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POIs there an alpha value that makes white go invisible?
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copied!<p>If I use the following</p> <pre><code>for(int i = 255; i > 0; i--) { Color transparentBlack = new Color(0, 0, 0, i); } </code></pre> <p>I have the effect of the object using this color to draw with going from black to a light grey and then invisible when the alpha value goes to zero. However if I start with a white value:</p> <pre><code>new Color(255, 255, 255, i); </code></pre> <p>The objects never becomes invisible and only stays white. I've also noticed that if I use a value that is a bit lighter than black (say 50, 50, 50) the drawing goes from Dark, to invisible, to White.</p> <p>I assume that I just don't understand how alpha blending mixing works but is there a way of making a white color fade to translucency? </p> <p>Edit: The background I am drawing on is Color.CornflowerBlue (100,149,237,255)</p> <p>Edit: Sample XNA program reproducing the explanation. To use; create a new XNA Game Studio 4.0 project - Windows Game (4.0), call it AlphaBlendTest - & In the content project add a new SpriteFont and call it testfont </p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace AlphaBlendTest { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; SpriteFont font; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); font = Content.Load<SpriteFont>("testfont"); } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); // TODO: Add your update logic here base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); spriteBatch.Begin(); //spriteBatch.Draw(tR, new Rectangle(100, 100, 100, 100), Color.Red); Vector2 v2 = new Vector2(0, 0); spriteBatch.DrawString(font, "Test - White", v2, Color.White); v2.Y = v2.Y + 50; spriteBatch.DrawString(font, "Test - Black", v2, Color.Black); v2.Y = v2.Y + 50; Color BlackTransparent = new Color(0, 0, 0, 0); spriteBatch.DrawString(font, "Test - Black Transparent", v2, BlackTransparent); v2.Y = v2.Y + 50; Color WhiteTransparent = new Color(255, 255, 255, 0); spriteBatch.DrawString(font, "Test - White Transparent", v2, WhiteTransparent); spriteBatch.End(); base.Draw(gameTime); } } } </code></pre> <p>Edit: This is the image this code draws: <img src="https://i.stack.imgur.com/Y64zL.png" alt="alt text"></p> <p>Edit: One of the comments is concerned that this is a Text only related 'feature' of windows. I used text as an example to keep the demo program small; testing with an image gives the same result. <img src="https://i.stack.imgur.com/ibI7t.png" alt="alt text"></p> <p>To add the square box in to the demo program; create a square white PNG image and add it to the content directory (use the default values for the content pipeline). Then add this to the class:</p> <pre><code>Texture2D tWhiteBox; </code></pre> <p>Add this in to the load method:</p> <pre><code>tWhiteBox = Content.Load<Texture2D>("whitebox"); </code></pre> <p>Then in the draw add the following below the other draw statements:</p> <pre><code>v2.Y = v2.Y + 50; spriteBatch.Draw(tWhiteBox, v2, WhiteTransparent); </code></pre>

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