[移动开发]iOS黑(灰)白化实现方案---记录

领导让调研下黑(灰)白化实现方案，自己调研了两天，根据网上资料，做下记录
只是学习过程中的记录，还是写作者牛逼🐂，参考资料会附在文章中

根据业务不一样，大致产品会有两种需求：

• 需求1：全部设置为黑白色
• 需求2：某个界面设置为黑白色

大致的实现方案：

方案一：

服务端下发所有黑(灰)图片，字体颜色支持动态下发
这个，如果是只有某个界面还好，如果是全量替换图片，工作量太大

方案二：

里面大致涉及到：image、UILabel的color、UIButton的Color、webView、Video等等

对于image，一般都是使用UIImageView去显示，因此，利用runtime里面的方法交换，让setImage:方法走自己的。
然后在私有方法里面实现对图片添加滤镜

+ (void)load {
    Method customMethod = class_getInstanceMethod([self class], @selector(setImage:));
    Method originMethod = class_getInstanceMethod([self class], @selector(gl_setImage:));
    method_exchangeImplementations(customMethod, originMethod);//方法交换
}

- (void)gl_setImage:(UIImage *)image {
  	//是否黑白化,1表示开启
    BOOL isOpenWhiteBlackModel = [[NSUserDefaults standardUserDefaults] boolForKey:@"kIsShowBlackWhiteModel"];
    if (isOpenWhiteBlackModel == 1) {
        [self gl_setImage:[self gl_grayImage:image]];
    } else {
        [self gl_setImage:image];
    }
}

- (UIImage *)gl_grayImage:(UIImage *)image {
		//UIKBSplitImageView是为了键盘
    if (image == nil || [self.superview isKindOfClass:NSClassFromString(@"UIKBSplitImageView")]) {
        return image;
    }
    
    //滤镜处理
    //CIPhotoEffectNoir黑白
    //CIPhotoEffectMono单色
    NSString *filterName = @"CIPhotoEffectMono";
    CIFilter *filter = [CIFilter filterWithName:filterName];
    CIImage *inputImage = [[CIImage alloc] initWithImage:image];
    [filter setValue:inputImage forKey:kCIInputImageKey];
    CGImageRef cgImage = [self.filterContext createCGImage:filter.outputImage fromRect:[inputImage extent]];
    UIImage *resultImg = [UIImage imageWithCGImage:cgImage];
    CGImageRelease(cgImage);
    return resultImg;
}

- (CIContext *)filterContext {
    CIContext *con = objc_getAssociatedObject(self, @selector(filterContext));
    if (!con) {
        con = [[CIContext alloc] initWithOptions:nil];
        self.filterContext = con;
    }
    return con;
}

- (void)setFilterContext:(CIContext *)filterContext {
    objc_setAssociatedObject(self, @selector(filterContext), filterContext, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

H5变灰—分类

WKWebView+blackWhiteModel.m文件：

#import "WKWebView+blackWhiteModel.h"
#import <objc/runtime.h>

@implementation WKWebView (blackWhiteModel)
+ (void)load {
    Method customMethod = class_getInstanceMethod([self class], @selector(gl_initWithFrame:configuration:));
    Method originMethod = class_getInstanceMethod([self class], @selector(initWithFrame:configuration:));
    method_exchangeImplementations(customMethod, originMethod);//方法交换
}


- (instancetype)gl_initWithFrame:(CGRect)frame configuration:(WKWebViewConfiguration *)configuration
{
    BOOL isOpenWhiteBlackModel = [[NSUserDefaults standardUserDefaults] boolForKey:@"kIsShowBlackWhiteModel"];
    if (isOpenWhiteBlackModel) {
        // js脚本
        NSString *jScript = @"var filter = '-webkit-filter:grayscale(100%);-moz-filter:grayscale(100%); -ms-filter:grayscale(100%); -o-filter:grayscale(100%) filter:grayscale(100%);';document.getElementsByTagName('html')[0].style.filter = 'grayscale(100%)';";
        // 注入
        WKUserScript *wkUScript = [[WKUserScript alloc] initWithSource:jScript injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES];
                     
        WKUserContentController *wkUController = [[WKUserContentController alloc] init];
           [wkUController addUserScript:wkUScript];
        // 配置对象
        WKWebViewConfiguration *wkWebConfig = [[WKWebViewConfiguration alloc] init];
        wkWebConfig.userContentController = wkUController;
        configuration = wkWebConfig;
        WKWebView *webView = [self gl_initWithFrame:frame configuration:configuration];
        return webView;
    }
    
    return [self gl_initWithFrame:frame configuration:configuration];
}
@end

iOS APP界面黑白化处理（灰度处理）（为悼念日准备)

上述方案有个问题，因为是替换的init方法，会导致在开关为0之前的webView都是彩色、开关为1之后的webView都是灰色
因此，务必确认，请求是否开关的结果在创建webView之前，还是之后

H5变灰—单个

可以针对单个的H5做变灰处理

跟上面的js代码都一样：

    BOOL isOpenWhiteBlackModel = [[NSUserDefaults standardUserDefaults] boolForKey:@"kIsShowBlackWhiteModel"];
        
    WKWebViewConfiguration *configuration = [[WKWebViewConfiguration alloc] init];
    WKUserContentController *userController = [[WKUserContentController alloc] init];
    configuration.userContentController = userController;
    
    if (isOpenWhiteBlackModel) {
        //悼念日模式 替换wkView整体主题色
        [userController addUserScript:[self getJsStr]];
    }

-(WKUserScript *)getJsStr{
    NSString *jScript = @"var filter = '-webkit-filter:grayscale(100%);-moz-filter:grayscale(100%); -ms-filter:grayscale(100%); -o-filter:grayscale(100%) filter:grayscale(100%);';document.getElementsByTagName('html')[0].style.filter = 'grayscale(100%)';";
    // 注入
    WKUserScript *wkUScript = [[WKUserScript alloc] initWithSource:jScript injectionTime:WKUserScriptInjectionTimeAtDocumentEnd forMainFrameOnly:YES];
    return wkUScript;
}

iOS 悼念日模式

其他UILabel、UIButton等的分类可参考：

https://github.com/GeLeis/App_NoirDemo

方案三：

图片处理与方案二类似
而Label、View等的color不再一个一个做分类处理，直接修改Color的分类

+ (void)load {
    //关键方法交换
    Method customMethod = class_getClassMethod([self class], @selector(gl_colorWithRed:green:blue:alpha:));
    Method originMethod = class_getClassMethod([self class], @selector(colorWithRed:green:blue:alpha:));
    method_exchangeImplementations(customMethod, originMethod);//方法交换
}

+ (UIColor *)gl_colorWithRed:(CGFloat)red green:(CGFloat)green blue:(CGFloat)blue alpha:(CGFloat)alpha {
    //如果是单色模式(黑白模式),则平均r、g、b值
    //是否黑白化,1表示开启
    BOOL isOpenWhiteBlackModel = [[NSUserDefaults standardUserDefaults] boolForKey:@"kIsShowBlackWhiteModel"];
    if (isOpenWhiteBlackModel) {
        //r,g,b权重调整,防止出现,1 0 0 、0 1 0,0 0 1同样的结果
        //0.2126，0.7152，0.0722 这三个是根据人眼对r,g,b三个颜色面感的强弱算出来的
        CGFloat brightness = (red * 0.2126 + 0.7152 * green + 0.0722 * blue);
        return [self gl_colorWithRed:brightness green:brightness blue:brightness alpha:alpha];
    }
    return [self gl_colorWithRed:red green:green blue:blue alpha:alpha];
}

iOS 实现app黑白模式

方案四：

不再通过runtime的方法，而是直接为view添加灰色滤镜

    //获取RGBA颜色数值
   CGFloat r,g,b,a;
   [[UIColor lightGrayColor] getRed:&r green:&g blue:&b alpha:&a];
   //创建滤镜
   id cls = NSClassFromString(@"CAFilter");
   id filter = [cls filterWithName:@"colorMonochrome"];
   //设置滤镜参数
   [filter setValue:@[@(r),@(g),@(b),@(a)] forKey:@"inputColor"];
   [filter setValue:@(0) forKey:@"inputBias"];
   [filter setValue:@(1) forKey:@"inputAmount"];
   //设置给window
   self.window.layer.filters = [NSArray arrayWithObject:filter];

r, g, b, a的值都可以直接修改，而非必须是[UIColor lightGrayColor]

如果只是某个控制器A，则设置A.view.layer.filters = [NSArray arrayWithObject:filter];即可

iOS App页面置灰

当然，还有其他filter可以供使用

id cls = NSClassFromString(@"CAFilter");
id filter = [cls filterWithName:@"colorSaturate"];
[filter setValue:@(0) forKey:@"inputAmount"];
//设置给window
self.window.layer.filters = [NSArray arrayWithObject:filter];

CALayer 的 filters

其他参考文章：
iOS界面置灰方案讨论
iOS 悼念日模式
在iOS使用黑魔法实现一键全局图片变灰白的一种方案
iOS APP界面黑白化处理（灰度处理）（为悼念日准备)

CALayer 的 filters
CAFilter