C#利用GDI+绘制旋转文字等效果实例

2021-04-25 17:53

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本文实例讲述了C#利用GDI+绘制旋转文字等效果的方法，是非常实用的技巧。分享给大家供大家参考之用。具体如下：

C#中利用GDI+绘制旋转文本的文字，网上有很多资料，基本都使用矩阵旋转的方式实现。但基本都只提及按点旋转，若要实现在矩形范围内旋转文本，资料较少。经过琢磨，可以将矩形内旋转转化为按点旋转，不过需要经过不少的计算过程。利用下面的类可以实现该功能。

具体实现代码如下：

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
namespace RotateText
{
  public class GraphicsText
  {
    private Graphics _graphics;
    public GraphicsText()
    {
    }
    public Graphics Graphics
    {
      get { return _graphics; }
      set { _graphics = value; }
    }
    /// 
    /// 绘制根据矩形旋转文本
    /// 
    /// 文本
    /// 字体
    /// 填充
    /// 局部矩形
    /// 布局方式
    /// 角度
    public void DrawString(string s, Font font, Brush brush, RectangleF layoutRectangle, StringFormat format, float angle)
    {
      // 求取字符串大小
      SizeF size = _graphics.MeasureString(s, font);
      // 根据旋转角度，求取旋转后字符串大小
      SizeF sizeRotate = ConvertSize(size, angle);
      // 根据旋转后尺寸、布局矩形、布局方式计算文本旋转点
      PointF rotatePt = GetRotatePoint(sizeRotate, layoutRectangle, format);
      // 重设布局方式都为Center
      StringFormat newFormat = new StringFormat(format);
      newFormat.Alignment = StringAlignment.Center;
      newFormat.LineAlignment = StringAlignment.Center;
      // 绘制旋转后文本
      DrawString(s, font, brush, rotatePt, newFormat, angle);
    }
    /// 
    /// 绘制根据点旋转文本，一般旋转点给定位文本包围盒中心点
    /// 
    /// 文本
    /// 字体
    /// 填充
    /// 旋转点
    /// 布局方式
    /// 角度
    public void DrawString(string s, Font font, Brush brush, PointF point, StringFormat format, float angle)
    {
      // Save the matrix
      Matrix mtxSave = _graphics.Transform;
      Matrix mtxRotate = _graphics.Transform;
      mtxRotate.RotateAt(angle, point);
      _graphics.Transform = mtxRotate;
      _graphics.DrawString(s, font, brush, point, format);
      // Reset the matrix
      _graphics.Transform = mtxSave;
    }
    private SizeF ConvertSize(SizeF size, float angle)
    {
      Matrix matrix = new Matrix();
      matrix.Rotate(angle);
      // 旋转矩形四个顶点
      PointF[] pts = new PointF[4];
      pts[0].X = -size.Width / 2f;
      pts[0].Y = -size.Height / 2f;
      pts[1].X = -size.Width / 2f;
      pts[1].Y = size.Height / 2f;
      pts[2].X = size.Width / 2f;
      pts[2].Y = size.Height / 2f;
      pts[3].X = size.Width / 2f;
      pts[3].Y = -size.Height / 2f;
      matrix.TransformPoints(pts);
      // 求取四个顶点的包围盒
      float left = float.MaxValue;
      float right = float.MinValue;
      float top = float.MaxValue;
      float bottom = float.MinValue;
      foreach(PointF pt in pts)
      {
        // 求取并集
        if(pt.X  right)
          right = pt.X;
        if(pt.Y  bottom)
          bottom = pt.Y;
      }
      SizeF result = new SizeF(right - left, bottom - top);
      return result;
    }
    private PointF GetRotatePoint(SizeF size, RectangleF layoutRectangle, StringFormat format)
    {
      PointF pt = new PointF();
      switch (format.Alignment)
      {
        case StringAlignment.Near:
          pt.X = layoutRectangle.Left + size.Width / 2f;
          break;
        case StringAlignment.Center:
          pt.X = (layoutRectangle.Left + layoutRectangle.Right) / 2f;
          break;
        case StringAlignment.Far:
          pt.X = layoutRectangle.Right - size.Width / 2f;
          break;
        default:
          break;
      }
      switch (format.LineAlignment)
      {
        case StringAlignment.Near:
          pt.Y = layoutRectangle.Top + size.Height / 2f;
          break;
        case StringAlignment.Center:
          pt.Y = (layoutRectangle.Top + layoutRectangle.Bottom) / 2f;
          break;
        case StringAlignment.Far:
          pt.Y = layoutRectangle.Bottom - size.Height / 2f;
          break;
        default:
          break;
      }
      return pt;
    }
  }
}

测试代码如下：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Windows.Forms;
namespace RotateText
{
  public partial class FormMain : Form
  {
    private Font _font = new Font("Arial", 12);
    private Brush _brush = new SolidBrush(Color.Black);
    private Pen _pen = new Pen(Color.Black, 1f);
    private string _text = "Crow Soft";
    public FormMain()
    {
      InitializeComponent();
    }
    protected override void OnPaint(PaintEventArgs e)
    {
      base.OnPaint(e);
      GraphicsText graphicsText = new GraphicsText();
      graphicsText.Graphics = e.Graphics;
      // 绘制围绕点旋转的文本
      StringFormat format = new StringFormat();
      format.Alignment = StringAlignment.Center;
      format.LineAlignment = StringAlignment.Center;
      graphicsText.DrawString(_text, _font, _brush, new PointF(100, 80), format, 45f);
      graphicsText.DrawString(_text, _font, _brush, new PointF(200, 80), format, -45f);
      graphicsText.DrawString(_text, _font, _brush, new PointF(300, 80), format, 90f);
      graphicsText.DrawString(_text, _font, _brush, new PointF(400, 80), format, -60f);
      // 绘制矩形内旋转的文本
      // First line
      RectangleF rc = RectangleF.FromLTRB(50, 150, 200, 230);
      RectangleF rect = rc;
      format.Alignment = StringAlignment.Near;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 30);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Near;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, -30);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Center;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, -90);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Far;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 70);
      // Second line
      rect = rc;
      rect.Location += new SizeF(0, 100);
      format.Alignment = StringAlignment.Center;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 40);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Near;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 30);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Center;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, -70);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Far;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 60);
      // Third line
      rect = rc;
      rect.Location += new SizeF(0, 200);
      format.Alignment = StringAlignment.Far;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, -30);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Near;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, -30);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Center;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 90);
      rect.Location += new SizeF(180, 0);
      format.LineAlignment = StringAlignment.Far;
      e.Graphics.DrawRectangle(_pen, rect.Left, rect.Top, rect.Width, rect.Height);
      graphicsText.DrawString(_text, _font, _brush, rect, format, 45);
    }
  }
}

效果如下图：

技术分享图片