Re: CGWindowListCreateImage fails on Snow Leopard with kCGNullWindowID
On Sep 10, 2009, at 7:32 AM, Jason Foreman wrote: I am attempting to use the CGWindowListCreateImage function to capture a desktop screenshot. The following code (taken straight from the SonOfGrab sample) works on Leopard, but is failing on Snow Leopard: CGImageRef screenShot = CGWindowListCreateImage(CGRectInfinite, kCGWindowListOptionOnScreenOnly, kCGNullWindowID, kCGWindowImageDefault); On Leopard, the returned CGImageRef is what I expect: an image of the desktop and all on-screen windows. On Snow Leopard, the CGImageRef is NULL and the following message is printed to the console: Error: CGImageCreate: invalid image bits/pixel or bytes/row. I have filed a bug (7212104), but wonder if there is a workaround that I can use in the meantime, or if I should just use another method of capturing the desktop. Has anyone else encountered this issue? Your bug will end up dup'd to rdar://problem/7022171. The basic problem is using CGRectInfinite from a 32-bit process when the Window Server is running as a 64-bit process – when the rect comes out at the other end it is no longer interpreted as infinite but rather as very very large. Since you can't create an image that large, the creation code fails and you get back a NULL CGImageRef instead. The current best work around is to determine a proper bounding box for the desktop and pass it for the given rect. -- David Duncan Apple DTS Animation and Printing ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to arch...@mail-archive.com
Re: CGWindowListCreateImage fails on Snow Leopard with kCGNullWindowID
On Sep 10, 2009, at 12:34 PM, David Duncan wrote:
On Sep 10, 2009, at 7:32 AM, Jason Foreman wrote:
CGImageRef screenShot = CGWindowListCreateImage(CGRectInfinite,
kCGWindowListOptionOnScreenOnly, kCGNullWindowID,
kCGWindowImageDefault);
On Snow Leopard, the CGImageRef is NULL and the following message
is printed to the console:
Error: CGImageCreate: invalid image bits/pixel or bytes/row.
Your bug will end up dup'd to rdar://problem/7022171. The basic
problem is using CGRectInfinite from a 32-bit process when the
Window Server is running as a 64-bit process – when the rect comes
out at the other end it is no longer interpreted as infinite but
rather as very very large. Since you can't create an image that
large, the creation code fails and you get back a NULL CGImageRef
instead.
The current best work around is to determine a proper bounding box
for the desktop and pass it for the given rect.
Thanks David, your suggestion works great. I appreciate the quick
response.
For the benefit of the archives and anyone else having a similar
issue, here is how I calculate the bounding box:
NSRect desktopRect = NSZeroRect;
for (NSScreen *screen in [NSScreen screens])
{
desktopRect = NSUnionRect(desktopRect, [screen frame]);
}
This seems to give me exactly what I want when passed to
CGWindowListCreateImage.
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