SlideShare uma empresa Scribd logo
1 de 28
Baixar para ler offline
BRIEF INTRODUCTION OF
IMAGE ENHANCEMENT
TECHNIQUES
Presented By:
Bulbul Agrawal
M.Tech IInd year (IT Branch)
Outline:
 Introduction
Image enhancement techniques:
1. Spatial domain
2. Frequency domain
Applications
Conclusion
Introduction:
• Image Enhancement is the process of manipulating an image so that
the result is more suitable than the original for a specific application.
• The idea behind the enhancement technique is to bring out details that
are hidden or simple to highlight the certain features of interest in an
image.
Image enhancement techniques:
Spatial domain methods:
• The term spatial domain refers to the aggregate of pixels composing
an image.
• Spatial domain methods are procedures that operate directly on these
pixels.
• Spatial Domain processes will be denoted by the expression ,
g(x,y)= T[f(x,y)]
Where, g is the output, f is the input image and T is an operation on f
defined over some neighborhood of (x,y)
Cont…
According to the operations on the image pixels, it can be further
divided into 2 categories:
1. Point operations
2. Spatial operations
Point operation:
• It is the process of contrast enhancement.
• It is the process to produced an image of higher contrast than the
original by darkening a particular level.
• Enhancement at any point in an image depends only on the gray level
at that point, techniques in this category are often referred to as point
processing.
Point operation: Brightness modification
Increasing the brightness of an image:
g[m,n]=f[m,n]+k
Decreasing the brightness of an image:
g[m,n]=f[m,n]-k
Cont…
Fig: Example of brightness modification
Point operation: Inverse transformation
• Example is image negative.
• Negative transform exchanges dark values for light values and vice
versa.
• The negative transformation is defined by,
s=(L-1-r)
Where, L-1=maximum pixels value and
r= pixel value of an image
Cont…
Fig: Example of image inversion
Point operation: Thresholding
• Thresholding is required to extract a part of an image which contains
all the information.
• Thresholding is a part of more general segmentation problem.
• Pixels having intensity lower than the threshold T are set to zero and
the pixels having intensity greater than the threshold are set to 255.
• This type of hard thresholding allows us to obtain a binary image from
a grayscale image.
Cont…
Fig: Example of thresholding
Point operation: Gray-level slicing
• The purpose of gray-level slicing is to highlight a specific range of
gray values.
• Two different approaches can be adopted for gray-level slicing,
1. Gray-level slicing without preserving the background
2. Gray-level slicing with the background
Cont…
Without preserving the background:
• This displays high values for a range of interest and low values in
other areas.
• The main drawback of this approach is that the background
information is discarded.
With preserving the background:
• In gray-level slicing with background, the objective is to display high
values for the range of interest and original gray-level values in other
areas.
• This approach preserves the background of the image.
Cont…
Fig: Example of gray-level slicing
Point operation: Bit plane slicing
• The gray level of each pixel in a digital image is stored as one or more
bytes in computer.
• The three main goals of bit plane slicing are:
1. Converting a gray level image to binary image.
2. Representing an image with fewer bits and compressing the image to
a smaller size.
3. Enhancing the image by focusing.
Cont…
Fig: Example of bit-plane slicing
Spatial operations:
• Operations performed on local neighborhoods of input pixels
• Image is convolved with [FIR] finite impulse response filter called
spatial mask .
• Techniques such as :
- Noise smoothing
- Median filtering
- LP and HP filtering
- Zooming
Mask Operation:
• Mask is a small matrix useful for blurring, sharpening, edge-detection
and more.
• New image is generated by multiplying the input image with the mask
matrix.
• The output pixel values thus depend on the neighbouring input pixel
values.
• The mask may be of any dimension 3X3 4X4 ….
Histogram manipulation:
 Histogram:
• It is the another spatial domain technique.
• It is the plot of frequency of occurrence of an event.
• The histogram provides a convenient summary of the intensities in an
image.
Histogram equalization:
• Histogram equalization is a method in image processing of contrast
adjustment using the image’s histogram.
Cont…
Fig: Example of histogram and histogram equalization
Frequency Domain Methods:
• We simply compute the Fourier transform of the image to be
enhanced, multiply the result by a filter, and take the inverse transform
to produce the enhanced image.
• Filtering are done in FDM, like low-pass, high-pass, butterworth high-
pass filter, gaussian filter etc.
Applications:
• Image enhancement techniques are used to sharpen image features to
obtain a visually more pleasant, more detailed or less noisy output
image.
• Contrast enhancement can be achieved by histogram equalization.
• Blur reduction
Conclusion:
• The aim of image enhancement is to improve the information in
images for human viewers, or to provide ‘better’ input for other
automated image processing techniques.
• There is no general theory for determining what is ‘good’ image
enhancement when it comes to human perception. If it looks good, it is
good!
References:
• Digital image processing by Gonzalez and woods
• Digital image processing by S Jayaraman
• https://www.slideshare.net/Ayaelshiwi/image-enhancement-29760056
• https://www.techopedia.com/definition/26314/image-enhancement
• https://www.mathworks.com/discovery/image-enhancement.html
Image enhancement techniques
Image enhancement techniques

Mais conteúdo relacionado

Mais procurados

Chapter 9 morphological image processing
Chapter 9   morphological image processingChapter 9   morphological image processing
Chapter 9 morphological image processingAhmed Daoud
 
Histogram Processing
Histogram ProcessingHistogram Processing
Histogram ProcessingAmnaakhaan
 
Introduction to Image Compression
Introduction to Image CompressionIntroduction to Image Compression
Introduction to Image CompressionKalyan Acharjya
 
Image enhancement techniques
Image enhancement techniquesImage enhancement techniques
Image enhancement techniquesSaideep
 
Digital Image Processing: An Introduction
Digital Image Processing: An IntroductionDigital Image Processing: An Introduction
Digital Image Processing: An IntroductionMostafa G. M. Mostafa
 
Chapter 6 color image processing
Chapter 6 color image processingChapter 6 color image processing
Chapter 6 color image processingasodariyabhavesh
 
Image Restoration (Digital Image Processing)
Image Restoration (Digital Image Processing)Image Restoration (Digital Image Processing)
Image Restoration (Digital Image Processing)Kalyan Acharjya
 
Digital Image Processing: Image Enhancement in the Spatial Domain
Digital Image Processing: Image Enhancement in the Spatial DomainDigital Image Processing: Image Enhancement in the Spatial Domain
Digital Image Processing: Image Enhancement in the Spatial DomainMostafa G. M. Mostafa
 
Digital Image restoration
Digital Image restorationDigital Image restoration
Digital Image restorationMd Shabir Alam
 
Hough Transform By Md.Nazmul Islam
Hough Transform By Md.Nazmul IslamHough Transform By Md.Nazmul Islam
Hough Transform By Md.Nazmul IslamNazmul Islam
 
Chapter 5 Image Processing: Fourier Transformation
Chapter 5 Image Processing: Fourier TransformationChapter 5 Image Processing: Fourier Transformation
Chapter 5 Image Processing: Fourier TransformationVarun Ojha
 

Mais procurados (20)

Segmentation
SegmentationSegmentation
Segmentation
 
SPATIAL FILTER
SPATIAL FILTERSPATIAL FILTER
SPATIAL FILTER
 
Chapter 9 morphological image processing
Chapter 9   morphological image processingChapter 9   morphological image processing
Chapter 9 morphological image processing
 
Histogram Processing
Histogram ProcessingHistogram Processing
Histogram Processing
 
Introduction to Image Compression
Introduction to Image CompressionIntroduction to Image Compression
Introduction to Image Compression
 
Image Restoration
Image RestorationImage Restoration
Image Restoration
 
Image enhancement techniques
Image enhancement techniquesImage enhancement techniques
Image enhancement techniques
 
image enhancement
 image enhancement image enhancement
image enhancement
 
Digital Image Processing: An Introduction
Digital Image Processing: An IntroductionDigital Image Processing: An Introduction
Digital Image Processing: An Introduction
 
Chapter 6 color image processing
Chapter 6 color image processingChapter 6 color image processing
Chapter 6 color image processing
 
Image Restoration (Digital Image Processing)
Image Restoration (Digital Image Processing)Image Restoration (Digital Image Processing)
Image Restoration (Digital Image Processing)
 
Digital Image Processing: Image Enhancement in the Spatial Domain
Digital Image Processing: Image Enhancement in the Spatial DomainDigital Image Processing: Image Enhancement in the Spatial Domain
Digital Image Processing: Image Enhancement in the Spatial Domain
 
Image segmentation
Image segmentationImage segmentation
Image segmentation
 
Digital Image restoration
Digital Image restorationDigital Image restoration
Digital Image restoration
 
Image enhancement
Image enhancementImage enhancement
Image enhancement
 
Hough Transform By Md.Nazmul Islam
Hough Transform By Md.Nazmul IslamHough Transform By Md.Nazmul Islam
Hough Transform By Md.Nazmul Islam
 
Hit and-miss transform
Hit and-miss transformHit and-miss transform
Hit and-miss transform
 
Data Redundacy
Data RedundacyData Redundacy
Data Redundacy
 
Psuedo color
Psuedo colorPsuedo color
Psuedo color
 
Chapter 5 Image Processing: Fourier Transformation
Chapter 5 Image Processing: Fourier TransformationChapter 5 Image Processing: Fourier Transformation
Chapter 5 Image Processing: Fourier Transformation
 

Semelhante a Image enhancement techniques

Image enhancement lecture
Image enhancement lectureImage enhancement lecture
Image enhancement lectureISRAR HUSSAIN
 
Image enhancement in spatial domain.ppt
Image enhancement in spatial domain.pptImage enhancement in spatial domain.ppt
Image enhancement in spatial domain.pptpravin patil
 
Digital image processing techniques
Digital image processing techniquesDigital image processing techniques
Digital image processing techniquesShab Bi
 
Unit 2. Image Enhancement in Spatial Domain.pptx
Unit 2. Image Enhancement in Spatial Domain.pptxUnit 2. Image Enhancement in Spatial Domain.pptx
Unit 2. Image Enhancement in Spatial Domain.pptxswagatkarve
 
Digital image processing - Image Enhancement (MATERIAL)
Digital image processing  - Image Enhancement (MATERIAL)Digital image processing  - Image Enhancement (MATERIAL)
Digital image processing - Image Enhancement (MATERIAL)Mathankumar S
 
Digital Image Processing - Image Enhancement
Digital Image Processing  - Image EnhancementDigital Image Processing  - Image Enhancement
Digital Image Processing - Image EnhancementMathankumar S
 
Digital image processing & computer graphics
Digital image processing & computer graphicsDigital image processing & computer graphics
Digital image processing & computer graphicsAnkit Garg
 
DIP Notes Unit-1 PPT.pdf
DIP Notes Unit-1 PPT.pdfDIP Notes Unit-1 PPT.pdf
DIP Notes Unit-1 PPT.pdfGaurav Sharma
 
Image Enhancement in the Spatial Domain U2.ppt
Image Enhancement in the Spatial Domain U2.pptImage Enhancement in the Spatial Domain U2.ppt
Image Enhancement in the Spatial Domain U2.pptssuser7ec6af
 
Image enhancement
Image enhancementImage enhancement
Image enhancementKuppusamy P
 
Digital Image Processing_ ch2 enhancement spatial-domain
Digital Image Processing_ ch2 enhancement spatial-domainDigital Image Processing_ ch2 enhancement spatial-domain
Digital Image Processing_ ch2 enhancement spatial-domainMalik obeisat
 
Image processing and compression.pptx
Image processing and compression.pptxImage processing and compression.pptx
Image processing and compression.pptxdudoo1
 
Image processing second unit Notes
Image processing second unit NotesImage processing second unit Notes
Image processing second unit NotesAAKANKSHA JAIN
 

Semelhante a Image enhancement techniques (20)

Image enhancement lecture
Image enhancement lectureImage enhancement lecture
Image enhancement lecture
 
Image enhancement in spatial domain.ppt
Image enhancement in spatial domain.pptImage enhancement in spatial domain.ppt
Image enhancement in spatial domain.ppt
 
Digital image processing techniques
Digital image processing techniquesDigital image processing techniques
Digital image processing techniques
 
Unit 2. Image Enhancement in Spatial Domain.pptx
Unit 2. Image Enhancement in Spatial Domain.pptxUnit 2. Image Enhancement in Spatial Domain.pptx
Unit 2. Image Enhancement in Spatial Domain.pptx
 
Digital image processing - Image Enhancement (MATERIAL)
Digital image processing  - Image Enhancement (MATERIAL)Digital image processing  - Image Enhancement (MATERIAL)
Digital image processing - Image Enhancement (MATERIAL)
 
Digital Image Processing - Image Enhancement
Digital Image Processing  - Image EnhancementDigital Image Processing  - Image Enhancement
Digital Image Processing - Image Enhancement
 
Digital image processing & computer graphics
Digital image processing & computer graphicsDigital image processing & computer graphics
Digital image processing & computer graphics
 
aip.pptx
aip.pptxaip.pptx
aip.pptx
 
DIP Notes Unit-1 PPT.pdf
DIP Notes Unit-1 PPT.pdfDIP Notes Unit-1 PPT.pdf
DIP Notes Unit-1 PPT.pdf
 
DIP Lecture 7-9.pdf
DIP Lecture 7-9.pdfDIP Lecture 7-9.pdf
DIP Lecture 7-9.pdf
 
Image Enhancement in the Spatial Domain U2.ppt
Image Enhancement in the Spatial Domain U2.pptImage Enhancement in the Spatial Domain U2.ppt
Image Enhancement in the Spatial Domain U2.ppt
 
Image enhancement
Image enhancementImage enhancement
Image enhancement
 
Digital Image Processing_ ch2 enhancement spatial-domain
Digital Image Processing_ ch2 enhancement spatial-domainDigital Image Processing_ ch2 enhancement spatial-domain
Digital Image Processing_ ch2 enhancement spatial-domain
 
F0342032038
F0342032038F0342032038
F0342032038
 
Ijcatr04051016
Ijcatr04051016Ijcatr04051016
Ijcatr04051016
 
Image processing and compression.pptx
Image processing and compression.pptxImage processing and compression.pptx
Image processing and compression.pptx
 
Image processing second unit Notes
Image processing second unit NotesImage processing second unit Notes
Image processing second unit Notes
 
ACMP340.pptx
ACMP340.pptxACMP340.pptx
ACMP340.pptx
 
Chap5 imange enhancemet
Chap5 imange enhancemetChap5 imange enhancemet
Chap5 imange enhancemet
 
Digital image processing
Digital image processingDigital image processing
Digital image processing
 

Último

EPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptxEPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptxJoseeMusabyimana
 
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...Amil baba
 
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...amrabdallah9
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical SensorTanvir Moin
 
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdfsdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdfJulia Kaye
 
cloud computing notes for anna university syllabus
cloud computing notes for anna university syllabuscloud computing notes for anna university syllabus
cloud computing notes for anna university syllabusViolet Violet
 
The relationship between iot and communication technology
The relationship between iot and communication technologyThe relationship between iot and communication technology
The relationship between iot and communication technologyabdulkadirmukarram03
 
Nodal seismic construction requirements.pptx
Nodal seismic construction requirements.pptxNodal seismic construction requirements.pptx
Nodal seismic construction requirements.pptxwendy cai
 
solar wireless electric vechicle charging system
solar wireless electric vechicle charging systemsolar wireless electric vechicle charging system
solar wireless electric vechicle charging systemgokuldongala
 
Power System electrical and electronics .pptx
Power System electrical and electronics .pptxPower System electrical and electronics .pptx
Power System electrical and electronics .pptxMUKULKUMAR210
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxKISHAN KUMAR
 
Test of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptxTest of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptxHome
 
How to Write a Good Scientific Paper.pdf
How to Write a Good Scientific Paper.pdfHow to Write a Good Scientific Paper.pdf
How to Write a Good Scientific Paper.pdfRedhwan Qasem Shaddad
 
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxUNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxrealme6igamerr
 
me3493 manufacturing technology unit 1 Part A
me3493 manufacturing technology unit 1 Part Ame3493 manufacturing technology unit 1 Part A
me3493 manufacturing technology unit 1 Part Akarthi keyan
 
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS Bahzad5
 
Guardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSecGuardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSecTrupti Shiralkar, CISSP
 
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Amil baba
 
Graphics Primitives and CG Display Devices
Graphics Primitives and CG Display DevicesGraphics Primitives and CG Display Devices
Graphics Primitives and CG Display DevicesDIPIKA83
 

Último (20)

Lecture 4 .pdf
Lecture 4                              .pdfLecture 4                              .pdf
Lecture 4 .pdf
 
EPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptxEPE3163_Hydro power stations_Unit2_Lect2.pptx
EPE3163_Hydro power stations_Unit2_Lect2.pptx
 
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
Popular-NO1 Kala Jadu Expert Specialist In Germany Kala Jadu Expert Specialis...
 
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical Sensor
 
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdfsdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
 
cloud computing notes for anna university syllabus
cloud computing notes for anna university syllabuscloud computing notes for anna university syllabus
cloud computing notes for anna university syllabus
 
The relationship between iot and communication technology
The relationship between iot and communication technologyThe relationship between iot and communication technology
The relationship between iot and communication technology
 
Nodal seismic construction requirements.pptx
Nodal seismic construction requirements.pptxNodal seismic construction requirements.pptx
Nodal seismic construction requirements.pptx
 
solar wireless electric vechicle charging system
solar wireless electric vechicle charging systemsolar wireless electric vechicle charging system
solar wireless electric vechicle charging system
 
Power System electrical and electronics .pptx
Power System electrical and electronics .pptxPower System electrical and electronics .pptx
Power System electrical and electronics .pptx
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptx
 
Test of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptxTest of Significance of Large Samples for Mean = µ.pptx
Test of Significance of Large Samples for Mean = µ.pptx
 
How to Write a Good Scientific Paper.pdf
How to Write a Good Scientific Paper.pdfHow to Write a Good Scientific Paper.pdf
How to Write a Good Scientific Paper.pdf
 
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxUNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
 
me3493 manufacturing technology unit 1 Part A
me3493 manufacturing technology unit 1 Part Ame3493 manufacturing technology unit 1 Part A
me3493 manufacturing technology unit 1 Part A
 
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS GENERAL CONDITIONS  FOR  CONTRACTS OF CIVIL ENGINEERING WORKS
GENERAL CONDITIONS FOR CONTRACTS OF CIVIL ENGINEERING WORKS
 
Guardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSecGuardians and Glitches: Navigating the Duality of Gen AI in AppSec
Guardians and Glitches: Navigating the Duality of Gen AI in AppSec
 
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
Best-NO1 Best Rohani Amil In Lahore Kala Ilam In Lahore Kala Jadu Amil In Lah...
 
Graphics Primitives and CG Display Devices
Graphics Primitives and CG Display DevicesGraphics Primitives and CG Display Devices
Graphics Primitives and CG Display Devices
 

Image enhancement techniques

  • 1. BRIEF INTRODUCTION OF IMAGE ENHANCEMENT TECHNIQUES Presented By: Bulbul Agrawal M.Tech IInd year (IT Branch)
  • 2. Outline:  Introduction Image enhancement techniques: 1. Spatial domain 2. Frequency domain Applications Conclusion
  • 3. Introduction: • Image Enhancement is the process of manipulating an image so that the result is more suitable than the original for a specific application. • The idea behind the enhancement technique is to bring out details that are hidden or simple to highlight the certain features of interest in an image.
  • 5. Spatial domain methods: • The term spatial domain refers to the aggregate of pixels composing an image. • Spatial domain methods are procedures that operate directly on these pixels. • Spatial Domain processes will be denoted by the expression , g(x,y)= T[f(x,y)] Where, g is the output, f is the input image and T is an operation on f defined over some neighborhood of (x,y)
  • 6. Cont… According to the operations on the image pixels, it can be further divided into 2 categories: 1. Point operations 2. Spatial operations
  • 7. Point operation: • It is the process of contrast enhancement. • It is the process to produced an image of higher contrast than the original by darkening a particular level. • Enhancement at any point in an image depends only on the gray level at that point, techniques in this category are often referred to as point processing.
  • 8. Point operation: Brightness modification Increasing the brightness of an image: g[m,n]=f[m,n]+k Decreasing the brightness of an image: g[m,n]=f[m,n]-k
  • 9. Cont… Fig: Example of brightness modification
  • 10. Point operation: Inverse transformation • Example is image negative. • Negative transform exchanges dark values for light values and vice versa. • The negative transformation is defined by, s=(L-1-r) Where, L-1=maximum pixels value and r= pixel value of an image
  • 11. Cont… Fig: Example of image inversion
  • 12. Point operation: Thresholding • Thresholding is required to extract a part of an image which contains all the information. • Thresholding is a part of more general segmentation problem. • Pixels having intensity lower than the threshold T are set to zero and the pixels having intensity greater than the threshold are set to 255. • This type of hard thresholding allows us to obtain a binary image from a grayscale image.
  • 13. Cont… Fig: Example of thresholding
  • 14. Point operation: Gray-level slicing • The purpose of gray-level slicing is to highlight a specific range of gray values. • Two different approaches can be adopted for gray-level slicing, 1. Gray-level slicing without preserving the background 2. Gray-level slicing with the background
  • 15. Cont… Without preserving the background: • This displays high values for a range of interest and low values in other areas. • The main drawback of this approach is that the background information is discarded. With preserving the background: • In gray-level slicing with background, the objective is to display high values for the range of interest and original gray-level values in other areas. • This approach preserves the background of the image.
  • 16. Cont… Fig: Example of gray-level slicing
  • 17. Point operation: Bit plane slicing • The gray level of each pixel in a digital image is stored as one or more bytes in computer. • The three main goals of bit plane slicing are: 1. Converting a gray level image to binary image. 2. Representing an image with fewer bits and compressing the image to a smaller size. 3. Enhancing the image by focusing.
  • 18. Cont… Fig: Example of bit-plane slicing
  • 19. Spatial operations: • Operations performed on local neighborhoods of input pixels • Image is convolved with [FIR] finite impulse response filter called spatial mask . • Techniques such as : - Noise smoothing - Median filtering - LP and HP filtering - Zooming
  • 20. Mask Operation: • Mask is a small matrix useful for blurring, sharpening, edge-detection and more. • New image is generated by multiplying the input image with the mask matrix. • The output pixel values thus depend on the neighbouring input pixel values. • The mask may be of any dimension 3X3 4X4 ….
  • 21. Histogram manipulation:  Histogram: • It is the another spatial domain technique. • It is the plot of frequency of occurrence of an event. • The histogram provides a convenient summary of the intensities in an image. Histogram equalization: • Histogram equalization is a method in image processing of contrast adjustment using the image’s histogram.
  • 22. Cont… Fig: Example of histogram and histogram equalization
  • 23. Frequency Domain Methods: • We simply compute the Fourier transform of the image to be enhanced, multiply the result by a filter, and take the inverse transform to produce the enhanced image. • Filtering are done in FDM, like low-pass, high-pass, butterworth high- pass filter, gaussian filter etc.
  • 24. Applications: • Image enhancement techniques are used to sharpen image features to obtain a visually more pleasant, more detailed or less noisy output image. • Contrast enhancement can be achieved by histogram equalization. • Blur reduction
  • 25. Conclusion: • The aim of image enhancement is to improve the information in images for human viewers, or to provide ‘better’ input for other automated image processing techniques. • There is no general theory for determining what is ‘good’ image enhancement when it comes to human perception. If it looks good, it is good!
  • 26. References: • Digital image processing by Gonzalez and woods • Digital image processing by S Jayaraman • https://www.slideshare.net/Ayaelshiwi/image-enhancement-29760056 • https://www.techopedia.com/definition/26314/image-enhancement • https://www.mathworks.com/discovery/image-enhancement.html