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Digital Image Processing
Chapter 2: Digital Image Fundamentals
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Elements of Visual Perception
Structure of the human eye
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Rods and cones in the retina
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Image formation in the eye
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Brightness adaptation and discrimination
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Brightness discrimination
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Weber ratio
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Perceived brightness
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Simultaneous contrast
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Optical illusion
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Light and the Electromagnetic Spectrum
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Wavelength
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Image Sensing and Acquisition
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Image acquisition using a single sensor
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Using sensor strips
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A simple image formation model
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Illumination and reflectance
Illumination and transmissivity
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Image Sampling and Quantization
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Sampling and quantization
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Representing digital images
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Number of storage bits
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Spatial and gray-level resolution
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Subsampled and resampled
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Varying the number of gray levels
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Varying the number of gray levels
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N and k in different-details images
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Isopreference
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Moire pattern
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Zooming and shrinking
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Some Basic Relationships Between Pixels
Neighbors of a pixel : 4-neighbors of p , , , : four diagonal neighbors of p , , , : 8-neighbors of p and
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Adjacency : The set of gray-level values used to define adjacency
4-adjacency: Two pixels p and q with values from V are 4-adjacency if q is in the set 8-adjacency: Two pixels p and q with values from V are 8-adjacency if q is in the set
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m-adjacency (mixed adjacency): Two pixels p and q with values from V are m-adjacency if
q is in , or q is in and the set has no pixels whose values are from V
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Subset adjacency S1 and S2 are adjacent if some pixel in S1 is adjacent to some pixel in S2 Path A path from p with coordinates to pixel q with coordinates is a sequence of distinct pixels with coordinates , ,…, where = , = , and pixels and are adjacent
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Region We call R a region of the image if R is a connected set Boundary The boundary of a region R is the set of pixels in the region that have one or more neighbors that are not in R Edge Pixels with derivative values that exceed a preset threshold
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Distance measures Euclidean distance City-block distance
Chessboard distance
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Linear operation distance: The shortest m-path between the points
H is said to be a linear operator if, for any two images f and g and any two scalars a and b,
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Example Zooming and Shrinking Images by Pixel Replication
(a) Write a computer program capable of zooming and shrinking an image by pixel replication. Assume that the desired zoom/shrink factors are integers. You may ignore aliasing effects. You will need to download Fig. 2.19(a). (b) Download Fig (a) and use your program to shrink the image from 1024 x 1024 to 256 x 256 pixels. (c) Use your program to zoom the image in (b) back to 1024 x Explain the reasons for their differences.
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Fig2.19(a).bmp subsample.c resample.c
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