What is an Image?
- A Two Dimensional Data Structure made up from picture
What is Image Processing?
- Performing operations on images.
- Large amount of data (~1 million numbers for a high quality
- Pixels are related to their neighbours.
- Most of the data is redundant (i.e. it contains little
Image Processing Characteristics
- Many Simple Operations.
- It is only recently that sufficient processing power
has become available; users may now perform image processing on relatively
- A working model is available:
The Human Visual System.
Image Processing Operations
Image coding reduces the storage requirement for an image
by removing redundant information. This may be done in two ways.
The image may be reconstructed exactly. Standard coding
techniques may be used.
Compression of 2:1 is typically achieved.
- The image may be reconstructed so that a human observer
notices little or no degradation.
Compression of 50:1 is typically achieved.
Applications of Image Coding
- Digital Cameras.
- CDROM MPEG Movies.
- Video on Demand.
- Hypermedia Documents.
An image may need to be processed so that it may be viewed.
For example, an X-ray image may be displayed with greater contrast in some
regions so that very faint features can be seen.
Applications of Image Enhancement
- Medical Imaging.
- Scientific Visualisation.
- Particle Physics.
If an image has known faults then these may often be corrected.
A blurred image may be 'deblurred' or a noisy image may have noise removed.
Restoration often relies on knowledge of the process that caused the degradation.
Noise removal applied once
Noise Removal applied twice
Sometimes similar areas in an image must be identified,
for example from an aerial photograph the land and the sea may need to
Often, only part of an image is of interest.
Feature detection creates an image that contains information
about the presence of certain types of features. Edges are common features.
Edges in Image
Feature Detection using the Hough Transform
Image of Road
Hough Transform of Road Image
Applications of Image Restoration, Segmentation and Feature
- Remote Sensing.
- Medical Imaging.
- Character Recognition.
- Data Analysis.
- Computational Vision.
- Feature Location.
- Gesture recognition.