How to fix glGrab.c for Intel machines? (Was: Re: Fast screen shots for VNC like functionality...)

• Subject: How to fix glGrab.c for Intel machines? (Was: Re: Fast screen shots for VNC like functionality...)
• From: David Niemeijer <email@hidden>
• Date: Thu, 25 May 2006 16:37:37 +0200
• Delivered-to: email@hidden
• Delivered-to: email@hidden

Hi Mike,

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:

Thanks,

david.
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