我正在制作具有一堆小窗口和控件的应用程序(所以它是2D渲染),我想将每个窗口和控件渲染到它自己的位图(没有那么多).这有：
@H_404_1@uses dglOpenGL;
...
var BMP: TBitmap;
DC,RC: HDC;
...
function TMainForm.Init: Boolean;
begin
Result := InitOpenGL;
if Result = True then
begin
BMP := TBitmap.Create;
BMP.PixelFormat := pf24bit;
BMP.Width := 1280;
BMP.Height := 1024;
DC := (BMP.Canvas.Handle);
RC := CreateRenderingContext(DC,[opGDI,opDoubleBuffered],//tried changing,didn't help
24,24,0);
ActivateRenderingContext(DC,RC);
glClearColor(0.27,0.4,0.7,0.0);//Light blue
glViewport(0,1280,1024);
glMatrixMode(GL_PROJECTION);
glLoadIdentity;
glOrtho(0,1024,-1,10);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity;
end;
end;
渲染程序：
@H_404_1@glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT); //Red quad glColor3f(1,0); glBegin(GL_QUADS); glVertex2f(100,100); glVertex2f(1280-100,1024-100); glVertex2f(100,1024-100); glend; //Output SwapBuffers(DC);但是没有输出.
如果我使用MainForm.Canvas.Draw(0,BMP);然后会出现白色矩形.
我想在位图上渲染东西,因为我可以使用位图做很多事情(在它上面绘制图形,绘制文本,模糊),但如果有其他方法可以在屏幕外渲染,那么它没关系……
那么如何设置我的应用程序进行屏幕外渲染？
必须创建与目标设备上下文匹配的OpenGL上下文.对于Windows,它们的创建方式与位图不同.看到
http://msdn.microsoft.com/en-us/library/windows/desktop/dd368826(v=vs.85).aspx尤其是dwFlags,其中包括其他
http://msdn.microsoft.com/en-us/library/windows/desktop/dd368826(v=vs.85).aspx尤其是dwFlags,其中包括其他
PFD_DRAW_TO_WINDOW The buffer can draw to a window or device surface.
PFD_DRAW_TO_BITMAP The buffer can draw to a memory bitmap.
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)
@H_404_1@// flushes the OpenGL error queue and // counts the total 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; }