digital technology has made it possible to manipulate multi-dimensional
signals with systems that range from simple digital circuits to advanced
parallel computers. The goal of this manipulation can be divided into
Image Processing image in ->
Image Analysis image in ->
Image Understanding image in ->
high-level description out
will focus on the fundamental concepts of image processing.
Space does not permit us to make more than a few introductory remarks
about image analysis. Image understanding
requires an approach that differs fundamentally from the theme of this
book. Further, we will restrict ourselves to two-dimensional (2D) image
processing although most of the concepts and techniques that are to be
described can be extended easily to three or more dimensions. Readers
interested in either greater detail than presented here or in other
aspects of image processing are referred to
begin with certain basic definitions. An image defined in the "real
world" is considered to be a function of two real variables, for
example, a(x,y) with a as the amplitude
(e.g. brightness) of the image at the real coordinate position (x,y).
An image may be considered to contain sub-images sometimes referred to
as regions-of-interest, ROIs, or simply regions.
This concept reflects the fact that images frequently contain
collections of objects each of which can be the basis for a region. In a
sophisticated image processing system it should be possible to apply
specific image processing operations to selected regions. Thus one part
of an image (region) might be processed to suppress motion blur while
another part might be processed to improve color rendition.
amplitudes of a given image will almost always be either real numbers or
integer numbers. The latter is usually a result of a quantization
process that converts a continuous range (say, between 0 and 100%) to a
discrete number of levels. In certain image-forming processes, however,
the signal may involve photon counting which implies that the amplitude
would be inherently quantized. In other image forming procedures, such
as magnetic resonance imaging, the direct physical measurement yields a
complex number in the form of a real magnitude and a real phase. For the
remainder of this book we will consider amplitudes as reals or integers
unless otherwise indicated.