MFC+OpenGL 怎么计算投影区域在窗口中的大小

[Ilson_]

我用的是正交投影gluOrtho2D以纹理贴图的方式显示一张BMP位图，当我滚动鼠标滚轮时位图会缩小放大；我要求的是纹理贴图在窗口中的大小，如红色框大小：




这是我显示图片的代码:

//贴图的矩形大小与图片比例一致  
#define MAPWIDTH    20.0  
#define MAPHIGHT    GLfloat(20.0 / (1920.0 / 1080.0)) 

//背景图  
void CDrawView::DrawImage()  
{  
    glPushMatrix();  
    glLoadIdentity();  
  
    glScalef(mScale_, mScale_, 1);    //横纵坐标缩放量  
    glTranslatef(mTranslateX_ * mVcWidthRatio_, mTranslateY_ * mVcHightRatio_, 0);    //横纵坐标平移量  
  
  
    //纹理图像的坐标范围是从（0,0）到（1,1），左下角为（0,0），右上角为（1,1）  
    glEnable(GL_TEXTURE_2D);  
    glBegin(GL_QUADS);  
    glTexCoord2d(0.0, 0.0);  
    glVertex2d(-MAPWIDTH, -MAPHIGHT);  
  
    glTexCoord2d(1.0, 0.0);  
    glVertex2d(MAPWIDTH,  -MAPHIGHT);  
  
    glTexCoord2d(1.0, 1.0);  
    glVertex2d(MAPWIDTH,   MAPHIGHT);  
  
    glTexCoord2d(0.0, 1.0);  
    glVertex2d(-MAPWIDTH,  MAPHIGHT);  
    glEnd();  
    glDisable(GL_TEXTURE_2D);  
  
    glPopMatrix();  
}  
 

这是OnSize()函数代码:

mViewHalfWidth_ = 12;  
mViewHalfHight_ = 12; 

void CDrawView::OnSize(UINT nType, int cx, int cy)  
{  
    CScrollView::OnSize(nType, cx, cy);  
      
    // TODO: Add your message handler code here  
    //以下两行保证窗口大小变化后图像中心点不发生变化  
    mTranslateX_ *= (GLfloat)(cx * 1.0 / mClientWidth_);  
    mTranslateY_ *= (GLfloat)(cy * 1.0 / mClientHight_);  
  
    mClientWidth_ = cx;  
    mClientHight_ = cy;  
    if (mClientHight_==0)       // Prevent A Divide By Zero By 防止除以0  
    {  
        mClientHight_=1;        // Making Height Equal One  
    }  
    if (mClientWidth_==0)       // Prevent A Divide By Zero By  
    {  
        mClientWidth_=1;        // Making Height Equal One  
    }  
  
    mVcWidthRatio_ = (GLfloat)(mViewHalfWidth_ * 2 / mClientWidth_);//视窗比(视景体/窗口)  
    mVcHightRatio_ = (GLfloat)(mViewHalfHight_ * 2 / mClientHight_);  
  
    wglMakeCurrent(mhDC_, mhGLContext_);  
    glViewport(0, 0, cx, cy);               // Reset The Current Viewport  
    glMatrixMode(GL_PROJECTION);            // Select The Projection Matrix 选择投影矩阵  
    glLoadIdentity();                       // Reset The Projection Matrix  
  
    //改变窗口大小时，使视图等比缩放    
    //正交投影  
    GLdouble glScale = (GLdouble)cx / cy;  
    if (cx <= cy)  
        gluOrtho2D(-mViewHalfWidth_, mViewHalfWidth_, -mViewHalfHight_ / glScale, mViewHalfHight_ / glScale);  
    else  
        gluOrtho2D(-mViewHalfWidth_ * glScale, mViewHalfWidth_ * glScale, -mViewHalfHight_, mViewHalfHight_);  
  
    glMatrixMode(GL_MODELVIEW);                            // Select The Modelview Matrix  
    glLoadIdentity();                                      // Reset The Modelview Matrix  
  
    CurrentGLpoint(CPoint(), TRUE);  
}  

请问我该怎么求在窗口中投影的大小(图片的大小、红框大小)，随着缩放量改变而改变

[Ilson_]

//计算这个视图的总大小
//这里做判断是因为要根据OnSize函数里面设置gluOrtho2D()平行投影的大小计算
	GLdouble fScale = (GLdouble)mClientWidth_ / mClientHight_;
	if (mClientWidth_ <= mClientHight_)
	{
                //mViewHalfWidth_ * 2实景体宽度  mViewHalfHight_ * 2 / fScale实景体高度
                //(mViewHalfWidth_ * 2 / mClientWidth_ 求出实景体与窗口宽的比
                //MAPWIDTH * 2纹理贴图时给定的矩形框的宽 MAPHIGHT * 2纹理贴图时给定的矩形框的高 然后各乘于缩放量mScale_ 得到缩放后的纹理矩形框大小
                //然后用    缩放后的纹理矩形宽/实景体与窗口宽的比   得到窗口的投影大小
                //else分支也是一样
		int w = (MAPWIDTH * 2 * mScale_) / (mViewHalfWidth_ * 2 / mClientWidth_);
		int  h = (MAPHIGHT * 2 * mScale_) / (mViewHalfHight_ * 2 / fScale / mClientHight_);
	}
	else
	{
		int w = (MAPWIDTH * 2 * mScale_) / (mViewHalfWidth_ * 2 * fScale / mClientWidth_);
		int h = (MAPHIGHT * 2 * mScale_) / (mViewHalfHight_ * 2 / mClientHight_);
	}