windows – OpenGL – 直接渲染到位图

但是,您不应该抢先为DIB DC创建渲染上下文.为什么？因为它会很慢,因为在DIB部分上的OpenGL渲染上下文将使用仅支持在cpu上运行的OpenGL-1.1的软件光栅化器.

相反,您应该创建一个Framebuffer对象,附加一个颜色渲染缓冲附件,并在完成glReadPixels时进入您的DIBSection.更容易,更快.

由于评论请求而更新

(我不知道为什么StackOverflow没有正确的语法着色,即找出评论的位置和不在哪里)

// flushes the OpenGL error queue and
// counts the @R_334_10586@l number of errors
int flushGLErrors(void)
{
    int i = 0;
    while( glGetError() != GL_NO_ERROR ) {
        i++;
    }

    return i;
}

// returns a HBITMAP or NULl.
// The HBITMAP must be freed using deleteObject 
HBITMAP ReadPixelsToHBITMAP(
    int x,int y,int width,int height )
{
    void *PDAta = NULL;

    /* Note that this values only makes sense if we kNow a target
     * output size like if we put the image to paper. */ 
    const int physical_resolution = 2835; /* 72 DPI */

    BITMAPINFOHEADER bmih = {
        /* .biSize          = */ sizeof(bmih),/* .biWidth         = */ width,/* .bi.Height       = */ height,/* .biPlanes        = */ 1,/* mandatory */
        /* .biBitCount      = */ 24,/* 8 bits per pixel */
        /* .biCompression   = */ BI_RGB,/* uncompressed */
        /* .biSizeImage     = */ 0,/* implicit */
        /* .biXPelsPerMeter = */ physical_resolution,/* ignored */
        /* .biYPelsPerMeter = */ physical_resolution,/* ignored */
        /* .biClrUsed       = */ 0,/* no palette */
        /* .biClrImportant  = */ 0
    };

    HBITMAP hbm = CreateDIBSection(
        hdc,/* may be different than the DC used for OpenGL */
        (PBITMAPINFO)&bmih,/* can do this cast,because no palette is used */
        DIB_RGB_COLORS,&PDAta,NULL,0
    );

    if( !hbm ) {
        return NULL;
    }

    flushGLErrors();

    glPixelStorei(GL_PACK_SWAP_BYTES,GL_falSE);
    glPixelStorei(GL_PACK_LSB_FIRST,GL_TRUE);
    glPixelStorei(GL_PACK_ROW_LENGTH,0);
    glPixelStorei(GL_PACK_IMAGE_HEIGHT,0);
    glPixelStorei(GL_PACK_SKIP_PIXELS,0);
    glPixelStorei(GL_PACK_SKIP_ROWS,0);
    glPixelStorei(GL_PACK_ALIGNMENT,1);

    if( glGetError() != GL_NO_ERROR ) {
        deleteObject(hbm);
        return NULL;
    }

    glReadPixels(x,y,width,height,GL_BGR,GL_UNSIGNED_BYTE,PDAta);

    if( glGetError() != GL_NO_ERROR ) {
        deleteObject(hbm);
        return NULL;
    }

    return hbm;
}