【教程】用VB.NET绘制GDI图形

用VB.NET绘制GDI图形例程

Protected Overrides Sub onpaint(ByVal e As System.Windows.Forms.PaintEventArgs)
【教程】用VB.NET绘制GDI图形
注释：/////////////绘制任意直线

Dim g As Graphics = e.Graphics

Dim mypen As Pen = New Pen(Color.Red, 2)

g.DrawLine(mypen, 100, 100, 10, 10)

注释：/////////////绘制矩形(任意直线构成的封闭图形)

Dim point1 As PointF = New PointF(100F, 100F)

Dim point2 As PointF = New PointF(200F, 100F)

Dim point3 As PointF = New PointF(200F, 200F)

Dim point4 As PointF = New PointF(100F, 200F)

Dim curvepoints As PointF() = {point1, point2, point3, point4}

g.DrawPolygon(New Pen(Color.Blue, 2), curvepoints)

注释：////////////文本表示

Dim FFamily As FontFamily = New FontFamily("Arial")

Dim font As Font = New Font(FFamily, "20", FontStyle.Bold, FontStyle.Italic,
GraphicsUnit.Pixel)

Dim text As String = "I love you!"

Dim solidbrush As SolidBrush = New SolidBrush(Color.Red)

Dim pr As PointF = New PointF(100, 10)

e.Graphics.DrawString(text, font, solidbrush, pr)

注释：////////////平面绘制

Dim rec As RectangleF = New RectangleF(10, 10, 200, 100)

g.DrawPie(mypen, rec, 150, 150)

注释：///////////封闭图形，0.7应该是个圆

g.DrawClosedCurve(mypen, curvepoints, 0.7,
Drawing.Drawing2D.FillMode.Alternate)

注释：///////////大家自己试试看吧

g.DrawArc(mypen, 300, 300, 200, 200, 100, 100)

g.DrawCurve(mypen, curvepoints)

g.DrawBezier(mypen, 50, 50, 100, 50, 100, 100, 50, 100)

g.DrawBeziers(mypen, curvepoints)

注释：//////////这可是一个圆

Dim rec1 As RectangleF = New RectangleF(10, 10, 100, 100)

g.DrawEllipse(mypen, rec1)

注释：//////////这是一个椭圆

Dim rec2 As RectangleF = New RectangleF(10, 10, 200, 100)

g.DrawEllipse(mypen, rec2)

End Sub

如果需要提高图片质量，把
image.Save(sDstFilePath, ImageFormat.Jpeg);
改成

这是提高质量后的效果：


附一些关键代码：

 GraphicsPath rectPath = CreateRoundRectanglePath(rect, image.Width / 10, sCornerLocation); //构建圆角外部路径
        Brush b = new SolidBrush(Color.White);//圆角背景白色
        g.DrawPath(new Pen(b), rectPath);
        g.FillPath(b, rectPath);
        g.Dispose();
        image.Save(sDstFilePath, ImageFormat.Jpeg);
        image.Dispose();
    }

    public static void CreatePlainText(string sSrcFilePath, string sDstFilePath,string sText, string sColor, string sSize, string sFont)
    {
        System.Drawing.Image image = System.Drawing.Image.FromFile(sSrcFilePath);
        Graphics g = Graphics.FromImage(image);
        g.SmoothingMode = SmoothingMode.AntiAlias;
        g.InterpolationMode = InterpolationMode.HighQualityBicubic;
        g.CompositingQuality = CompositingQuality.HighQuality;
        g.DrawImage(image, 0, 0, image.Width, image.Height);
        g.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias; //文字抗锯齿
        Font f = new Font(sFont,float.Parse(sSize));
        Brush b = new SolidBrush(ColorTranslator.FromHtml(sColor));
        Rectangle rect = new Rectangle(10, 5, image.Width, image.Height); //适当空开一段距离        
        for (int i = 0; i < 30; i++) //加强亮度
            g.DrawString(sText, f, b, rect);
        image.Save(sDstFilePath, ImageFormat.Jpeg);
        image.Dispose();
    }

    private static GraphicsPath CreateRoundRectanglePath(Rectangle rect, int radius, string sPosition)
    {
        GraphicsPath rectPath = new GraphicsPath();
        switch (sPosition)
        {
            case "TopLeft":
                {
                    rectPath.AddArc(rect.Left, rect.Top, radius * 2, radius * 2, 180, 90);
                    rectPath.AddLine(rect.Left, rect.Top, rect.Left, rect.Top + radius);
                    break;
                }

            case "TopRight":
                {
                    rectPath.AddArc(rect.Right - radius * 2, rect.Top, radius * 2, radius * 2, 270, 90);
                    rectPath.AddLine(rect.Right, rect.Top, rect.Right - radius, rect.Top);
                    break;
                }

            case "BottomLeft":
                {
                    rectPath.AddArc(rect.Left, rect.Bottom - radius * 2, radius * 2, radius * 2, 90, 90);
                    rectPath.AddLine(rect.Left, rect.Bottom - radius, rect.Left, rect.Bottom);
                    break;
                }

            case "BottomRight":
                {
                    rectPath.AddArc(rect.Right - radius * 2, rect.Bottom - radius * 2, radius * 2, radius * 2, 0, 90);
                    rectPath.AddLine(rect.Right - radius, rect.Bottom, rect.Right, rect.Bottom);
                    break;
                }
        }
        return rectPath;
    }
}

我再来详细解释一下刚才实现双缓冲的具体步骤：
1、 在内存中建立一块“虚拟画布”：
Bitmap bmp = new Bitmap(600, 600);
2、 获取这块内存画布的Graphics引用：
Graphics g = Graphics.FromImage(bmp);
3、 在这块内存画布上绘图：
g.FillEllipse(brush, i * 10, j * 10, 10, 10);
4、将内存画布画到窗口中
this.CreateGraphics().DrawImage(bmp, 0, 0);
总结
怎么样？是不是很简单？但是正是这个简单的操作大大提高了绘图效率，所以如果你需要进行GDI+图形编程，双缓冲技术一定要掌握，特别是在进行大量图形绘制刷新的情况下要尽量采用。

Rect *magnifier; //方形区域
GraphicsPath path; //放大镜圆周
Region *region;  //放大镜区域

magnifier=new Rect(point.x-100,point.y-100,200,200); //生成方形区域
path.AddEllipse(*magnifier); //根据方形区域生成圆周
region=new Region(&path); //构造放大镜区域

graphics->IntersectClip(region); //设置剪切区域
graphics->DrawImage(p_img,2*picRect.X-point.x,2*picRect.Y-point.y,2*picRect.Width,2*picRect.Height); //绘制放大镜区域图像

graphics->ReSetClip();
graphics->ExcludeClip(region);【教程】用VB.NET绘制GDI图形
graphics->DrawImage(p_img,picRect);  //绘制原图