Basics of Computer Graphics

OCEAN COUNTY VOCATIONAL TECHNICAL SCHOOL • GRAPHIC DESIGN TECHNOLOGY PROGRAM

Basics of Computer Graphics & File Formats

Read the following reference material on "Computer Graphics". Use it to help you complete the "Basics of Computer Graphics" Review Questions sheet that your instructor distributed in class.

BE CERTAIN TO READ ALL INFORMATION CAREFULLY AS YOU WILL BE TESTED ON ALL MATERIAL COVERED IN THIS SECTION.

Before the student can begin to create and manage computer graphic files, there is some basic theory and some file format information that should be reviewed. The following information concerns graphic files, but some file format issues pertain to computer files in general.

What are computer graphics?

The term "computer graphics" is derived from two other extremely important terms. It is understood that most students are by now familiar with what a "computer" is, and what we can accomplish by using it as a tool. "Graphics" is a little more difficult to comprehend, since it is used to describe many things. "Graphic Art" is a widely used term, describing the technology behind printing and the preparing of artwork before it can be printed. "Graphics" is also used to describe illustrations, when used in conjunction with printed or computer generated words or "type".

Graphics help us communicate ideas or information.

One of the earliest means of communication for man was through the use of pictures. If people were unable to understand the message being relayed, signs or pictures helped in communication. Early cave paintings are examples of "graphic communication". This is also referred to as "visual communication". People still use this universal way to communicate, for instance, during the Olympic Games. Universal symbols direct people to food, lodging, and transportation. Therefore, "visual communication" and "graphics" are one of the earliest forms of communication.

Computers represent the latest technology for communicating with others.

In its earliest stages of development, only scientists and engineers had access to computers. Today, many teens will return home from school, where they will communicate with friends and access information from their own "personal computer". The growth of the "personal computer" industry has branched out into many professional areas. One area where the impact of computers has been tremendous is in the area of the "graphic art" and "publishing" industries. New technology enables us to convert pictures and words into electronic sound pulses and transmit them through phone lines and satellites to the farthest corners of the earth. This is a far cry from cave paintings. Yet, when we look at what we are doing, we are just using a new tool to enable us to visually communicate with each other.

I've got a computer, can I create "computer graphics"?

Computers were not always able to do "graphics". In the beginning, computers could only handle letters or "characters" similar to a typewriter. Lines and graphics were composed of smaller lines and symbols to create crude pictures.

The early monitors were green or amber with lighter colored letters and characters. In order to see how your image would look on paper, you had to print it out. Then "WYSIWYG" (pronounced wizzywig) displays were developed. That stands for "what you see is what you get". These monitors were white with black letters so that they looked like what would print out on paper. But the image was still not as good as graphic artists needed and it had nothing to do with the monitor or the equipment. There was no professional way to create graphics, without the proper programs or "software".

So if I buy the right "software", then I can do computer graphics"?

Now we are getting down to the important issue that enables graphic artists to create computer graphics. The development of specialized computer programs or "software" has allowed us to create computer graphics, but only with the improvement of the computer parts themselves or the computer "hardware". The complicated part of the issue is that different programs create and handle graphics differently. There are two basic types of "computer graphics" and the graphic artist must be aware of how each one works and is important to the work that they do.

Why do there have to be two kinds of "computer graphics"?

As computer graphics evolved, the latest available technology was used in order to create the best image. Initially, computers handled graphics as we discussed earlier. Then technology enabled the artist to compose pictures of small squares or rectangles. The squares are called "pixels" (short for "picture elements"). These were grouped together in shapes to form our first true computer graphics. These picture elements could also be shaped to form letters. These first computer graphics were called "bitmap" graphics. The letters were called "bitmap fonts". The drawback to this type of graphic was that the early ones were very blocky or jagged looking. Lines on an angle resembled a staircase. Needless to say, they were not perfect, but they worked. The biggest drawback to these graphics and "fonts" (styles of different letters), was the amount of space that they take up in memory. That remains a problem to this day. In order for the image to get sharper, the dots must be smaller and the amount of dots must be larger. This sharpness of the "pixels" is referred to as "resolution". This is one of the most important concepts to develop in the area of "digital imaging" and "digital" photography.

If "bitmap graphics" are so old, then why do we have to know about them?

"Scanners" and "digital cameras" rely on bitmapping technology in order to "digitize" images. This means that scanners and digital cameras create an image by breaking it into "pixels" and then storing that information on a disk or on the monitor of the computer. "Resolution" is the method of measuring the quality and clarity of a digital image. "Higher resolution" usually is seen on more expensive scanners and digital cameras. This means that you will be able to capture clearer images. That does not necessarily mean that you will be able to print better pictures if you get a better scanner or digital camera. Printing is still dependent on the "resolution" of your printer. This is a discussion that should continue when you have understood the basics, but you must understand that bitmapped graphics will be around for some time to come.

What other type of graphics are there?

The other type of graphic that is widely used is called "vector graphics". Due to the nature of bitmapped graphics, it is difficult to image diagonal and curved lines without getting a stair-stepped look. This is Sometimes referred to as "jaggies". "Vector graphics" are able to create perfectly smooth diagonal and curved lines and shapes. This is accomplished by the way that the image is created by the computer. "Bitmapped graphics" create an image through a group of squares which is mapped out in a grid on a page. "Vector graphics" use algebraic formulas to plot out points on a line. These points are then used to create the image.

What are "vector graphics" used for?

"Vector graphics" are used in "Computer Assisted Design" (CAD) programs for drafting and also in powerful illustration programs for creating smooth geometric shapes for "logo" design and complex illustrations that are not possible when using "bitmapped" programs. However, the primary impact of "vector graphics" has been in the area of type. Bitmapped type fonts used to take up a tremendous amount of storage space and could be jagged when enlarged. Vector based type allows for incredible enlargements of type (letters) without any loss of quality at all. This is called "scalable type".

How can I tell bitmap graphics from vector graphics?

Sometimes it is difficult, if not impossible to tell a bitmap image from a vector image. Beginners must become familiar with file formats and file name extensions. That is the easiest way to tell them apart. There are many different file formats. Some of them are listed in the table below. Try to become familiar with them, as you will be using many of these and will be tested on them.

File Format Name	Extension	Type	Use
CorelDraw	.cdr	vector	Corel vector graphics
Adobe Photoshop	.psd	bitmap	Photos, bitmap graphics
Quark Xpress	.qxd	vector	Quark Xpress documents
Tag Image File Format	.tif	bitmap	photos, scanned graphics, bitmap graphics
Graphic Interchange Format	.gif	bitmap	bitmap graphics, web graphics
Joint Photographic Experts Group	.jpg	bitmap	photos, bitmap graphics, web graphics
Windows Bitmap	.bmp	bitmap	photos, bitmap graphics
Encapsulated Postscript	.eps	vector / bitmap	both vector graphics and bitmap photos (metafile)
Windows Metafile	.wmf	vector / bitmap	vector graphics
Text File	.txt	ASCII / ANSI	text file format

This chart only scratches the surface of file formats. There are many "proprietary" formats. That means that the file may only be opened by the program that created it. For example, a Corel DRAW file can only be opened in Corel DRAW. However, files may also be "imported" and "exported" in certain programs. That topic will be discussed on the web page entitled "Importing and Exporting Graphic Files".

When you have completed reviewing this material and have completed the review questions, you may wish to read it over again. There will be a test on this material.

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