SubstractionImage Substraction
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperationsOperations
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
取得影像 = 原始影像 + 雜訊
平均結果
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperationsOperations
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperations - Operations - Image averagingImage averaging
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.4 Enhancement using Arithmetic/Logic3.4 Enhancement using Arithmetic/LogicOperations - Operations - Image averagingImage averaging
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.5 Basics of spatial filtering3.5 Basics of spatial filtering
MaskMaskfilter, kernel, templete, windowfilter, kernel, templete, window
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.5 Basics of spatial filtering3.5 Basics of spatial filtering
MaskMaskfilter, kernel, templete, windowfilter, kernel, templete, windowconverlution mask/kernelconverlution mask/kernel
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.6 Smoothing Spatial Filter3.6 Smoothing Spatial Filter
Smoothing filters are used forSmoothing filters are used forblurringblurringnoise reductionnoise reduction
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.6 Smoothing Spatial Filter3.6 Smoothing Spatial FilterSmoothing Linear FiltersSmoothing Linear Filters
Smoothing linear filtersSmoothing linear filtersalso called
averaging filterlowpass filter
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.6 Smoothing Spatial Filter3.6 Smoothing Spatial FilterSmoothing Linear FiltersSmoothing Linear Filters
Mask大小與影像平滑效果的關係
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.6 Smoothing Spatial Filter3.6 Smoothing Spatial FilterSmoothing Linear FiltersSmoothing Linear Filters
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.6 Smoothing Spatial Filter3.6 Smoothing Spatial FilterOrder-Statistics FiltersOrder-Statistics Filters
Non-linear filtersNon-linear filtersMedian filterMedian filter
exampleexampleunsorted (60,20,15,23,35,47,78,53,65)unsorted (60,20,15,23,35,47,78,53,65)sorted (15,20,23,35,sorted (15,20,23,35,4747,53,60,65,78),53,60,65,78)the median is the median is 4747
Max filterMax filterMin filterMin filter
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.6 Smoothing Spatial Filter3.6 Smoothing Spatial FilterOrder-Statistics FiltersOrder-Statistics Filters
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial Filters
Sharpening Spatial filters are used toSharpening Spatial filters are used tohighlight fine detailhighlight fine detailenhance detail that has been blurredenhance detail that has been blurred
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersFoundationFoundation
First-order derivativeFirst-order derivative
Second-order derivativeSecond-order derivative
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersFoundationFoundation
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
The LaplacianThe LaplacianDevelopment of the methodDevelopment of the method
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
FiltersFilters
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
SimplificationSimplification
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
Unsharp masking and high-boost filteringUnsharp masking and high-boost filtering
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of second Derivatives for enhancementUse of second Derivatives for enhancement
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of First Derivatives for enhancementUse of First Derivatives for enhancement
The Gradient (The Gradient (坡度坡度))
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of First Derivatives for enhancementUse of First Derivatives for enhancement
(d) and (e) are calledSobel Operators
(b) and (c) are refered asRoberts cross-gradient Operators
for 3 x 3 masks
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of First Derivatives for enhancementUse of First Derivatives for enhancement
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
水平強度
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of First Derivatives for enhancementUse of First Derivatives for enhancement
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
垂直強度
3.7 Sharpening Spatial Filters3.7 Sharpening Spatial FiltersUse of First Derivatives for enhancementUse of First Derivatives for enhancement
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Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.8 Combining Spatial Enhancement3.8 Combining Spatial EnhancementMethodsMethods
Digital Image Processing, 2nd ed.Digital Image Processing, 2nd ed.www.imageprocessingbook.com
© 2002 R. C. Gonzalez & R. E. Woods
3.8 Combining Spatial Enhancement3.8 Combining Spatial EnhancementMethodsMethods