CS482 CS482 Selected Topics in Digital Image Selected Topics in Digital Image Processing Processing م ي ح ر ل ا ن م ح ر ل له ا ل م ا س ب م ي ح ر ل ا ن م ح ر ل له ا ل م ا س بInstructor: Dr. Abdullah Basuhail ,CSD, FCIT, KAU, 1432H Chapter 2: Chapter 2: Digital Image Digital Image Fundamentals Fundamentals
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CS482 Selected Topics in Digital Image Processing بسم الله الرحمن الرحيم Instructor: Dr. Abdullah Basuhail,CSD, FCIT, KAU, 1432H Chapter 2: Digital Image.
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CS482 CS482
Selected Topics in Digital Image Selected Topics in Digital Image ProcessingProcessing
الرحيم الرحمن الله الرحيم بسم الرحمن الله بسم
Instructor: Dr. Abdullah Basuhail ,CSD, FCIT, KAU, 1432H
Chapter 2: Chapter 2: Digital Image Digital Image FundamentalsFundamentals
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 2
Visual PerceptionVisual Perception Mach bands: visual system tends to
undershoot or overshoot around the boundary of regions of different intensities
Simultaneous contrast: region’s perceived brightness does not depend on its intensity
Optical illusions: eye fills in nonexisting information or wrongly perceives geometrical properties of objects
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 6
Representing Digital ImagesRepresenting Digital Images Digital image
M N array L discrete intensities – power of 2
L = 2k
Integers in the interval [0, L - 1] Dynamic range: ratio of maximum / minimum intensity
Low: image has a dull, washed-out gray look Contrast: difference between highest and lowest
intensity High: image have high contrast
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 8
Representing Digital ImagesRepresenting Digital Images Digital image
# bits to store : b = M N k When M = N: b = N2k k-bit image: e.g. an image with 256 possible
discrete intensity values is called an 8-bit image
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 10
Spatial and Intensity Spatial and Intensity ResolutionResolution Resolution: dots (pixels) per unit distance dpi: dots per inch
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 12
Variation of Number of Intensity Variation of Number of Intensity LevelsLevels Reducing the number of bits from k=7 to
k=1 while keeping the image size constant Insufficient number of intensity levels in smooth
areas of digital image leads to false contouring
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 15
Image InterpolationImage Interpolation Using known data to estimate values at unknown
locations Used for zooming, shrinking, rotating, and geometric
corrections Nearest Neighbor interpolation
Use closest pixel to estimate the intensity simple but has tendency to produce artifact
Bilinear interpolation use 4 nearest neighbor to estimate the intensity Much better result
Bicubic interpolation Use 16 nearest neighbors of a point
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
Interpolation works by using known data to estimate values at unknown points .For example: if you wanted to know the temperature at noon, but only measured it
at 11AM and 1PM, you could estimate its value by performing a linear interpolation:
If you had an additional measurement at 11:30AM, you could see that the bulk of the temperature rise occurred before noon, and could use this additional data point
to perform a quadratic interpolation:
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
The more temperature measurements you have which are close to noon, the more sophisticated (and hopefully more accurate) your interpolation algorithm can be.
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
Nearest neighbor is the most basic and requires the least processing time of all the interpolation algorithms because it only considers one pixel — the closest one
to the interpolated point. This has the effect of simply making each pixel bigger.
NEAREST NEIGHBOR INTERPOLATION
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
The intensity value assigned to point (x,y) is obtained by equation where the sixteen coefficients are determined from the sixteen equations in sixteen unknowns that can be written using the sixteen nearest neighbours of point (x,y)
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 23
Arithmetic OperationsArithmetic Operations Array operations between images Carried out between corresponding pixel
pairs Four arithmetic
s(x, y) = f(x, y) + g(x, y)
d(x, y) = f(x, y) – g(x, y)
p(x, y) = f(x, y) g(x, y)
v(x, y) = f(x, y) ÷ g(x, y)
e.g. Averaging K different noisy images can decrease noise Used in the field of astronomy
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 29
Arithmetic OperationsArithmetic Operations To guarantee that the full range of an
arithmetic operation between images is captured into a fixed number of bits, the following approach is performed on image f
fm = f – min(f)
which creates an image whose minimum value is 0. Then the scaled image is
fs = K [ fm / max(fm)]
whose value is in the range [0, K]
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 30
Set and Logical OperationsSet and Logical Operations Sets can be used to let the elements of sets
be the coordinates of pixels (ordered pairs of integers) representing regions (objects) in an image Union Intersection Complement Difference
Logical operations OR AND NOT XOR
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 34
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 36
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 38
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 42
Vector and Matrix OperationsVector and Matrix Operations RGB images Multispectral images
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.
CS382, CSD, FCIT, KAU, KSA Based on textbook: Digital Image Processing, 3rd Edition, by Gonzalez and Woods Compiled by: Dr. Abdullah Basuhail , 1432H 44
Image TransformsImage Transforms Image processing tasks are best
formulated by Transforming the images Carrying the specified task un a transform
domain Applying the inverse transform
Digital Image Processing, 3rd ed.Digital Image Processing, 3rd ed.