Image Processing Reference
In-Depth Information
even
fields. There is also an
aspect ratio
in picture transmission: pictures are arranged to
be 1.33 times longer than they are high. These factors are chosen to make television images
attractive to
human
vision, and can complicate the design of a framegrabber unit. Nowadays,
digital video cameras
can provide the digital output, in progressive scan (without interlacing).
Life just gets easier!
Aspect ratio
4
3
Television picture
Even field lines
Odd field lines
Figure 1.12
Interlacing in television pictures
This completes the material we need to cover for basic computer vision systems. For
more detail concerning practicalities of computer vision systems see, for example, Davies
(1994) and Baxes (1994).
1.4.3
Processing an image
Most image processing and computer vision techniques are implemented in computer
software
. Often, only the simplest techniques migrate to hardware; though coding techniques
to maximise efficiency in image transmission are of sufficient commercial interest that
they have warranted extensive, and very sophisticated, hardware development. The systems
include the Joint Photographic Expert Group (JPEG) and the Moving Picture Expert Group
(MPEG) image coding formats. C and C++
are by now the most popular languages for
vision system implementation: C because of its strengths in integrating high- and low-level
functions, and the availability of good compilers. As systems become more complex, C++
becomes more attractive when encapsulation and polymorphism may be exploited. Many
people now use Java as a development language partly due to platform independence, but
also due to ease in implementation (though some claim that speed/efficiency is not as good
as in C/C++). There is considerable implementation advantage associated with use of the
Java
TM
Advanced Imaging API (Application Programming Interface). There are some
textbooks that offer image processing systems implemented in these languages. Also, there
are many commercial packages available, though these are often limited to basic techniques,
and do not include the more sophisticated shape extraction techniques. The Khoros image
processing system has attracted much interest; this is a schematic (data-flow) image processing
system where a user links together chosen modules. This allows for better visualisation of
