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Run my program

Click here to download a zip file containing my version of the program. Extract the folder named XNA0124Proj from the zip file and save it somewhere on your disk. Start Visual C# 2010 Express and select Open Project... from the File menu. Navigate to that folder and select the file with the extension of .sln . This should cause the project to open and be ready to run or debug as described in the earlier module titled Getting Started .


You learned about the following major topics in this module:

  • How to display a sprite in front of a background image.
  • The difference between the position and origin parameters of the SpriteBatch.Draw method.
  • How to cause the background image to change at runtime.
  • How to deal with and use color key transparency.


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Xna0124-Using Background Images and Color Key Transparency
  • File: Xna0124.htm
  • Published: 02/28/14

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I: I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

Complete program listing

A complete listing of the XNA program discussed in this module is provided in Listing 11 . Note the changes that were made in the calls to the SpriteBatch.Begin method to upgrade the program from XNA 3.1 to XNA 4.0. Blending was turned offin the first call just in case there were pixels in the background image having a color that matches the key color value.

Listing 11 . The class named Game1 for the project named XNA0124Proj.

/*Project XNA0124Proj * Illustrates displaying a sprite with color key* transparency in front of a background image. * Must modify the color key property value for the ufo* sprite, changing the key color from the default of * 255,0,255 (magenta or magic pink) to 0,255,0 (green).* The scale and the origin of the background image is * changed over time giving the illusion of a ufo* flying over a planet. ********************************************************/using System; using Microsoft.Xna.Framework;using Microsoft.Xna.Framework.Graphics; namespace XNA0124Proj {public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics;SpriteBatch spriteBatch; private Viewport viewport;private Vector2 ufoPosition; private float backgroundScale;private float backgroundBaseScale; private float dynamicScale = 0.0f;int msElapsed;//Time since last new frame. int msPerFrame = 83;//30 updates per secondTexture2D spaceTexture;//background image Texture2D ufoTexture;//ufo imageVector2 spaceOrigin;//origin for drawing background public Game1() {//constructorgraphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content";//Set the size of the game window, causing the // aspect ratio of the game window to match the// aspect ratio of the background image, which is // 640 wide by 480 high.graphics.PreferredBackBufferWidth = 450; graphics.PreferredBackBufferHeight =(int)(450.0*480/640); }//end constructor//-------------------------------------------------// protected override void Initialize() {// No initialization required base.Initialize();}//end Initialize //-------------------------------------------------//protected override void LoadContent() { // Create a new SpriteBatch, which can be used to// draw textures. spriteBatch = new SpriteBatch(GraphicsDevice);//Load the two images. spaceTexture = Content.Load<Texture2D>("space"); ufoTexture = Content.Load<Texture2D>("ufo"); //Get a reference to the viewport.viewport = graphics.GraphicsDevice.Viewport; //Compute the position of the ufo relative to the// game window. ufoPosition.X = viewport.Width / 2;ufoPosition.Y = viewport.Height - 70; //Set the backgroundBaseScale factor such that// the entire background image will fit in the // game window. Note that the aspect ratio of the// game window was set to match the aspect ratio // of the background image in the constructor.backgroundBaseScale = (float)(450.0 / 640.0); }//end LoadContent//-------------------------------------------------// protected override void UnloadContent() {// No unload required }//end UnloadContent//-------------------------------------------------// protected override void Update(GameTime gameTime) {//Compute the elapsed time since the last update. // Draw new data only if this time exceeds the// desired frame interval given by msPerFrame msElapsed += gameTime.ElapsedGameTime.Milliseconds;if(msElapsed>msPerFrame) { //Reset the elapsed time and draw the frame with// new data. msElapsed = 0;//Reset the animation if the dynamicScale factor // is greater than 10.if(dynamicScale>10) { dynamicScale = 0.0f;} else { //Increase the dynamicScale factor and use it// to compute a new scale factor that will be // applied to the background image in the next// call to the Draw method. dynamicScale += 0.03f;backgroundScale = backgroundBaseScale * (1 + dynamicScale);}//end if-else on dynamicScale //Also use the dynamicScale factor to compute a// new value for the origin of the background. // The origin is the point in the image that is// drawn at the point in the game window that is // passed as the second (position) parameter in// the call to the SpriteBatch.Draw method. This // has the effect of causing the background// image to slide up and to the left at the same // time that it is getting larger.spaceOrigin = new Vector2((float)(450 * (dynamicScale) / 12),(float)(338 * (dynamicScale) / 10)); }//end if on msElapsedbase.Update(gameTime); }//end Update//-------------------------------------------------// protected override void Draw(GameTime gameTime) {// Turn off blending to draw the planet in the // background. Note the update for XNA 4.0.// spriteBatch.Begin(SpriteBlendMode.None); spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.Opaque);//Draw the background. spriteBatch.Draw(spaceTexture,//spriteVector2.Zero,//position re window null,//rectangleColor.White,//tint 0,//rotationspaceOrigin,//origin backgroundScale,//scaleSpriteEffects.None, 1.0f);//layer, near the backspriteBatch.End(); // Turn on blending to draw the UFO in the// foreground. Note the update for XNA 4.0. // spriteBatch.Begin(SpriteBlendMode.AlphaBlend);spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend); //Center the UFO at the point in the window// identified as UFO position. The UFO image is // 64x33 pixels.Vector2 origin = new Vector2(32,16); spriteBatch.Draw(ufoTexture,//spriteufoPosition,//position re window null,//rectangleColor.White,//tine 0,//rotationorigin,//origin 1,//scaleSpriteEffects.None, 0f);//layer, 0 is in frontspriteBatch.End(); base.Draw(gameTime);}//end Draw method }//end class}//end namespace


Questions & Answers

How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
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