把当前页面绘制为图片

 法1：

  UIGraphicsBeginImageContextWithOptions((view.bounds.size), NO , 0);//绘制出来的不模糊

 //   UIGraphicsBeginImageContext()//这种的绘制会模糊

    CGContextRef ctx = UIGraphicsGetCurrentContext();

    [view.layer renderInContext:ctx];

    UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

    UIGraphicsEndImageContext();

法2：

 UIGraphicsBeginImageContextWithOptions((view.bounds.size), NO , 0);

 [view drawRect:CGRectMake(0, 0, view.frameWidth, view.frameHeight)];

 UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();

 UIGraphicsEndImageContext();