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DS420 Winter '99 |
Vivaldi |
Jorge H. Flores |
What is Image Processing?
The term digital image processing generally refers to the processing of pictures by a digital computer. Images are computer numerical representations of screens or pictures. A picture given in the form of a transparency, slide photograph, or chart is first digitized and then processed by a computer and/or classes of techniques. Examples of Image Processing tasks are : enhancement, restoration, compression and reconstruction (Fig 1). Image Recognition deals with image understanding and matching.
Figure 1.
Image Coding
Image coding reduces the storage requirement for an image by removing redundant information. This may be done in two ways: exact coding and fidelity coding.
Exact Coding
The image may be reconstructed exactly. Standard coding techniques may be used. Compression of 2:1 is typically achieved.
Fidelity Coding
The image may be reconstructed so that a human observer notices little or no degradation. Compression of 50:1 is typically achieved.
Some Applications of Image Coding
Image Enhancement
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
Image Restoration
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 degradation.
Image Segmentation
Sometimes similar areas in an image must be identified, for example from an aerial photograph the land and the sea may need to be segmented.
Feature Detection
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.
Applications of Image Restoration, Segmentation & Feature Detection.
