Question

我如何创建图形实例？我目前有这个：

public Graphics gameOverTextGFX = new Graphics;

但我收到错误：类型'System.Drawing.Graphics'没有定义构造函数

我尝试创建图形实例的原因是因为当我尝试渲染

时

gameOverTextGFX.DrawString("GAME OVER!", new Font("Arial", 24), Brushes.Red, 50f, 50f);

我收到异常：对象引用未设置为对象的实例。

我正在使用c＃和一个OpenGl，这不是在表单上，它在windows中我设置了一个大小等

GameOverScene.cs - 程序切换到这个场景很好，它只是不写线

using System;
using OpenTK;
using OpenTK.Graphics.OpenGL;
using OpenTK.Graphics;
using OpenTK.Input;
using System.Drawing;
using System.Drawing.Imaging;

namespace PongGame.Scenes
{
     class GameOverScene : Scene, IScene
    {
        public Bitmap gameOverTextBMP;
        public Graphics gameOverTextGFX;
        public GameOverScene(SceneManager sceneManager)
        : base(sceneManager)
    {
        // Set the title of the window
        sceneManager.Title = "Pong - Game Over";
        // Set the Render and Update delegates to the Update and Render methods of this class
        sceneManager.renderer = Render;
        sceneManager.updater = Update;
    }

    public void Update(FrameEventArgs e)
    {
    }

    public void Render(FrameEventArgs e)
    {
        gameOverTextGFX.DrawString("GAME OVER!", new Font("Arial", 24), Brushes.Red, 50f, 50f);
    }
}
}

我获得了一个正常工作的主菜单场景设置，但我试图将其应用于场景中的游戏，但它抛出了异常，说openGL线正在其他地方使用

public MainMenuScene(SceneManager sceneManager) : base(sceneManager)
    {
        // Set the title of the window
        sceneManager.Title = "Pong - Main Menu";
        // Set the Render and Update delegates to the Update and Render methods of this class
        sceneManager.renderer = Render;
        sceneManager.updater = Update;

        // Create Bitmap and OpenGL texture for rendering text
        textBMP = new Bitmap(sceneManager.Width, sceneManager.Height, System.Drawing.Imaging.PixelFormat.Format32bppArgb); // match window size
        textGFX = Graphics.FromImage(textBMP);
        textGFX.Clear(Color.CornflowerBlue);
        textGFX.Flush();
        textTexture = GL.GenTexture();
        GL.Enable(EnableCap.Texture2D);
        GL.BindTexture(TextureTarget.Texture2D, textTexture);
        GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)All.Linear);
        GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)All.Linear);
        GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, textBMP.Width, textBMP.Height, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, IntPtr.Zero);
        GL.BindTexture(TextureTarget.Texture2D, 0);
        GL.Disable(EnableCap.Texture2D);
    }

    public void Update(FrameEventArgs e)
    {
    }

    public void Render(FrameEventArgs e)
    {
        GL.Viewport(0, 0, sceneManager.Width, sceneManager.Height);
        GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);

        GL.MatrixMode(MatrixMode.Projection);
        GL.LoadIdentity();
        GL.Ortho(0, sceneManager.Width, 0, sceneManager.Height, -1, 1);

        if (textBMP != null)
        {
            textGFX.Clear(Color.CornflowerBlue);
            textGFX.DrawString("Hello", new Font("Arial", 20), Brushes.White, 0f, 0f);
            textGFX.DrawString("There", new Font("Arial", 20), Brushes.Red, 0f, 25f);

            // Enable the texture
            GL.Enable(EnableCap.Texture2D);
            GL.BindTexture(TextureTarget.Texture2D, textTexture);

            BitmapData data = textBMP.LockBits(new Rectangle(0, 0, textBMP.Width, textBMP.Height), ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppArgb);
            GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, (int)textBMP.Width, (int)textBMP.Height, 0, OpenTK.Graphics.OpenGL.PixelFormat.Bgra, PixelType.UnsignedByte, data.Scan0);
            textBMP.UnlockBits(data);

            GL.Begin(PrimitiveType.Quads);
            GL.TexCoord2(0f, 1f); GL.Vertex2(0f, 0f);
            GL.TexCoord2(1f, 1f); GL.Vertex2(sceneManager.Width, 0f);
            GL.TexCoord2(1f, 0f); GL.Vertex2(sceneManager.Width, sceneManager.Height);
            GL.TexCoord2(0f, 0f); GL.Vertex2(0f, sceneManager.Height);
            GL.End();

            GL.BindTexture(TextureTarget.Texture2D, 0);
            GL.Disable(EnableCap.Texture2D);
        }

Answer 1

为了制作新的Graphics对象，你需要从你想要绘制的控件的对象中调用CreateGraphics方法。

例如，如果您希望在Panel控件上绘图：

        Graphics MyGraph =  panel1.CreateGraphics();

Answer 2

要绘制到System.Drawing.Bitmap，请执行以下操作：

using( Graphics g = Graphics.FromImage( bitmap ) )
{
    // do painting with "g" here
}

处理（或使用using块）所有GDI类以防止内存泄漏非常重要。

创建System.Drawing.Graphics的实例

2 个答案: