Q: Any faster image copying than with "XPutImage" ? - comp.windows.x

Message from discussion Q: Any faster image copying than with "XPutImage" ?

Peter Mattis

More options Oct 7 1995, 3:00 am

Newsgroups: comp.windows.x

From: p...@soda.CSUA.Berkeley.EDU (Peter Mattis)

Date: 1995/10/07

Subject: Re: Q: Any faster image copying than with "XPutImage" ?

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>I am using XFree3.1.2 on a Pentium PC with an accelerated Diamond Stealth V64
>video card (PCI); mainly in 16bpp TrueColor mode.

>My problem is that the "XPutImage" function is rather slow, even if the
>GC is set to "GXcopy" which means that the image could be written directly
>into the video ram. I use the same format as the server does,
>ie 16bpp ZImage, so no transformation has to take place.

The reason it is so slow is that every time an XPutImage takes place
Xlib as to copy the image data over its connection to the X-server.
The solution is easy: use XShmPutImage, XShmCreateImage and XShmAttach
to use shared memory images.

Hint: I know this is possible using XFree86. I've done it. As an example
of the speed you can get: I can get 45 fps at 640x480 at 16bpp on my
p5-133 w/ Matrox Millenium under Accelerated-X. That includes "erasing"
the image each frame. Doing straight blits that goes up to about 60fps.

Peter Mattis

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