Outline
• Announcements
– Projects
• Local operations
– Histograms
– Point operations
– Algebraic operations
• Applications
– Image morphing
Announcements
• Projects
– Based on my programs
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•
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Need to get familiar with my programs
Find the database you are interested in on the web
Change my program to get the system work
Tune parameters to improve performance
– Based on a paper or your idea
• Need to talk to me either this week or next week
• Make sure that it is doable during the time framework
• Report and in-class presentation
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Announcements
• Research papers
– Need to talk to me on the papers or the subjects
you are interested in
– Decide on the topics within two weeks
– Write a research paper for each topic
– Do a presentation in class for each topic
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Local Operations
• A image can be represented by a matrix
• Neighborhood
• Local operations
– Operations whose output depends only on pixels
within a local neighborhood
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Neighborhoods
• 4-neighborhood
– For pixel (i, j)
{(i-1, j), (i+1, j), (i, j-1), (i, j+1)}
• 8-neighborhood
– For pixel (i, j)
{(i-1, j), (i+1, j), (i, j-1), (i, j+1)
(i-1, j-1), (i+1, j+1), (i+1, j-1), (i-1, j+1)}
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Point Operations
• A point operation takes a single input image
into a single output image in such a way that
each output’s pixel value depends only upon
the pixel value of the corresponding input
pixel
– Contrast enhancement
– Contrast stretching
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Types of Point Operations
• Linear point operations
– PO = f(PI) = a PI + b
• Nonlinear point operations
– PO = f(PI) where f is a nonlinear function
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Image Histograms
• Histogram
– The histogram is the function showing, for each
possible value, the number of pixels in the image
that have that particular value
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Multi-dimensional Histograms
• A multi-dimensional histogram is a function
of several variables
– For a color image, we can have a threedimensional histogram
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Point Operations and Histograms
• Point operations modifies the histogram in a
predictable way
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Applications of Point Operations
• Histogram equalization
– Find a point operation such that the histogram of
the resulting image will be a flat histogram
• Histogram matching
– Find a point operation such that the histogram of
the resulting image will match the one of a given
image
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Algebraic Operations
• Algebraic operations are operations that
produce an output image which is the pixelby-pixel sum, difference, product, quotient,
or other forms of functions of two input
images
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Traffic Estimation
• Suppose aerial photographs are taken of
highway section
– To estimate how many cars are there in the
section, find the difference between two
consecutive images and count the number of
white regions
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Blue-Screen Editing
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