-- originally posted a few days ago, but now changed the title to
better match the question
Hi Mike,
At 9:26 -0700 26/4/06, Mike Paquette wrote:
OpenGL can help here, as it includes the ability to convert pixel
formats, and can even deal with hardware-specific pixel reading
problems such as microtiling, or getting the correct framebuffer
when full screen buffer swapping (the GL version of page flipping)
is in effect. OpenGL will also use a DMA transfer for reading the
framebuffer content, where available.
OpenGL provides both a synchronous read path suitable for simple
screen captures using glReadPixels, and a fast asynchronous path
using the texture read mechanism, which is a bit more complex, but
works well for repeated capture operations, such as screencasting or
recording a movie from the screen.
Here's a simple mechanism that can be used to read a rectangle from
a display to a CGImageRef, as an example to help you get started.
It's more comment than code:
Your code sample works pretty well, except for one thing. On Intel
machines the colors look pretty awkward. I am sure some swapping
needs to take place, but not being a quartz/opengl specialist, I am
not sure what the best approach would be. Would you mind indicating
what would need to be done to make the sample code work correctly on
both Intel and PowerPC?
Thanks,
david.
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