Home > Articles

Learning to Draw Basic Graphics

  • Print
  • + Share This
This chapter is from the book

This chapter is from the book

NOTE

1979 was a critical milestone in the evolution of video games because it brought us Asteroids, which is one of the most enduring games ever. Created by Atari, Asteroids was one of the first vector graphics games, which means that it relied solely on lines to draw graphics, as opposed to little square pixels. Asteroids demonstrated that a very simple concept, with even simpler graphics and a soundtrack that gradually builds tension, creates a mix for success. In fact, Asteroids was so successful that arcade operators had to build larger coin boxes for the games—not a bad problem to have!

A computer game consists of many different pieces, all of which must come together to form a unique entertainment experience for the player. By far, the most important pieces of any game are the graphics. Graphics are used to represent the characters and creatures in a game, as well as background worlds and other interesting objects that factor into the overall game design. Granted, games have certainly done well because of factors outside of graphics, such as game play and sound quality, but those games are very rare. Besides, nowadays game players expect to see high-quality graphics just as we all expect to see high-quality visual effects in Hollywood movies. So, it's important to develop a solid understanding of graphics programming and how to use graphics wisely in your games.

In this chapter, you'll learn

  • The basics of drawing graphics using the Windows Graphics Device Interface

  • What a device context is and why it's important to GDI graphics

  • How to paint text and primitive graphics in Windows

  • How to create a sample program that demonstrates GDI graphics in the context of the game engine

Graphics Essentials

Before jumping into the details of how graphics work in Windows and how they are applied to games, it's important to establish some ground rules and gain an understanding of how computer graphics work in general. More specifically, you need to have a solid grasp on what a graphics coordinate system is, as well as how color is represented in computer graphics. The next couple of sections provide you with this knowledge, which you'll put to practical use a little later in the chapter.

Understanding the Graphics Coordinate System

All graphical computing systems use some sort of graphics coordinate system to specify how points are arranged in a window or on the screen. Graphics coordinate systems typically spell out the origin (0, 0) of the system, as well as the axes and directions of increasing value for each of the axes. If you're not a big math person, this simply means that a coordinate system describes how to pinpoint any location on the screen as an XY value. The traditional mathematical coordinate system familiar to most of us is shown in Figure 3.1.

Figure 3.1Figure 3.1 The traditional XY coordinate system is commonly used in math.

Windows graphics relies on a similar coordinate system to specify how and where drawing operations take place. Because all drawing in Windows takes place within the confines of a window, the Windows coordinate system is applied relative to a particular window. The Windows coordinate system has an origin that is located in the upper-left corner of the window, with positive X values increasing to the right and positive Y values increasing down. All values in the Windows coordinate system are positive integers. Figure 3.2 shows how this coordinate system looks.

Figure 3.2Figure 3.2 The Windows XY coordinate system is similar to the traditional coordinate system except that it applies to the client area of windows.

NOTE

When I talk about drawing graphics in a window, I'm actually referring to the client area of a window, which doesn't include the title bar, menus, scrollbars, and so on. In the case of games, you can think of the client area of the main game window as the game screen. You learn more about the client area of a window later in this chapter in the section titled, "Painting Windows."

If the Windows graphics coordinate system sounds a little complicated, just think of it in terms of a classic game of Battleship. In Battleship, you try to sink enemy ships by firing torpedoes at specific locations on a grid. Battleship uses its own coordinate system to allow you to specify locations on the grid where ships might be located. Similarly, when you draw graphics in Windows, you specify locations in the client area of a window, which is really just a grid of little squares called pixels.

Learning the Basics of Color

A topic that impacts almost every area of game graphics is color. Fortunately, most computer systems take a similar approach to representing color. The main function of color in a computer system is to accurately reflect the physical nature of color within the confines of a computer. This physical nature isn't hard to figure out; anyone who has experienced the joy of Play-Doh can tell you that colors react in different ways when they are combined with each other. Like Play-Doh, a computer color system needs to be capable of mixing colors with accurate, predictable results.

Color computer monitors provide possibly the most useful insight into how software systems implement color. A color monitor has three electron guns: red, green, and blue. The output from these three guns converges on each pixel on the screen, stimulating phosphors to produce the appropriate color. The combined intensities of each gun determine the resulting pixel color. This convergence of different colors from the monitor guns is very similar to the convergence of different colored Play-Doh.

NOTE

Technically speaking, the result of combining colors on a monitor is different from that of combining similarly colored Play-Doh. The reason for this is that color combinations on a monitor are additive, meaning that mixed colors are added together to become white; Play-Doh color combinations are subtractive, meaning that mixed colors are subtracted from each other to become black. Whether the color combination is additive or subtractive depends on the physical properties of the particular medium involved.

The Windows color system is very similar to the physical system used by color monitors; it forms unique colors by using varying intensities of the colors red, green, and blue. Therefore, Windows colors are represented by the combination of the numeric intensities of the primary colors (red, green, and blue). This color system is known as RGB (Red Green Blue) and is standard across most graphical computer systems.

NOTE

RGB isn't the only color system used by computers. Another color system used heavily in desktop publishing applications is CMYK, which stands for Cyan-Magenta-Yellow-Black. Colors in the CMYK color system are expressed in terms of the color components cyan, magenta, yellow, and black, as opposed to red, green, and blue in RGB. The CMYK color system is used heavily in printing because CMYK printing inks are subtractive in nature, making it easier to print using a four-color ink combination (cyan, magenta, yellow, and black); hence the term four-color printing.

Table 3.1 shows the numeric values for the red, green, and blue components of some basic colors. Notice that the intensities of each color component range from 0 to 255 in value.

Table 3.1 Numeric RGB Color Component Values for Commonly Used Colors

Color

Red

Green

Blue

White

255

255

255

Black

0

0

0

Light Gray

192

192

192

Medium Gray

128

128

128

Dark Gray

64

64

64

Red

255

0

0

Green

0

255

0

Blue

0

0

255

Yellow

255

255

0

Purple

255

0

255


The Win32 API defines a structure named COLORREF that combines the red, green, and blue components of an RGB color into a single value. The COLORREF structure is important because it is used throughout the Win32 API to represent RGB colors. To create a color as a COLORREF structure, you use the RGB() macro, which accepts red, green, and blue color components as arguments. Here is an example of creating a solid green color using RGB():

COLORREF green = RGB(0, 255, 0);

The color created in this line of code is green because the green component (the middle argument) is specified as 255, whereas the red and blue components are specified as 0. Changing the values of these three arguments alters the mix of the color—with lower numbers resulting in darker colors and higher numbers resulting in brighter colors.

You can experiment with RGB color combinations in the standard Paint program that comes with Windows. Double-click one of the colors in the color palette in the lower left corner of the Paint window. Then, click the Define Custom Colors button in the Edit Colors dialog box. You can then either type numbers into the Red, Green, and Blue edit fields or click to select a color and intensity (see Figure 3.3).

Figure 3.3Figure 3.3 The standard Windows Paint program allows you to specify colors via RGB values.




  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020