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：
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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; }
}
/// <summary>
/// 绘制根据矩形旋转文本
/// </summary>
/// <param name="s">文本</param>
/// <param name="font">字体</param>
/// <param name="brush">填充</param>
/// <param name="layoutrectangle">局部矩形</param>
/// <param name="format">布局方式</param>
/// <param name="angle">角度</param>
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);
}
/// <summary>
/// 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
/// </summary>
/// <param name="s">文本</param>
/// <param name="font">字体</param>
/// <param name="brush">填充</param>
/// <param name="point">旋转点</param>
/// <param name="format">布局方式</param>
/// <param name="angle">角度</param>
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 < left)
left = pt.x;
if(pt.x > right)
right = pt.x;
if(pt.y < top)
top = pt.y;
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：
完整实例点此。
希望本文所述对大家的c#程序设计有所帮助
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