在窗口调整大小时保留2D对象的长宽比 [英] Preserve aspect ratio of 2D object on window resize

问题描述

我有一个Windows(XP)应用程序，该应用程序需要在窗口中显示一个二维矩形.不得剪切矩形(即必须始终完全位于视口内)，并且必须在调整大小时保留其长宽比.当前，处理布局的方法使矩形的纵横比失真以匹配窗口.我希望矩形缩放到窗口并在窗口中居中(再次，不进行裁剪).目前的方法如下. lWinDist和lMaxDepth是要显示的矩形的宽度和高度(如果重要，以48英寸为单位):

I have a Windows (XP) application which needs to display a two-dimensional rectangle within a window. The rectangle must not be clipped (i.e. must always lie completely within the viewport), and must preserve its aspect ratio on resize. Currently, the method which handles layout distorts the aspect ratio of the rectangle to match the window. I want the rectangle to scale to the window and be centered in the window (again, without clipping). The method as it stands is below. lWinDist and lMaxDepth are the width and height of the rectangle to be displayed (in 48ths of an inch, if it matters):

void CRoRRecView::RedoLayout( long lWinDist, long lMaxDepth )
{
    CDC* pDC = GetDC() ;

    if ( pDC != NULL )
    {
        m_lWinDist = lWinDist;
        GetClientRect( m_rectClient ) ;
        int nClientWidth = m_rectClient.Width();
        int nClientHeight = m_rectClient.Height();
        glViewport( 0, 0, nClientWidth, nClientHeight );

        glMatrixMode( GL_PROJECTION);
        glLoadIdentity();

        m_fWinXDist = (float) lWinDist ;
        m_fWinYDist = lMaxDepth ;
        m_fAspectRatio = m_fWinXDist / m_fWinYDist;

        glOrtho(0.0, m_fWinXDist, 0.0, m_fWinYDist, -1, 1 ) ;

        glRotatef(180.0, 0,1,0); 
        glTranslatef( (float)(-1 * lWinDist),0,0 ); // Translate across the x axis

        glMatrixMode( GL_MODELVIEW );
        glLoadIdentity();

        ReleaseDC( pDC ) ;
    }
}

推荐答案

此方案应按预期缩放:

// g++ main.cpp -lglut -lGL
#include <GL/glut.h>

void display()
{
    glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    double w = glutGet( GLUT_WINDOW_WIDTH );
    double h = glutGet( GLUT_WINDOW_HEIGHT );
    double ar = w / h;
    glOrtho( -2 * ar, 2 * ar, -2, 2, -1, 1);

    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    glColor3ub( 255, 0, 0 );
    glBegin( GL_QUADS );
    glVertex2i( -1, -1 );
    glVertex2i(  1, -1 );
    glVertex2i(  1,  1 );
    glVertex2i( -1,  1 );
    glEnd();

    glutSwapBuffers();
}

int main( int argc, char **argv )
{
    glutInit( &argc, argv );
    glutInitDisplayMode( GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE );
    glutInitWindowSize( 640, 480 );
    glutCreateWindow( "Aspect Ratio" );
    glutDisplayFunc( display );
    glutMainLoop();
    return 0;
}

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