OpenGl下可以方便的操作字符,但是对字符串显示的支持不够.OpenGL本身不提供文字的显示和处理能力,如要显示文字的借助于第三方的扩展程序。初涉OpenGl, 想请教有什么好的方法可以解决这个问题?网上觅得bluebohe三年前的一篇文章, 在vs2005下实现他的代码, 编译通过了, 但是结果显示不出来. 可否帮忙看看? COpenGLText源码
bluebohe的原文:
一直以来,OpenGL状态下的文字显示都是一个问题,本文使用嵌套显示列表的方式进行OpenGL状态下的字符串的显示。
有以下几点需要注意:
1:本程序显示按照给定的高度和文字的位置显示某一种字体的文字,其中一些字体的参数定义在OpenGLText内部给定,可以随意将它抽出来。如果将代码用于实际应用中,建议文字的文字间距自己设定,也可以随意添加文字的倾斜角、旋转角度、定位方式等等参数。
2:wglUseFontOutlines函数的第五个参数表示文字的精度(弦偏差),一般设置成零,但这样缺省的做法会导致文字太粗糙,可以将它设置成一个比较小的数,以提高文字显示的精确度,但这样会增加内存的占用量。
3:如果文字的高度比较小,文字的线条可能会出现断裂的现象,影响美观,解决这类问题有以下几种方式:(1)使用OpenGL反走样技术;(2)把文字的轮廓用线条勾勒出来;(3)在文字的Draw成员函数中多次调用glCallList函数,每次调用向周围平移一个像素,这样的话会使文字的线条断裂问题大为改观,速度也是三种方式中最快的。
应用方式如下:
COpenGLText text;
COpenGLText text2;
text2.m_dX=0;
text2.m_dY=200;
glLoadIdentity();
glClear(GL_COLOR_BUFFER_BIT);
glColor4f(0.0f, 0.0f, 1.0f, 1.0f);
text.Draw("宋体");
text2.Draw("楷体_GB2312");
glFlush();
类的声明和实现如下:
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#include <string>
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#include <GL/glut.h>
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using namespace std;
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class COpenGLText
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![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
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public:
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//构造文字
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COpenGLText();
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virtual ~COpenGLText();
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//绘制制定字体的文字,字体只在第一次绘制时进行设置,之后可以传入空值
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void Draw(char *strFontName);
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//释放文字所占空间
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void Free();
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//文字字符串
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string m_str;
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//字符串高度
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double m_dHeight;
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//字符串位置
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double m_dX;
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double m_dY;
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protected:
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BOOL GenList();
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BOOL GenCharsLists(char *strFontName);
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int m_iDisplayList;
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};
32![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
33![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**/////////////////////////////////////////////////////////////////////// 34![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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// COpenGLText Class
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/**///////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////// 40![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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// Construction/Destruction
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43![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
/**/////////////////////////////////////////////////////////////////////// 44![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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COpenGLText::COpenGLText()
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![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
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m_dX=0;
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m_dY=0;
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m_str="abc中国";
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m_dHeight=100;
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m_iDisplayList=0;
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}
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COpenGLText::~COpenGLText()
55![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
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Free();
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}
58![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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BOOL COpenGLText::GenCharsLists(char *strFontName)
60![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
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HDC hdc;
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const char *str=m_str.c_str()
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hdc=CreateDC( "DISPLAY", "", "", NULL );
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int iNum=_mbslen((const unsigned char *)str);
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m_iDisplayList=glGenLists(iNum+1);
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HFONT hNewCFont;
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LOGFONT CLogFont; //存储当前字体参数
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//初始化字体参数
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memset( &CLogFont, 0, sizeof(LOGFONT) );
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CLogFont.lfEscapement = CLogFont.lfOrientation = 0;
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CLogFont.lfWeight = FW_NORMAL;
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CLogFont.lfCharSet = GB2312_CHARSET;
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CLogFont.lfOutPrecision = OUT_DEFAULT_PRECIS;
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CLogFont.lfQuality=DEFAULT_QUALITY;
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CLogFont.lfPitchAndFamily = DEFAULT_PITCH | FF_SWISS;
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strcpy( CLogFont.lfFaceName, LPCTSTR(strFontName) );
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CLogFont.lfHeight=-10;
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CLogFont.lfWidth=0;
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hNewCFont=CreateFontIndirect(&CLogFont);
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HFONT hOldFont=(HFONT)SelectObject(hdc,hNewCFont);
85![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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int i=0,j=0,iTotal=strlen(str);;
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UINT nChar=0;
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while(i<iTotal)
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{
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j++;
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if(IsDBCSLeadByte(str[i]))
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{
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nChar=((unsigned char)str[i])*0x100+(unsigned char)str[i+1];
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i+=2;
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}
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else
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{
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nChar=str[i];
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i++;
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}
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GLYPHMETRICSFLOAT agmf[1];
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BOOL bOK=wglUseFontOutlines(hdc,nChar,1,m_iDisplayList+j,0.002f,0,WGL_FONT_POLYGONS,agmf);
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}
108![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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SelectObject(hdc,hOldFont);
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DeleteObject(hNewCFont);
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DeleteDC(hdc);
112![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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return TRUE;
114![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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}
116![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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BOOL COpenGLText::GenList()
118![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
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int iNum=_mbslen((const unsigned char *)m_str.c_str());
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glNewList( m_iDisplayList, GL_COMPILE);
121![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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for(int i=1;i<=iNum;i++)
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{
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glPushMatrix();
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//此处修改文字间距
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glTranslated(m_dX+m_dHeight*(i-1),m_dY,0);
130![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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glScaled(m_dHeight,m_dHeight,1);
132![](http://www.cppblog.com/Images/OutliningIndicators/InBlock.gif)
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glCallList(m_iDisplayList+i);
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glPopMatrix();
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}
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glEndList();
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return TRUE;
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}
142![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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void COpenGLText::Free()
144![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
145
if(glIsList(m_iDisplayList))
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glDeleteLists(m_iDisplayList,_mbslen((const unsigned char *)m_str.c_str())+1);
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m_iDisplayList=0;
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}
149![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
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void COpenGLText::Draw(char *strFontName)
151![](http://www.cppblog.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cppblog.com/Images/OutliningIndicators/ContractedBlock.gif)
{
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if(!glIsList(m_iDisplayList))
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{
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GenCharsLists(strFontName);
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GenList();
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}
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glCallList(m_iDisplayList);
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}
159![](http://www.cppblog.com/Images/OutliningIndicators/None.gif)
posted on 2007-04-12 15:26
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