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Digital Image Processing
Dr. Saad M. Saad Darwish Associate Prof. of computer science
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What is an image? - The bitmap representation
Also called “raster or pixel maps” representation
An image is broken up into a grid
pixel
Gray level
Original picture Digital image
f(x, y) I[i, j] or I[x, y]
x
y
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What is an image? - The vector representation
Object-oriented representationDoes not show information of individual
pixel, but information of an object (circle, line, square, etc.)
Circle(100, 20, 20)Line(xa1, ya1, xa2, ya2)Line(xb1, yb1, xb2, yb2)Line(xc1, yc1, xc2, yc2)Line(xd1, yd1, xd2, yd2)
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Comparison
Bitmap– Can represent images with
complex variations in colors, shades, shapes.
– Larger image size
– Fixed resolution
– Easier to implement
Vector– Can only represent simple
line drawings (CAD), shapes, shadings, etc.
– Efficient
– Flexible
– Difficult to implement
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Why image processing?
Application
– Fingerprint retrieval
– Automatic target recognition
– Industrial inspection
– Medical imaging
– and more …Can commercial software do all the work?
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Some clarification
Image & Graphics Graphics are visual presentations on some surface, examples are
photographs, drawings, graphs, diagrams, symbols, geometric, maps, engineering drawings, or other images.
Image processing & Computer vision Computer vision is a field that includes methods for acquiring, processing,
analyzing, and understanding images. Image processing & Image understanding Image understanding produces descriptions of both the images (extracting
features from images) and the world scenes that the images represent."
Image processing & Pattern recognition
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Goals of image processing
Image improvement
– Improving the visual appearance of images to a human viewer
Image analysis
– Preparing images for measurement of the features and structures present
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What to learn?
ImageAcquisition
ImageEnhancement
ImageRestoration
ImageCompression
ImageSegmentation
Representation &Description
Recognition& Interpretation
Knowledge Base
Preprocessing – low levelImage Improvement
ImageCoding
MorphologicalImage Processing
WaveletAnalysis
High-level IPImage Analysis
Video camera Infrared camera Range camera Line-scan camera Hyperspectral camera Omni-directional camera and more …
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Image acquisition
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Some simple operations
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Image enhancement
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Movie film restoration
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Image restoration
The purpose of image restoration is to "compensate for" or "undo" defects which degrade an image.
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Image correction
Geometric correction: Operations intended to restore or compensate the distortions of an image in geometry
Radiometric correction: Operations intended to remove systematic or random noise affecting the amplitude (brightness) of an image
Image warping geometric transformation
Image warping is the process of digitally manipulating an image such that any shapes portrayed in the image have been significantly distorted.
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Image warping – another example
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Image Segmentation
The result of image segmentation is a set of segments that collectively cover the entire image, or a set of contours extracted from the image The goal of image segmentation is to cluster pixels into salient image regions,
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Image description
OCR – Optical character recognition, license plate recognition
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Beyond
Content-based image retrievalHuman identificationMulti-sensor data fusionHexagonal pixelSteganography
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Image processing for fine arts
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Real-world reasoning demo
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How to address pixels of an image?
int i, j, k;int nr, // number of rows nc, // number of columns nchan;// number of channels
nr = 128; nc = 128; nchan = 3;for (i=0; i<nr; i++) { for (j=0; j<nc; j++) { for (k=0; k<nchan; j++) { do the processing on (i,j,k); ……… } }}
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j
(i, j) (i, j+1)(i, j-1)
(i-1, j) (i-1, j+1)
(i+1, j+1)(i+1, j)
(i-1, j-1)
(i+1, j-1)i
(row)
(column)
4-neighborhood 8-neighborhood
Types of neighborhoods
Neighbors of a pixel