C# · 12月 22, 2021

c# – 是否存在使白色变为隐形的alpha值?

如果我使用以下内容 for(int i = 255; i > 0; i–){ Color transparentBlack = new Color(0,i);}

我有使用这种颜色的对象的效果,从黑色到浅灰色绘制,然后当alpha值变为零时不可见.但是,如果我以白色值开头:

new Color(255,255,i);

物体永远不会变得不可见,只会保持白色.我还注意到,如果我使用的值比黑色(比如50,50,50)轻一点,那么绘图就会从黑暗变为隐形,变为白色.

我假设我只是不明白alpha混合混合是如何工作的,但有没有办法使白色渐变为半透明?

编辑:我正在绘制的背景是Color.CornflowerBlue(100,149,237,255)

编辑:示例XNA程序再现说明.使用;创建一个新的XNA Game Studio 4.0项目 – Windows游戏(4.0),称之为AlphaBlendTest – &在内容项目中添加一个新的SpriteFont并将其命名为testfont

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),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”,Color.Black); v2.Y = v2.Y + 50; Color BlackTransparent = new Color(0,”Test – Black Transparent”,BlackTransparent); v2.Y = v2.Y + 50; Color WhiteTransparent = new Color(255,”Test – White Transparent”,WhiteTransparent); spriteBatch.End(); base.Draw(gameTime); }}}

编辑:这是此代码绘制的图像:

编辑:其中一条评论涉及这是一个仅与文本相关的Windows功能.我以文本为例来保持演示程序的小巧;使用图像进行测试会得到相同的结果.

将方框添加到演示程序中;创建一个方形白色PNG图像并将其添加到内容目录(使用内容管道的默认值).然后将其添加到类中:

Texture2D tWhite@R_855_2419@;

将其添加到load方法中:

tWhite@R_855_2419@ = Content.Load<Texture2D>(“white@R_855_2419@”);

然后在绘图中添加以下其他绘图语句:

v2.Y = v2.Y + 50;spriteBatch.Draw(tWhite@R_855_2419@,WhiteTransparent);解决方法 灰色是XNA 4.0中的颜色(如果您尝试仅调整Alpha通道而不调整RGB通道,则为全白色).使用预乘的alpha完成透明度(默认情况下).如果您正在寻找旧的非预先XNA 3.1行为,请参阅Shawn Hargreaves的这篇文章: http://blogs.msdn.com/b/shawnhar/archive/2010/04/08/premultiplied-alpha-in-xna-game-studio-4-0.aspx.在帖子的底部,它告诉你如何做到这一点.

我建议在这之前阅读他所有关于预乘alpha的帖子(你可以使用他页面顶部左侧的“Blog Index”链接) – pre-mul真的好多了在逻辑上更一致.