九、利用GDI+绘制文本

绘制文本在GDI+是非常广泛的应用。就像常见的验证码。在GDI+中使用DrawString

DrawString(String,Font,Brush,PointF)

DrawString(String,Font,Brush,RectangleF)

DrawString(String,Font,Brush,PointF,StringFormat)

DrawString(String,Font,Brush,RectangleF,StringFormat)

DrawString(String,Font,Brush,Single,Single)

DrawString(String,Font,Brush,Single,Single,StringFormat)

private void Form1_Paint(object sender, PaintEventArgs e)
{    
    //创建画板从Paint事件中的直接引用Graphics对象
    Graphics graphics = e.Graphics;

    graphics.Clear(Color.Black);

    //定义画笔
    Pen pen = new Pen(Color.White, 3.0f);
    Pen thickPen = new Pen(Color.White,2.0f);
    Pen thick = new Pen(Color.Red, 2.0f);

    //定义字体
    Font font = new Font("宋体",14);

    //定义画刷
    Brush brush = Brushes.Wheat;

    //定义位置
    Point point = new Point(100, 100);

    //定义点坐标
    graphics.DrawString("Hello", font, brush, point);

}

效果

下面开始做一个验证码的例子。后面逐渐会把验证码丰富起来，刚开始只是一个简单的。

private void Form1_Paint(object sender, PaintEventArgs e)
{    
    //创建画板从Paint事件中的直接引用Graphics对象
    Graphics graphics = e.Graphics;

    graphics.Clear(Color.Black);

    //验证码长度
    int intCheckCodeLength = 4;

    //先绘制一个现实验证码的区域    
    Rectangle rect = new Rectangle(200, 100, 220, 50);
    
    //填充的颜色
    Brush brushRect = Brushes.White;
    graphics.FillRectangle(brushRect, rect);    

    string[] strLetters = { "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z" };
    
    //字体名字    
    System.Drawing.Text.InstalledFontCollection fonts = new System.Drawing.Text.InstalledFontCollection();
    string[] sbFonts = { "Arial", "Arial Black", "Bauhaus 93", "Consolas", "Courier New" };    

    float floatOffset = 50;

    for (int i = 0; i < intCheckCodeLength;i++ )
    {
        Random rand = new Random(Guid.NewGuid().GetHashCode());
        int rndLetter = rand.Next(0, 26);
        int rndFont = rand.Next(0,sbFonts.Length-1);        

        Font font = new Font(sbFonts[rndFont].ToString(),32.0f);
        SolidBrush brush = new SolidBrush(Color.FromArgb(rand.Next(255),rand.Next(255),rand.Next(255)));
        graphics.DrawString(strLetters[rndLetter], font, brush, new PointF(205.0f+i*floatOffset, 100.0f));
    }
}