ios 屏幕截图切圆角切不掉怎么解决？白线也去不掉怎么办？

屏幕截图，图片的底部为啥有白线？并且自己的屏幕图片明明切图了，但是为啥截的图还是有会没有切圆角的那部分？what？why？
demo在这里

问题一：为啥屏幕截图底部会有白线？

1.可能会出现白线的代码如下：

//对某个view进行截图
-(UIImage *)screenshotsImageFromView:(UIView *)view {
    
    JCShowView *showView  = (JCShowView *)view;
    CGRect screenRect = [showView bounds];
    NSInteger scale = 1;
    if ([[UIScreen mainScreen]respondsToSelector:@selector(scale)]) {
        CGFloat tmp = [[UIScreen mainScreen]scale];
        if (tmp > 1.5) {
            scale = 2.0;
        }
        if (tmp > 2.5) {
            scale=3.0;
        }
    }
    if (scale > 1.5) {
        UIGraphicsBeginImageContextWithOptions(screenRect.size, NO, scale);
    } else {
        UIGraphicsBeginImageContext(screenRect.size);
    }
    
    CGContextRef ctx = UIGraphicsGetCurrentContext();
    [showView.layer renderInContext:ctx];
    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return image;
}

2.常规测试了也没发现啥问题，最后查阅资料问题出在这行代码了UIGraphicsBeginImageContextWithOptions(screenRect.size, NO, scale);

原因是因为当屏幕的高度是CGFloat类型的时候会出现白线，所以把高度通过NSNumber转成 NSInteger好了、优化后代码如下：

        NSInteger screenH = [[NSNumber numberWithDouble:screenRect.size.height] integerValue];
        UIGraphicsBeginImageContextWithOptions(CGSizeMake(screenRect.size.width, screenH), NO, scale)

问题一：为啥屏幕截图上的图片圆角已经切了，为啥最后相册查看的时候还是显示没切掉的圆角呢？

有问题的图如下：

Snip20200224_2.png

分析：圆角应该在图片上切，而图片的父视图的背景应该在截屏的一瞬间做下处理。优化后在截图正常了。如下图：

  CGContextRef ctx = UIGraphicsGetCurrentContext();
  #截取的时候先修改成黑色背景
    showView.backgroundColor = [UIColor blackColor];
    [showView.layer renderInContext:ctx];
    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
#完毕之后在修改成白色背景
    showView.backgroundColor = [UIColor whiteColor];  

WechatIMG214.jpeg

最终代码如下：

-(UIImage *)screenshotsImageFromView:(UIView *)view {
   
   JCShowView *showView  = (JCShowView *)view;
   CGRect screenRect = [showView bounds];
   NSInteger scale = 1;
   if ([[UIScreen mainScreen]respondsToSelector:@selector(scale)]) {
       CGFloat tmp = [[UIScreen mainScreen]scale];
       if (tmp > 1.5) {
           scale = 2.0;
       }
       if (tmp > 2.5) {
           scale=3.0;
       }
   }
   if (scale > 1.5) {
       //        UIGraphicsBeginImageContextWithOptions(screenRect.size, NO, scale);
       //这里的屏幕高度需要设置成NSInteger类型的否则截图底部会有白线
       NSInteger screenH = [[NSNumber numberWithDouble:screenRect.size.height] integerValue];
       UIGraphicsBeginImageContextWithOptions(CGSizeMake(screenRect.size.width, screenH), NO, scale);
   } else {
       UIGraphicsBeginImageContext(screenRect.size);
   }
   
   CGContextRef ctx = UIGraphicsGetCurrentContext();
   showView.backgroundColor = [UIColor blackColor];
   [showView.layer renderInContext:ctx];
   UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
   UIGraphicsEndImageContext();
   showView.backgroundColor = [UIColor whiteColor];
   return image;
}