Chapter 6: Media and Document Integration
"The union of the mathematician with the poet, fervor with measure, passion with correctness, this surely is the ideal." -William James
The relationship between different media types such as graphics, video, and sounds with text in a document processing system is finicky. The integration of graphics, audio, and video with text into a complete electronic document is the source of many problems. This chapter examines these problems. In addition, we examine media formats and standards commonly used in electronic publishing. The decision about what media format to use has ramifications all along the document processing path, and we will also examine these. (The broader topic of compound documents is also discussed in Section 3 . 4 The Engineered View.)
As the increasing availability of high performance systems and Web browsers becomes ubiquitous, documents with many different types of media sometimes have problems. Media players, such as video or sound and graphics, are dependent on the execution of helper applications or more robust Web browsers. One terrific service by the folks at Lawrence Livermore Labs is a WWW Viewer Test Page.(1) On this page, they have compiled all the data types with a test button. When the test is selected, the Web server sends back data of the selected type. This is extremely useful for checking the functionality of a Web browser and its operating environment.
6 . 1 Bitmaps and Objects
Before we dive into text and graphics integration issues, let's examine some computer graphics fundamentals. There are two broad categories for representing graphic imagesbitmap and objectbased.
A bitmapped representation is the classic form used by "paint" systems. Each dot on the display screen corresponds to a bit of information in computer memory (hence the term bit, mapped). In contrast, objectbased systems (sometimes called geometric) are usually referred to as "draw" systems. Objectbased graphics use a geometric description to represent objects, such as lines, circles, and curves. These objects can be meaningfully manipulated as objects, not simply as dots on the screen. For example, to move a line, you can grab the end point and drag it to another place on the screen while the line stays intact; this is called rubber banding. The "paint" and "draw" distinctions originated with the success of MacPaint and MacDraw on the Macintosh, which use bitmap and objectbased representations, respectively.
Each approach has advantages and disadvantages. Using the bitmapped approach, you cannot select end points of lines or reshape curves. However, you can feather the edge of a shape into a soft blur or smoothly transition from one pastel shade to another. Painterly visuals such as soft edges and blurring are not practical when a system uses an objectbased approach. Image manipulations with functions such as edge detection and contrast enhancement also require a bitmap representation. Some graphics systems attempt to combine these two paradigms; however, the bitmap and object paradigms are the two fundamental representations of images.
The implementation and use of an objectbased representation for fonts was a key element in the desktop publishing revolution. Adobe's Type 1 font format allowed users virtually unlimited scaling of characters, while retaining the quality of the letterform. The object representation of the letterform is what produces this capability, along with the "hints" to maintain the quality of the strokes.(2) Jagged, blockylooking letters are the result of scaling the bitmap representation of a character.
