将view的layer层渲染成一张图片

//打开图片上下文
UIGraphicsBeginImageContextWithOptions(self.view.bounds.size, NO, 1);

//将本App的一个view的layer层渲染成一张图片
CGContextRef context = UIGraphicsGetCurrentContext();
[self.view.layer renderInContext:context];

//导出图片
UIImage * newImage = UIGraphicsGetImageFromCurrentImageContext();

//将图片写出到桌面
[UIImagePNGRepresentation(newImage) writeToFile:@"/Users/mengmei/Desktop/截屏.png" atomically:YES];

//关闭图片上下文
UIGraphicsEndImageContext();