Image processing is used in a wide variety of applications, for two somewhat different purposes:
1. improving the visual appearance of images to a human observer, including their printing and transmission, and
2. preparing images for the measurement of the features and structures which they reveal.
The techniques that are appropriate for each of these tasks are not always the same, but there is considerable overlap. This book covers methods that are used for both tasks.
To do the best possible job, it is important to know about the uses to which the processed images will be put. For visual enhancement, this means having some familiarity with the human visual process and an appreciation of what cues the viewer responds to in images. A chapter on human vision addresses those issues. It also is useful to know about the printing or display process, since many images are processed in the context of reproduction or transmission. Printing technology for images has advanced significantly with the consumer impact of digital cameras, and up-to-date information is provided.
The measurement of images is often a principal method for acquiring scientific data and generally requires that features or structure be well defined, either by edges or unique brightness, color, texture, or some combination of these factors. The types of measurements that can be performed on entire scenes or on individual features are important in determining the appropriate processing steps. Several chapters deal with measurement in detail. Measurements of size, position, and brightness deal with topics that humans largely understand, although human vision is not quantitative and is easily fooled. Shape is a more difficult concept, and a separate chapter added in this edition summarizes a variety of ways that shape may be described by numbers. Measurement data may be used for classification or recognition of objects. There are several different strategies that can be applied, and examples are shown.