Printing an OpenGL Image

You can print OpenGL images rendered in enhanced metafiles. When you render to a printer device (HDC) it must be backed by a metafile spooler. OpenGL uses memory for depth, color, and other buffers to store graphics output to a printer. Because typical printer resolution requires a significant amount of memory to store the graphics output, printing an OpenGL image might require more memory than is available in the system. To overcome this limitation, the current implementation of OpenGL prints OpenGL graphics in bands. However, this increases the time it takes to print OpenGL images.

Before you print an OpenGL image, you must call the StartDoc function to complete the initialization of a printer device context (DC). After calling StartDoc, you can create rendering contexts (HGLRC) to render to the printer device. If you create rendering contexts before calling StartDoc, there is no way to determine whether a metafile is spooled.

The following code sample shows how to print an OpenGL image:

HDC            hDC;
DOCINFO        di;
HGLRC          hglrc;

// Call StartDoc to start the document
StartDoc( hDC, &di );

// Prepare the printer driver to accept data
StartPage(hDC);

// Create a rendering context using the metafile DC
hglrc = wglCreateContext ( hDCmetafile );

// Do OpenGL rendering operations here
    . . .
wglMakeCurrent(NULL, NULL); // Get rid of rendering context
    . . .
EndPage(hDC); // Finish writing to the page
EndDoc(hDC); // End the print job
 

For more information on using metafiles, see Enhanced Metafile Operations.