效果图

//利用UIWebViewDelegate实现截取网页中的图片
extension ViewController:UIWebViewDelegate{
   
    func webViewDidFinishLoad(_ webView: UIWebView) {
        
    //这个方法是获取网页中的所有图片
    //这里是js，主要目的实现对url的获取
        let getImg = "function getImages(){ " +
            "var objs = document.getElementsByTagName(\"img\");" +
            "var imgScr = '';" +
            "for(var i=0;i<objs.length;i++){" +
            "imgScr = imgScr + objs[i].src + '+';" +
            "};" +
            "return imgScr;" +
        "};"
        
        
        self.articleWebView.stringByEvaluatingJavaScript(from: getImg)
        
        
        
        let urlResurlt:String = webView.stringByEvaluatingJavaScript(from: "getImages()")!
        
        
        let arr = NSMutableArray.init(array: urlResurlt.components(separatedBy: "+"))
        
        //        print(arr)
        
        
        // 在H5页面加载完成时，注入图片点击的JS代码
        let js = "function addImgClickEvent() { " +
            "var imgs = document.getElementsByTagName('img');" +
            // 遍历所有的img标签，统一加上点击事件
            "for (var i = 0; i < imgs.length; ++i) {" +
            "var img = imgs[i];" +
            "img.onclick = function () {" +
            // 给图片添加URL scheme，以便在拦截时可能识别跳转
            "window.location.href = 'hyb-image-preview:' + this.src;" +
            "}" +
            "}" +
        "}"
        // 注入JS代码
        self.articleWebView.stringByEvaluatingJavaScript(from: js)
        
        // 执行所注入的JS
        self.articleWebView.stringByEvaluatingJavaScript(from: "addImgClickEvent();")
        
        
    }
    
    
    func webView(_ webView: UIWebView, shouldStartLoadWith request: URLRequest, navigationType: UIWebViewNavigationType) -> Bool {
        
        
        let requestString:String = (request.url?.absoluteString)!
        
        
        let scheme = "hyb-image-preview:"
        
        if requestString.hasPrefix(scheme) {
            // 获取原始图片的URL
            
            let path:String = (request.url?.absoluteString.substring(from: scheme.endIndex))!
            //            let src = request.url?.absoluteString.replacingOccurrences(of: scheme, with: "")
            //
            //            print(src)
            
            showBigImage(imageUrl: path)
            
            return false
            
        }
        
        
        return true
        
    }
    
//接收并展示图片 
    func showBigImage(imageUrl:String)   {
        

//一定要写这一句，不然只能预览一次图片
        self.bgView.isHidden = false
        
        self.view.addSubview(self.bgView)
        
        
        bgView.backgroundColor = UIColor(red:0.3 , green: 0.3, blue: 0.3, alpha: 0.7)
        
        
        
        let imageView = UIImageView(frame: CGRect(x: 0, y: SCREENW/2, width: SCREENW, height: 240))
        
        imageView.isUserInteractionEnabled = true
        
        imageView.cz_setImage(urlString:imageUrl, placeholderImage: nil)
        
        
        self.bgView.addSubview(imageView)
        
        
        self.bgView.addOnClickListener(target: self, action: #selector(closeClick))
        
        bgView.addSubview(closeBtn)  
    }
    
     //关闭图片
    
    func closeClick()  {
        
        
        self.bgView.isHidden = true
        
        
    }

    
}