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INTRODUCTION TO COMPUTER

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GRAPHICS Although graphics software was relative latecomer to the computer world, it has advanced a long way in a short time. In the early 1980, most graphics programs were limited to drawing simple geometric shapes, usually in black and white. Today, graphics software offers advanced drawing and painting tools, and virtually unlimited color control. In the newspapers and magazines, on posters and billboards. In TV and the movies can be subtle or stunning, obviously artificial, or amazingly lifelike.

Platforms In 1984, the introduction of the Apple Macintosh computer and a modest piece of software known as Mac Paint ushered in the era of “art” on the personal computer. With a pointing device and a black-and-white monitor that displayed images just as they would print, the Macintosh computer allowed users to Manipulate shapes, lines, and patterns with great flexibility. In the late 1980, Microsoft’s Windows brought many of the same capabilities to IBM PCs have achieved relative parity with Macintosh systems in the area of graphics software. A wide array of graphics programs is now available for both platforms.

Types of Graphics Files There are two basic groups into which these formats are divided: bitmap and vector formats.

Bitmaps Versus Vectors 

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A grid of dots, called a bitmap (Bitmap images are often referred to as raster images. Notes that, even though the two terms are interchangeable, this book uses the term bitmap, for consistency.) A set of vectors, which are mathematical equations describing the positions of lines. In general, graphics programs fall into two primary categories along this division. Those that work with bitmaps are called paint programs. Those that work with vectors are called draw programs. Each category has advantages and drawbacks, depending on the king of output needed. When you use bitmap-based graphics software, you are using the computer to move pixels around. If you look closely at a computer screen, you can see the tiny dots that make up images---these are pixels. Manipulating pixels can become complex. For example, an 8 * 10-inch black-and-white image---if displayed at a typical screen resolution of 72 pixels per inch (ppi)---is a mosaic of 414, 720 pixels. That means that the computer must remember he praise location of each and every one of those pixels as they are viewed, moved, or altered. If it is decided that the same 8 * 10-inch piece of artwork must have up to 256 colors in its makeup (which is considered minimal with today’s technology), then the computer must keep track of the 414,720 pixels multiplied by the 8 bits per pixel that are necessary to identify 256 different colors. That equals 3,317,760 bits that the computer must keep track of for one image. 1

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Unlike paint programs, which manipulate bitmaps, draw programs work their magic through mathematics. By using equations rather than dots to represent lines, shapes, and patterns, vector-based graphics software can represent highly detailed images with only a fraction of the computing power required by bitmaps. Strictly speaking, the vectors used by draw programs are lines drawn form point ot point. Vector-based software can use additional equations to define the thickness and color of a line, its pattern, and other attributes. Although a line on the screen is still displayed as a series of pixels (because that is how all computer screens work), to the computer it is an equation. Thus, to move the line from Point A to Point B, all the computer does is substitute the coordinates of Point A with hose for Point B. this saves the effort of calculating how to move thousands of individual pixels.

Standard File Formats If you need to share files with other users or move files between programs (artists and designers almost always do), you should be familiar with the standard file formats for graphics files, as shown in figure. These common formats apply only to bitmap images and can be used by nearly any newer software that creates or edits bitmap graphics.

Standard Formats for Bitmap Graphics FORMAT DESRIPTION BMP (BitMap) A graphics format native to Windows and the Windows applications created by Microsoft. Widely used on PCs, less so on Macs, although the Macintosh can read BMP files with programs such as Photoshop. PICT (PICTure) The native format defined by Apple for the Mac. Widely used on Macs but not PCs. TIFF (Tagged Image File Format) Bitmap format defined in 1986 by Microsoft and Aldus. Widely used on both Macs and PCs. JPEG (Joint Photographic Experts Group) A bitmap format common on the World Wide Web and often used for photos that will be viewed on screen JPEG is more than just a file format; it is a widely used standard that incorporates specific algorithms to ensure optimum image quality while keeping file size to a minimum. JPEG is often abbreviated as JPG. GIF (Graphic Interchange Format) A format developed by GomupServe. Like JPED images, GIF images are often found on World Wide Web pages. PNG (Portable Network Graphics) A format developed as an alternative to GIF. The PNG format is till emerging, but gaining popularity on World Wide Web pages. It provides greater color quality and more color attributes than GIF or TIFF files, but smaller file sizes than JPEG.

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Getting Existing Images into Your Computer The majority of graphics programs allow the user to create images form scratch, building simple lines and shapes into complex graphics. However, when using high-end graphics software, it is probably more common to begin with an existing image. If the image you start with is already a graphic file, then getting it into your computer is a matter of importing the file into the program that you want to use. Doing so simply requires that your program understand the file format in which the graphic is stored. There are, however, other building blocks with which you can start. The most common are clip art and printed images that you digitize (convert form a printed format to a digital one) using a scanner. If you do not have an image, you can use a digital camera to capture something in the real world quickly and import it into your computer.

Scanners and Digital Cameras A scanner is a little bit like a photocopy machine, except that instead of copying the image to paper, it transfers the images directly into the computer. If the image is on paper or a liked, a scanner can convert it into a digital file that a computer can manipulate. The scanner is attached to the computer by a cable and controlled by software that is often included with the graphics program. The result of scanning an image is a bitmap file (although software tools are available for translating these images into vector formats). Digital cameras are another way to import images into a computer. These devices store digitizes images in memory for transfer into a computer. Many are small and easy to use and include software and cables for the transfer process. Once again, the resulting file is generally bitmap

Electronic Photographs Today, graphic artists use traditional photos translated into digital formats more often than they use photos from digital cameras. Digitizing a photo always involves some type of scanner, but the process has become sophisticated in recent years. The PhotoCD offers many advantages. First, it provides a convenient storage medium of photos. Second, PhotoCD software makes it easy to quickly view and select photos from disk. Third, many PhotoCDs sore the images at several different resolutions, making them available for different purposes. (A magazine, for example, requires much higher-resolution images than a newspaper or a Web page.)

Clip Art The term “clip art” originated with the existence of large books filled with page after page of professionally created drawings and graphics that could be cut out, or clipped,“ from the pages and glued to a paper layout. Today, clip art is commonly available on CD-ROM, diskettes, or via commercial online services. Many word processing and presentation programs also feature a selection of clip art, although the choices may be limited unless the program

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came on a compact disk. Clip art can be found in both bitmap and vector formats.

GRAPHICS SOFTWARE Creating a digital image, or manipulating an existing one, can involve a huge variety of processes. No single piece of graphics software is capable of performing all the possible functions. In fact, there are five major categories of graphics software:  Paint software  Photo-manipulation software  Draw software  Computer-aided (CAD) software  3-D modeling and animation software Of the five, the first two are bitmap-based paint programs, and the rest are vector-based draw programs.

Paint Programs With software tools that have names like paintbrush, pen chalk, watercolors, airbrush, crayon, and eraser, paint programs have a familiar feel. However, because paint programs keep track of each and every pixel placed on a screen, they also can do things that are impossible with traditional artists’ tools---for example, erasing a single pixel or creating instant copies of an image.

Photo-Manipulation Programs When scanners made it easy to transfer photographs to the computer at high resolution, a new class of software was needed to manipulate these images on the screen. A cousin of paint programs, photo-manipulation programs now take the place of a photographer’s darkroom for many tasks. Although most often used for simple jobs such as sharpening focus or adjusting contrast, photomanipulation programs are also used to modify photographs in ways far beyond the scope of a traditional darkroom. Because photo-manipulation programs edit images at the pixel level, just as paint programs do, they can control precisely how a picture will look. They are also used to edit non-photographic images and to create images from scratch. The advent of photo-manipulation programs has caused an explosion in the use of computer to modify images. Adobe Photoshop, Corel Photo Paint, and Micrografx Picture Publisher are some popular photo-manipulation programs.

Draw Programs Draw programs are well suited for work where accuracy and flexibility are as important as coloring and special effects. Although they do not possess the pixelpushing capability of paint programs, they can be used to create images with an “arty” look and have been adopted by many designers as their primary tool. You see their output in everything from cereal box designs to television show credits, from business cards to newspapers. Macromedia Freehand, Adobe Illustrator, and CorelDraw are some popular draw programs.

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Draw programs offer two big advantages over paint programs first, when objects are created, they remain objects to the computer. After you draw a circle, you can return to it later and move it intact by dragging it with the mouse, even if it has been covered over with other shapes or lines. You can change the circle’s shape into an oval, or you can fill its interior with a color, a blend of colors, or a pattern. The other big advantage draw programs have is the capability to resize images easily so that they match the dimensions of the paper on which they will be printed. Because bitmap images are a grid of dots, the only way to control the size of the image is to adjust the resolution, the number of dots per inch. However, lowering the resolution to make an image larger can make the image visibly rougher.

3-D Modeling Programs Whether you are aware of it or not, you are constantly exposed to elaborate 3-D imaging in movies, television, and print. Many of these images are now created with a special type of graphics software called 3-D modeling software, which enables user to create electronic models of three-dimensional objects without using CAD software. Fast workstations or PCs coupled with 3-D modeling programs can lend realism to even the most fantastic subjects. Professional 3-D designers use sophisticated, expensive 3-D modeling programs such as 3-D Studio MAX, Electric Image, SoftImage, Rau Dream Designer, and Light-Wave 3D.

Animation An outgrowth of the 3-D explosion is computer-based animation. Since the creation of filmmaking, animation was possible only through a painstaking process of hand-drawing a series of images; and then filming them one by one. Each filmed image is called a frame. When the film is played back at high speed (usually around 30 frames per second for high-quality animation), the images blur together to create the illusion of motion on t he screens. The process of manually creating a short animation---even just a few second’ worth---can take weeks of labor. A five-minute cartoon or a feature-length animated movie can take months or even years to produce.

Graphics and the World Wide Web Perhaps even more than 3-D design and animation, the World Wide Web has aroused intense curiosity and interest in computer graphics. This is because nearly anyone can create and post a Web page, and the World Wide Web can supports many typed of graphics. Further, by using basic paint and draw software as described earlier in this chapter, it is easy to create or edit graphics for use on a Web page. Such graphics include simple items such as bullets and horizontal rules, more complicated images such as logos and complex artwork and photographs. If you have spent any time surfing he Web, you may agree that graphic elements truly enhance the viewing experience and can make even a simple page look elegant.

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Adding Graphics to a Web Page Although a Web page might look like one big graphic, remember that most pages are actually collections of graphics and text elements, combined by the browser according to HTML tags embedded in the page’s content. If any navigation buttons, icons, bullets, bars, or other graphics appear on the page, they are separate graphics files that are being displayed at the same time. When a Web page designer creates a Web page he or she usually begins by adding the text elements to an HTML-format file. By surrounding the text element with special codes----called HTML tags---the designer can cause different pieces of text to be displayed in different ways by the Web browser. Tags tell the Web browser what information to display and how to display it. The designer can also add tags that tell the browser to display graphics, and a single Web page can hold many individual graphics. On the Web server, the designer must store all the graphics files required by the Web page. When the user’s browser encounters the tags for a graphic, the server sends the graphic file to the browser. At the user’s end, the HTML tags help the browser organize the graphics, text, and other design elements on the page.

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