iphone 如何实现全屏截图

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3. 本文摘自：http://www.devdiv.com/forum.php?mod=viewthread&tid=58560&highlight=%BD%D8%CD%BC
4. 本文参考：http://www.devdiv.com/forum.php?mod=viewthread&tid=31687&highlight=%BD%D8%CD%BC
5. UIGraphicsBeginImageContext(pictureView.bounds.size); 
                
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7. [pictureView.layer renderInContext:UIGraphicsGetCurrentContext()]; 
   
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9. UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
   
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11. UIGraphicsEndImageContext();
    
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13. UIImageWriteToSavedPhotosAlbum(viewImage, nil, nil, nil);