David Salomon

The Computer Graphics Manual

This book presents a broad overview of computer graphics (CG), its history, and the hardware tools it employs. Covering a substantial number of concepts and algorithms, the text describes the techniques, approaches, and algorithms at the core of this field. Emphasis is placed on practical design and implementation, highlighting how graphics software works, and explaining how current CG can generate and display realistic-looking objects. The mathematics is non-rigorous, with the necessary mathematical background introduced in the Appendixes. Features: includes numerous figures, examples and solved exercises; discusses the key 2D and 3D transformations, and the main types of projections; presents an extensive selection of methods, algorithms, and techniques; examines advanced techniques in CG, including the nature and properties of light and color, graphics standards and file formats, and fractals; explores the principles of image compression; describes the important input/output graphics devices.

Privacy and Trust

In this age of computers, the Internet, and massive data bases that never lose or forget anything, it is no wonder that we feel we are losing our privacy and we get very concerned about it. The reason for this loss can be found in the phrase “once something is released into the Internet, it can never be completely deleted.” We give away bits and pieces of personal information all the time, but we give them to different entities, at different times, and through different media such as paper or verbally. We therefore expect these pieces of information to disappear or at least to stay separate. The nature of the online world, however, is such that individual pieces of information tend to gravitate toward one another and coalesce into solid objects called personal records.

B-Spline Approximation

This is the second volume of A Manual of Computer Graphics. This textbook/reference is big because the discipline of computer graphics is big. There are simply many topics, techniques, and algorithms to discuss, explain, and illustrate by examples. Because of the large number of pages, the book has been produced in two volumes. However, this division of the book into volumes is only technical and the book should be considered a single unit.

Examples of Malware

The history and main features of several computer viruses and worms are described in this chapter. More examples can be found in Appendix C. Due to the prevalence of rogue software, there are many similar descriptions on the Internet. Notice that most of the examples are from the 1980s and 1990s, because this was the time when new, original, and very destructive malware appeared regularly and caused great alarm and much harm to computer users worldwide.

Data Hiding in Images

Virtually all sophisticated steganographic methods hide a message by embedding it as low-level noise in an image or audio file which then becomes the cover file. This approach has two disadvantages: the information hiding capacity of a cover file is small, so a large cover file is needed to hide a substantial amount of data; and once data are hidden in an image or audio file, any lossy compression destroys the embedded data. It seems that such an image should be compressed with lossless compression only, but this chapter shows how secret data can be hidden even in a lossily compressed image.

Data Hiding in Text

Today, in the digital age, any type of data, such as text, images, and audio, can be digitized, stored indefinitely, and transmitted at high speeds. Notwithstanding these advantages, digital data also have a downside. They are easy to access illegally, tamper with, and copy for purposes of copyright violation.

Public-Key Cryptography

The problem of key distribution has been mentioned many times in this book. For many years it was strongly believed that this problem has no satisfactory solution, but in the 1970s, an ideal, simple solution was found and has since become the foundation upon which much of modern cryptography is based.

The ASCII Code

Table A.l shows the 128 ASCII codes. Each code is shown in octal (leftmost column and top row) and hexadecimal (rightmost column and either the top or bottom rows). Octal numbers are typeset in italics, preceded by a quote (’). Hex numbers are typeset in a fixed-width font, preceded by a double-quote (′′). To find the code of a character, substitute the code from the top or bottom row for the x. The octal code of “A,” e.g., is found by substituting the ’1 from the top row for the x in the ′10x from the left column, i.e., it is octal 101 or binary 1000001. Similarly, the hex code of “A” is a combination of ′′4x and ′1 , i.e., it is ′′41.

Visible Surface Determination

We are surrounded by objects of every size, shape, and color, but we don’t see all of them. Nearby objects tend to obscure parts of distant objects. The visibility problem, the problem of deciding which elements of a rendered scene are visible by a given observer, and which are hidden, has to be solved by any three-dimensional graphics program or software package.

The Wavelet Transform

The concept of a transform was introduced in Section 24.1 and the rest of Chapter 24 discusses orthogonal transforms. The transforms dealt with in this chapter are different and are referred to as subband transforms, because they partition an image into various bands or regions that contain different features of the image.