iOS 屏幕快照（view 截图/快照）

1. layer 快照

- (UIImage *)convertViewToImage:(UIView *)view
{
    // 第二个参数表示是否非透明。如果需要显示半透明效果，需传NO，否则YES。第三个参数就是屏幕密度了
    UIGraphicsBeginImageContextWithOptions(view.bounds.size,YES,[UIScreen mainScreen].scale);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

2. view 快照

- (UIImage *)snapsHotView:(UIView *)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size,YES,[UIScreen mainScreen].scale);
    [view drawViewHierarchyInRect:view.bounds afterScreenUpdates:NO];
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}