如何获取不带图标和多个屏幕窗口的桌面墙纸屏幕？

Question

在我的可可应用程序中，我想为多屏幕拍摄桌面墙纸的屏幕快照，我发现此link是我为单屏幕制作的，但是，我发现很难在多屏幕上使用。那么我将如何在多个屏幕上做到这一点？

这是我的代码

- (NSImage*) desktopAsImageWithScreen:(NSScreen *)screen {

NSDictionary *deviceDescription = [screen deviceDescription];

CFMutableArrayRef windowIDs = CFArrayCreateMutable(NULL, 0, NULL);
CFArrayRef allWindowIDs = CGWindowListCreate(kCGWindowListOptionOnScreenBelowWindow, kCGDesktopIconWindowLevel);

NSLog(@"min window level: %d", kCGMinimumWindowLevel);
NSLog( @"looking for windows on level: %d", kCGDesktopWindowLevel );
NSLog( @"NOt actually looking for windows on level: %d", kCGMinimumWindowLevel );
NSLog( @"NOt actually looking for windows on the dock level: %d", kCGDockWindowLevel );
if (allWindowIDs)
{

    CFArrayRef windowDescs = CGWindowListCreateDescriptionFromArray(allWindowIDs);
    for (CFIndex idx=0; idx<CFArrayGetCount(windowDescs); idx++)
    {
        CFDictionaryRef dict = CFArrayGetValueAtIndex(windowDescs, idx);
        CFStringRef ownerName = CFDictionaryGetValue(dict, kCGWindowOwnerName);
        NSLog(@"owner name = %@", ownerName);
        if (CFStringCompare(ownerName, CFSTR("Dock"), 0) == kCFCompareEqualTo )
        {
            // the Dock level has the dock and the desktop picture
            CGRect windowBounds;
            BOOL success = CGRectMakeWithDictionaryRepresentation(
                                                                  (CFDictionaryRef)(CFDictionaryGetValue(dict, kCGWindowBounds)),
                                                                  &windowBounds);

            NSRect screenBounds = screen.frame;
            CFNumberRef windowLayer = CFDictionaryGetValue(dict, kCGWindowLayer);

            //CFDictionaryGetValue(dict, kCGWindowBounds)
            NSLog(@"window bounds %f, %f, matches screen bounds? %d, on level %@",
                  windowBounds.size.width,
                  windowBounds.size.height,
                  CGRectEqualToRect(windowBounds, screenBounds),
                  windowLayer
                  );

            NSNumber* ourDesiredLevelNumber = [NSNumber numberWithInt: kCGDesktopWindowLevel - 1];
            if ( CGRectEqualToRect(windowBounds, screenBounds) && [ourDesiredLevelNumber isEqualToNumber: (__bridge NSNumber * _Nonnull)(windowLayer)] )
                CFArrayAppendValue(windowIDs, CFArrayGetValueAtIndex(allWindowIDs, idx));
        }

    }
    CFRelease(windowDescs);
    CFRelease(allWindowIDs);
}

CGImageRef cgImage = CGWindowListCreateImageFromArray( screen.frame, windowIDs, kCGWindowImageDefault);

// Create a bitmap rep from the image...
NSBitmapImageRep *bitmapRep = [[NSBitmapImageRep alloc] initWithCGImage:cgImage];
// Create an NSImage and add the bitmap rep to it...
NSImage *image = [[NSImage alloc] init];
[image addRepresentation:bitmapRep];
//[bitmapRep release];

return image;

}

有什么建议吗？

预先感谢！