Image Processing Reference
In-Depth Information
Fig. 2.21
The
white
rectangle
defines a
region-of-interest (ROI), i.e.,
this part of the image is the
only one being processed
understanding optics requires a study on physics and how light interacts with the
physical world. A more easy way into these fields can be via the FCam [1], which
is a software platform for understanding and teaching different aspects of a camera.
Another way into these fields is to pick up a topic on Machine Vision. Here you
will often find a practical approach to understanding the camera and guidelines on
picking the right camera and optics. Such topics also contain practical information
on how to make your image/video analysis easier by introducing special lightning
etc.
While this chapter (and the rest of the topic) focused solely on images formed by
visual light it should be mentioned that other wavelengths from the electromagnetic
spectrum can also be converted into digital images and processed by the methods
in the following chapters. Two examples are X-ray images and thermographic im-
ages, see Fig.
2.22
. An X-ray image is formed by placing an object between an
X-ray emitter and an X-ray receiver. The receiver measures the energy level of the
X-rays at different positions. The energy level is proportional to the physical prop-
erties of the object, i.e., bones stop the X-rays while blood does not. Thermographic
images capture middle- or far-infrared rays. Heat is emitted from all objects via
such wavelengths meaning that the intensity in each pixel in a thermographic im-
age corresponds directly to the temperature of the observed object, see Fig.
2.22
.
Other types of image not directly based on the electromagnetic spectrum can also
be captured and processed and in general all 2D signals that can be measured can be
represented as an image. Examples are MR and CT images known from hospitals,
and 3D (or depth) images obtained by a laser scanner, a time-of-flight camera or the
Kinect sensor developed for gaming, see Fig.
2.22
.
