在使用gdi技术画图时,有时会发现图形线条不够流畅,或者在改变窗口大小时会闪烁不断的现象.(Use DoubleBuffer to solve it!)
1.线条不流畅:窗口在重绘时自身重绘与图形重绘之间存在时间差,导致二者图像显示不协调
2.改变窗口大小不流畅:重绘时自身背景颜色与图形颜色频繁交替,造成视觉上的闪烁
以下,用四个图形样例解决问题 :贝塞尔曲线,圆形,矩形,不规则图形
思路:首先用Bitmap类的构造方法创建一个位图实例,然后通过调用Graphics类的FromImage方法创建画布对象,最后调用Grapgics类的DrawImage方法来实如今窗口上绘制图形.
public Bitmap(int width,int height); //width 定义位图的宽度 height 定义位图的高度
Bitmap lacalBitmap =new Bitmap(CilentRectangle.Width,CilentRectangle.Height); //创建一个与窗口工作区大小同样的位图实例
public static Graphics FromImage(Image image);// image:Image类的子类的实例引用
Bitmap localBitmap=new Bitmap(CilentRectangle.Width,CilentRectangle.Height) //创建位图实例
public void DrawImage(Image image,int x,int y); // image:要绘制的图像 x:绘制的图像的左上角 x坐标 y:左上角y坐标
Graphics g=e.Graphics;//获取窗口画布
g.DrawImage(localBitmap,0,0); //在窗口中绘制出内存中的图像
实现:因为Paint被 .net隐藏,我们须要在窗口代码中加上自己的Paint事件中绘制窗口
private void InitializeComponent()
{
this.SuspendLayout();
//
// Form1
//
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(388, 325);
this.MaximizeBox = false;
this.MinimizeBox = false;
this.Name = "Form1";
this.Text = "双缓冲技术画图";
this.Paint += new System.Windows.Forms.PaintEventHandler(this.Form1_Paint);
this.ResumeLayout(false);
}
this.Paint+=new System.Windows.Forms.PaintEventHandler(this.Form1_Paint);
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Drawing.Drawing2D; namespace DoubleBuffer
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
} private void Form1_Paint(object sender, PaintEventArgs e)
{
Bitmap localBitmap = new Bitmap(ClientRectangle.Width, ClientRectangle.Height);
//创建位图实例
Graphics bitmapGraphics = Graphics.FromImage(localBitmap);
bitmapGraphics.Clear(BackColor);
bitmapGraphics.SmoothingMode = SmoothingMode.AntiAlias;
PaintImage(bitmapGraphics);
Graphics g = e.Graphics;//获取窗口画布
g.DrawImage(localBitmap, 0, 0); //在窗口的画布中绘画出内存中的图像
bitmapGraphics.Dispose();
localBitmap.Dispose();
g.Dispose();
}
private void PaintImage(Graphics g)
{
//画图
GraphicsPath path = new GraphicsPath(new Point[]{ new Point(100,60),new Point(350,200),new Point(105,225),new Point(190,ClientRectangle.Bottom),
new Point(50,ClientRectangle.Bottom),new Point(50,180)}, new byte[]{
(byte)PathPointType.Start,
(byte)PathPointType.Bezier,
(byte)PathPointType.Bezier,
(byte)PathPointType.Bezier,
(byte)PathPointType.Line,
(byte)PathPointType.Line});
PathGradientBrush pgb = new PathGradientBrush(path);
pgb.SurroundColors = new Color[] { Color.Green, Color.Yellow, Color.Red, Color.Blue, Color.Orange, Color.LightBlue };
g.FillPath(pgb, path);
g.DrawString("双缓冲画图", new Font("宋体", 18, FontStyle.Bold), new SolidBrush(Color.Red), new PointF(110, 20));
g.DrawBeziers(new Pen(new SolidBrush(Color.Green),2),new Point[] {new Point(120,100),new Point(120,120),new Point(120,100),new Point(120,150)});
g.DrawArc(new Pen(new SolidBrush(Color.Blue), 5), new Rectangle(new Point(120, 170), new Size(60, 60)), 0, 360);
g.DrawRectangle(new Pen(new SolidBrush(Color.Orange), 3), new Rectangle(new Point(240, 260), new Size(90, 50)));
} }
}
Form1设计:
namespace DoubleBuffer
{
partial class Form1
{
/// <summary>
/// 必需的设计器变量。
/// </summary>
private System.ComponentModel.IContainer components = null; /// <summary>
/// 清理全部正在使用的资源。
/// </summary>
/// <param name="disposing">假设应释放托管资源，为 true；否则为 false。</param>
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
} #region Windows 窗口设计器生成的代码 /// <summary>
/// 设计器支持所需的方法 - 不要
/// 使用代码编辑器改动此方法的内容。
/// </summary>
private void InitializeComponent()
{
this.SuspendLayout();
//
// Form1
//
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 12F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(388, 325);
this.MaximizeBox = false;
this.MinimizeBox = false;
this.Name = "Form1";
this.Text = "双缓冲技术画图";
this.Paint += new System.Windows.Forms.PaintEventHandler(this.Form1_Paint);
this.ResumeLayout(false); } #endregion
}
}
Program.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms; namespace DoubleBuffer
{
static class Program
{
/// <summary>
/// 应用程序的主入口点。
/// </summary>
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
Application.Run(new Form1());
}
}
}
当变化窗口时,会导致图像出现变形,可把窗口属性中的ResizeReDrae 设置为 true
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