截取当前屏幕图像，并将图片存入沙盒中。

    CGRect rect = [self.viewbounds];    UIGraphicsBeginImageContext(rect.size);    CGContextRef context =UIGraphicsGetCurrentContext();    [self.view.layerrenderInContext:context];        UIImage *image =UIGraphicsGetImageFromCurrentImageContext();    UIGraphicsEndImageContext();       NSData *data = UIImagePNGRepresentation(image);//转换成二进制文件   NSString *path = NSHomeDirectory();   NSLog(@"%@",path);    [data writeToFile:[NSStringstringWithFormat:@"%@/Documents/ss.png",path]atomically:YES];