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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

An investment account was opened with an initial deposit of $9,600 and earns 7.4% interest, compounded continuously. How much will the account be worth after 15 years?
Kala Reply
lim x to infinity e^1-e^-1/log(1+x)
given eccentricity and a point find the equiation
Moses Reply
12, 17, 22.... 25th term
Alexandra Reply
12, 17, 22.... 25th term
College algebra is really hard?
Shirleen Reply
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find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
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how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
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okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
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Commplementary angles
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what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
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Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
Jeannette has $5 and $10 bills in her wallet. The number of fives is three more than six times the number of tens. Let t represent the number of tens. Write an expression for the number of fives.
August Reply
What is the expressiin for seven less than four times the number of nickels
Leonardo Reply
How do i figure this problem out.
how do you translate this in Algebraic Expressions
linda Reply
why surface tension is zero at critical temperature
I think if critical temperature denote high temperature then a liquid stats boils that time the water stats to evaporate so some moles of h2o to up and due to high temp the bonding break they have low density so it can be a reason
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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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