eele 5310: digital image processing lecture 1 eng. ruba a. salamah rsalamah @ iugaza.edu
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EELE 5310: Digital Image Processing Lecture 1 Eng. Ruba A. Salamah Rsalamah @ iugaza.Edu. To Cover the basic theory and algorithms that are widely used in digital image processing. To Expose students to current technologies and issues that are specific to image processing systems. - PowerPoint PPT PresentationTRANSCRIPT
Course Objectives:
To Cover the basic theory and algorithms that are widely used in digital image processing.
To Expose students to current technologies and issues that are specific to image processing systems.
To Develop hands-on experience in using computers to process images.
Familiarize with MATLAB Image Processing Toolbox.
Recommended Textbook
• “Digital Image Processing” by R.C. Gonzalez and R.E. Woods, 3rd edition, Pearson Prentice Hall, 2008
• Additional readings on the class website
Prerequisites:
Knowledge of the following three areas:
-Linear Algebra.
-Elementary Probability Theory.
-Signals and Systems.
Grading Policy
Quizzes 15%
H.W 10%
Attendance 10%
Projects 20%
FinalExam45%
Course outline
Introduction Digital Image Fundamentals Image Enhancement in the Spatial Domain Image Enhancement in the Frequency Domain Image Restoration Image Compression Image Segmentation Representation and Description
What is a Digital Image?
A finite array of data values
What is Image Processing
Processing digital images by means of a digital computer.
Image processing typically attempts to accomplish one of three things:
Restoring Images
Enhancing Images
Understanding Images
• Restoration takes a corrupted image and attempts to recreate a clean original
• Enhancement alters an image to makes its meaning clearer to human observers
• Understanding usually attempts to mimic the human visual system in extracting meaning from an image
Three Types of Processes Low-level Processes :
Involve primitive operations such as image preprocessing to reduce noise, contrast
enhancement, and image sharpening.
A low-level process is characterized by the fact that both its inputs and outputs are
images.
Mid-level Processes:
Involves tasks such as segmentation (partitioning an image into regions or objects),
description of those objects to reduce them to a form suitable for machine learning ,
and classification(recognition) of individual objects.
Its inputs generally are images, but its outputs are attributes extracted from those
images (e.g., edges, contours, and the identity of individual objects).
Three Types of Processes
High-level Processes :
Processing involves "making sense“ of an ensemble
of recognized objects, as in image analysis, and, at
the far end of the continuum, performing the
cognitive functions normally associated with vision.
Applications
Processing of remote-sensed images via satellite.
Radar, MRI, Ultrasonic image processing.
Noise Reduction.
Character recognition.
Automatic inspection of industrial parts.
Content based image retrieval.
Biometrics.
Target tracking.
Sources of Energy for Image Formation The principle energy source for images is the EM
spectrum
Other sources include ultrasonic, electronic, and synthetic images.
Some Applications -- Medical Diagnostics
Some Applications -- MRI
Imaging in Radio Band
Some Applications -- Microscopy
Some Applications -- Industrial Inspection
Some Applications -- Remote Sensing
Some Applications -- Transmitting Images
Key Stages in Digital Image Processing
Image Acquisition
Image Enhancement
Image Restoration
Morphological Processing
Segmentation
Object Recognition
Image Representation & Description
Image Compression
Colour Image Processing
Image Acquisition
Image Sampling and Quantization
Digitalization of an analog signal involves two operations: Sampling: Degitizing the x- and y-coordinates. Quantization: Degitizing the amplitude values.
Image Sampling and Quantization
Representing Ddigital Images
A digital image is composed of M rows and N columns of pixels each storing a value.
Representing Ddigital Images
A complete M × N digital image can be written in the following compact matrix form:
The right side of this equation is by definition a digital image. Each element of his matrix array is called an image element, picture element, pixel, or pel.
Storage Capacity
A digital image can be represented as a 2-D function whose coordinates and amplitude values are integers.
The digitization process requires decisions about values for M, N, and for the number, L, of discrete gray levels allowed for each pixel.
The discrete levels are equally spaced integers in the interval [0, L-1], this range is called the dynamic range of an image.
Images with high dynamic range will have high contrast and (vise versa).
The number, b, of bits required to store a digitized image is: b = M x N x k
Storage Capacity
Spatial Resolution
The spatial resolution of an image is determined by how sampling was carried out
Spatial resolution simply refers to the smallest discernable detail in an image
Vision specialists well
often talk about pixel size Graphic designers will talk
about dots per inch (dpi)
Gray-level Resolution
Gray-level resolution is the smallest discernible change in gray level.
Due to hardware considerations, the number of gray levels is usually an integer power of 2. The most common number is 8 bits, i.e 256 levels.
It is common to refer to an L-level digital image of size MxN as having a spatial resolution of MxN pixels and a gray-level resolution of L levels.
Effects of Varying Spatial Resolution
Effects of Varying Spatial Resolution
Effects of Varying Gray-Level Resolution
Ridge like structure False contouring
Effects of Varying Gray-Level Resolution
Effects of Varying Gray-Level Resolution As a very rough rule of thumb, and assuming
powers of 2 for convenience, images of size 256*256 pixels and 64 gray levels are about the smallest images that can be expected to be reasonably free of objectionable sampling checkerboards and false contouring.
Zooming Digital Images
Zooming (digital image) can be viewed by oversampling (continuous image).
1- Creation of new pixel locations
2- Assign a gray level value to this new location using:
Nearest neighbor interpolation (Pixel replication )
Bilinear interpolation
Pixel Replication
Applicable to increase the size of an image an integer number of times.
We can duplicate each column and each row. New locations are duplicates of old locations.
Fast but produces checkerboard effect that is particularly objectionable at high factor of magnification.
x4
Bilinear Interpolation
Using the four nearest neighbors of a point. Let (x’, y’) denote the coordinates of a point in
the zoomed image, the gray value v(x’,y’) will be set to:
V(x’,y’)=ax’ + by’ +cx’y’ + d Where the four coefficients are determined from
the four equations in four unknowns using the four nearest neighbors of point (x’, y’).
Image Zooming
Shrinking Digital Image
Shrinking (digital image) can be viewed by undersampling (continuous image).
1- Deletion of row column pixels.
2- Assign a gray level value using :
Nearest neighbor interpolation
Bilinear interpolation
Relationships Between Pixels
1- Neighbors of a Pixel:
The 4- neighbors of pixel p are:
N4(p)
The 4- diagonal neighbors are:
ND(p)
The 8-neighbors are :
N8(p)
P
P
P
Relationships Between Pixels
Connectivity between pixels is important Because it is used in establishing boundaries of objects and components of regions in an image
Two pixels are connected if: They are neighbors (i.e. adjacent in some sense -- e.g.
N4(p), N8(p), …) Their gray levels satisfy a specified criterion of
similarity (e.g. equality, …)
Adjacency
Let V be the set of intensity used to define djacency; e.g. V={1} in a binary image or V={100,101,102,…,120} inn a gray-scale image.
We consider three types of adjacency :
1. 4-adjacency: Two pixels p and q with values from V are 4-adjacent if
q is in the set N4(p).
2. 8-adjacency:
Two pixels p and q with values from V are 8- adjacent if q is in the set N8(p).
Adjacency
3. m-adjacency (mixed adjacency): Two pixels p and q with values from V are m- adjacent if :
(i) q is in N4(p),or
(ii) q is in ND( p)and N4( p)∩ N4(q) is empty
Two image subsets S1 and S2 are adjacent if some pixel in S1 is adjacent
to some pixel in S2.
Digital path (curve)
A (digital) path (or curve) from pixel p with coordinates (x, y)
to pixel q with coordinates (s, t) is a sequence of distinct pixels
with coordinates
(x0, y0), (x1,y1), ……., (xn, yn)
where (x0, y0) = (x, y), (xn, yn) = (s, t), and pixels (xi, yi) and (xi-1,
yi-1) are adjacent for 1≤ i ≤ n. In this case, n is the length of the
path. If (x0, y0) = (xn, yn) the path is a closed path.
Regions Let S represent a subset of pixels in an image.
Two pixels p and q are said to be connected in S if
there exists a path between them consisting of pixels
in S.
For any pixel p in S, the set of pixels that are
connected to it in S is called a connected component
of S.
If S only has one connected component, then it is
called a connected set.
Let R be a subset of pixels in an image. We call R a
region of the image if R is a connected set
Region Boundary and edge
The boundary (also called border or contour) of
a region R is the set of pixels in the region that
have one or more neighbors that are not in R.
An edge is a “local” concept that is based on a
measure of gray-level discontinuity at a point.
Distance Measures
Distance Measures
Distance Measures
Distance Measures
The Dm distance: the shortest m-path between the points.
Image Operations on a Pixel Basis
when we refer to an operation like “dividing one image by another,” we mean specifically that the division is carried out between corresponding pixels in the two images.
Linear and Nonlinear Operations
H is a Linear operator if:
H(af + bg) = aH(f) + bH(g)
Where a and b are two scalars and g are two images.
(i.e) the result of applying a linear operator to the sum of two images is
identical to applying the operator to the images individually, multiplying
the results by the appropriate constants, and then adding those results.
For example, an operator whose function is to compute the sum of K
images is a linear operator. An operator that computes the absolute value of
the difference of two images is not.
Reading
Sections 2.4 and 2.5 of the textbook.
Homework
Answer the following problems from the text book:
9, 11, 15,18, 19