UIWebView

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    //这里是js，主要目的实现对url的获取
    static  NSString * const jsGetImages =
    @"function getImages(){\
    var objs = document.getElementsByTagName(\"img\");\
    var imgScr = '';\
    for(var i=0;i<objs.length;i++){\
    imgScr = imgScr + objs[i].src + '+';\
    };\
    return imgScr;\
    };";
    
    [webView stringByEvaluatingJavaScriptFromString:jsGetImages];//注入js方法
    NSString *urlResult = [webView stringByEvaluatingJavaScriptFromString:@"getImages()"];
    NSArray *urlArray = [NSMutableArray arrayWithArray:[urlResult componentsSeparatedByString:@"+"]];
    //urlResurlt 就是获取到得所有图片的url的拼接；mUrlArray就是所有Url的数组
    NSLog(@"--%@",urlArray);
}

WKWebView

- (void)webView:(WKWebView *)webView didFinishNavigation:(null_unspecified WKNavigation *)navigation
{
    static  NSString * const jsGetImages =
    @"function getImages(){\
    var objs = document.getElementsByTagName(\"img\");\
    var imgScr = '';\
    for(var i=0;i<objs.length;i++){\
    imgScr = imgScr + objs[i].src + '+';\
    };\
    return imgScr;\
    };";
    
    [webView evaluateJavaScript:jsGetImages completionHandler:nil];
    [webView evaluateJavaScript:@"getImages()" completionHandler:^(id _Nullable result, NSError * _Nullable error) {
        
        NSArray *urlArray = [NSMutableArray arrayWithArray:[result componentsSeparatedByString:@"+"]];
        //urlResurlt 就是获取到得所有图片的url的拼接；mUrlArray就是所有Url的数组
        NSLog(@"--%@",urlArray);
    }];
}

UIWebView里图片自适应

webView.scalesPageToFit = YES;//这一句代码，貌似就适配了

- (void)webViewDidFinishLoad:(UIWebView *)webView
{
    NSString *js = @"function imgAutoFit() { \
    var imgs = document.getElementsByTagName('img'); \
    for (var i = 0; i < imgs.length; ++i) { \
    var img = imgs[i]; \
    img.style.maxWidth = %f; \
    } \
    }";

    js = [NSString stringWithFormat:js, [UIScreen mainScreen].bounds.size.width - 20];

    [webView stringByEvaluatingJavaScriptFromString:js];
    [webView stringByEvaluatingJavaScriptFromString:@"imgAutoFit()"];
}

[感谢大神]（http://www.jianshu.com/p/4523eafb4cd4）