ios：app切换后台时添加模糊处理，截屏数据安全

背景：安全扫描过程中发现我们的App切后台的时候，截屏页面没有模糊处理，客户认为不安全，需要我们类似于银行App那种模糊处理，就有了以下解决方案。

实现思路：

1、当我们的app应用进入后台前截屏图片高斯模糊处理，
2、当我们的app进入后台后把处理了的模糊图片添加到window上
3、当我们的app进入前台后remove模糊图片

具体实现代码： 创建一个单例类来实现上述步骤:

WSScreenShotManager.h类

@interface WSScreenShotManager : NSObject

/**
 单例创建对象

 @return self
 */
+ (instancetype)shared;

/**
 截屏处理
 */
- (void)screenShot;

- (void)showMask;

- (void)hiddenMask;

WSScreenShotManager.m类

static WSScreenShotManager * manager = nil;


@interface WSScreenShotManager ()

@property (nonatomic, strong) UIImageView *screenShotImageV;


@end

@implementation WSScreenShotManager

+ (instancetype)shared {
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        manager = [[self alloc] init];
    });
    return manager;
}

- (void)screenShot {
    CGSize imageSize = CGSizeZero;
    //屏幕朝向
    UIInterfaceOrientation orientation = [UIApplication sharedApplication].statusBarOrientation;
    if (UIInterfaceOrientationIsPortrait(orientation))
        imageSize = [UIScreen mainScreen].bounds.size;
    else
        imageSize = CGSizeMake([UIScreen mainScreen].bounds.size.height, [UIScreen mainScreen].bounds.size.width);
    
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    //按理应取用户看见的那个window
    
    for (UIWindow *window in [[UIApplication sharedApplication] windows])
    {
        CGContextSaveGState(context);
        CGContextTranslateCTM(context, window.center.x, window.center.y);
        CGContextConcatCTM(context, window.transform);
        CGContextTranslateCTM(context, -window.bounds.size.width * window.layer.anchorPoint.x, -window.bounds.size.height * window.layer.anchorPoint.y);
        if (orientation == UIInterfaceOrientationLandscapeLeft)
        {
            CGContextRotateCTM(context, M_PI_2);
            CGContextTranslateCTM(context, 0, -imageSize.width);
        }
        else if (orientation == UIInterfaceOrientationLandscapeRight)
        {
            CGContextRotateCTM(context, -M_PI_2);
            CGContextTranslateCTM(context, -imageSize.height, 0);
        } else if (orientation == UIInterfaceOrientationPortraitUpsideDown) {
            CGContextRotateCTM(context, M_PI);
            CGContextTranslateCTM(context, -imageSize.width, -imageSize.height);
        }
        
        if ([window respondsToSelector:@selector(drawViewHierarchyInRect:afterScreenUpdates:)])
        {
            [window drawViewHierarchyInRect:window.bounds afterScreenUpdates:YES];
        }
        else
        {
            [window.layer renderInContext:context];
        }
        CGContextRestoreGState(context);
    }
    //截取屏幕图片
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    //截屏图片高斯模糊处理后
    UIImage *gaussianImage = [self coreGaussianBlurImage:image blurNumber:8];
    //生成控件
    UIImageView *bgImgv = [[UIImageView alloc] initWithImage:gaussianImage];
    bgImgv.frame = CGRectMake(0, 0, imageSize.width, imageSize.height);
    self.screenShotImageV = bgImgv;
}

/**
 模糊 处理
 @param image 要处理的image
 @param blur 模糊度
 @return 处理后的image
 */
- (UIImage *)coreGaussianBlurImage:(UIImage * _Nonnull)image  blurNumber:(CGFloat)blur{
    
    if (!image) {
        return nil;
    }
    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *inputImage = [CIImage imageWithCGImage:image.CGImage];
    
    CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
    [filter setValue:inputImage forKey:kCIInputImageKey];
    [filter setValue:[NSNumber numberWithFloat:blur] forKey:@"inputRadius"];
    CIImage *result = [filter valueForKey:kCIOutputImageKey];
    CGImageRef cgImage = [context createCGImage:result fromRect:[inputImage extent]];
    
    UIImage *blurImage = [UIImage imageWithCGImage:cgImage];
    
    CGImageRelease(cgImage);
    
    return blurImage;
    
}
//显示window
- (void)showMask {
    
    [[UIApplication sharedApplication].delegate.window addSubview:self.screenShotImageV];
}
//隐藏window
- (void)hiddenMask {
    
    [self.screenShotImageV removeFromSuperview];
}

使用方法：

1. app将要切换后台时截屏保存 并处理高斯模糊图片
2. app进入后台后image以window控件添加到app当前window上面
3. app重新切换到前台时移除image window

- (void)applicationWillResignActive:(UIApplication *)application
{
    //将要注销响应回到后台的时候截取当前屏幕
        [[WSScreenShotManager shared] screenShot];
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
    //进入后台
   [[WSScreenShotManager shared] showMask];
}
- (void)applicationWillEnterForeground:(UIApplication *)application
{
    //将要进入前台
   [[WSScreenShotManager shared] hiddenMask];
}

这样就实现了切后台数据模糊处理方案。