Regex检查以.jpg、.png或.gif结尾的有效URL

(?:([^:/?#]+):)?(?://([^/?#]*))?([^?#]*\.(?:jpg|gif|png))(?:\?([^#]*))?(?:#(.*))?

这是来自的官方URI解析regexp的(稍加修改)版本 RFC 2396 . 它允许 #fragments ?querystrings 显示在文件名之后,文件名可能是您想要的,也可能不是您想要的。它还匹配任何有效域,包括 localhost

更传统的regexp可能如下所示。

^https?://(?:[a-z0-9\-]+\.)+[a-z]{2,6}(?:/[^/#?]+)+\.(?:jpg|gif|png)$
          |-------- domain -----------|--- path ---|-- extension ---|

看我的 other comment ,虽然它没有回答这个问题那么完整,但我觉得在这种情况下它可能更有用。不过,我要把这个留给你

事实上

你为什么要检查网址?这不能保证你得到的是一个形象,也不能保证你拒绝的东西 不是 图像。尝试对其执行HEAD请求,并查看其内容类型 是

通常,最好使用内置库或框架函数验证URL,而不是使用自己的正则表达式来验证—请参阅 What is the best regular expression to check if a string is a valid URL 详情请参阅。

但是,如果您热衷于这样做,请查看以下问题:

Getting parts of a URL (Regex)

(?i)\.(jpg|png|gif)$

(http(s?):)|([/|.|\w|\s])*\.(?:jpg|gif|png)

这将从该字符串中提取所有图像:

background: rgb(255, 0, 0) url(../res/img/temp/634043/original/cc3d8715eed0c.jpg) repeat fixed left top; cursor: auto;
<div id="divbg" style="background-color:#ff0000"><img id="bg" src="../res/img/temp/634043/original/cc3d8715eed0c.jpg" width="100%" height="100%" /></div>
background-image: url(../res/img/temp/634043/original/cc3d8715eed0c.png);
background: rgb(255, 0, 0) url(http://google.com/res/../img/temp/634043/original/cc3    _d8715eed0c.jpg) repeat fixed left top; cursor: auto;
background: rgb(255, 0, 0) url(https://google.com/res/../img/temp/634043/original/cc3_d8715eed0c.jpg) repeat fixed left top; cursor: auto;

在此处测试您的正则表达式: https://regex101.com/r/l2Zt7S/1

(http(s?):)([/|.|\w|\s|-])*\.(?:jpg|gif|png) 对我来说真的很好。

https://farm4.staticflickr.com/3894/15008518202_c265dfa55f_h.jpg
http://farm4.staticflickr.com/3894/15008518202_c265dfa55f_h.jpg
https://farm4.staticflickr.com/3894/15008518202-c265dfa55f-h.jpg
https://farm4.staticflickr.com/3894/15008518202.c265dfa55f.h.jpg
https://farm4.staticflickr.com/3894/15008518202_c265dfa55f_h.gif
http://farm4.staticflickr.com/3894/15008518202_c265dfa55f_h.gif
https://farm4.staticflickr.com/3894/15008518202-c265dfa55f-h.gif
https://farm4.staticflickr.com/3894/15008518202.c265dfa55f.h.gif
https://farm4.staticflickr.com/3894/15008518202_c265dfa55f_h.png
http://farm4.staticflickr.com/3894/15008518202_c265dfa55f_h.png
https://farm4.staticflickr.com/3894/15008518202-c265dfa55f-h.png
https://farm4.staticflickr.com/3894/15008518202.c265dfa55f.h.png

对照此处的URL检查此正则表达式: http://regexr.com/3g1v7

#!/usr/bin/perl

use LWP::UserAgent;

my $ua = LWP::UserAgent->new;

@ARGV = qw(http://www.example.com/logo.png);

my $response = $ua->head( $ARGV[0] );

my( $class, $type ) = split m|/|, lc $response->content_type;

print "It's an image!\n" if $class eq 'image';

如果需要检查URL,请使用可靠的库,而不是自己尝试处理所有奇怪的情况:

use URI;

my $uri = URI->new( $ARGV[0] );

my $last = ( $uri->path_segments )[-1];

my( $extension ) = $last =~ m/\.([^.]+)$/g;

print "My extension is $extension\n";

祝你好运,:)

真正地 要确定,获取给定URL的前一两个KB应该足以确定您需要了解的有关图像的所有信息。

这是 an example of how you can get that information an example of it being put to use, as a Django form field 它允许您根据图像的URL轻松验证图像的存在性、文件大小、尺寸和格式。

使用 FastImage

增加 Dan's

如果存在IP地址而不是域。

^https?://(?:[a-z0-9\-]+\.)+[a-z0-9]{2,6}(?:/[^/#?]+)+\.(?:jpg|gif|png)$

但是,对于IPv4和IPv6来说,这是可以改进的,以验证子网范围。

^((http(s?)\:\/\/|~/|/)?([\w]+:\w+@)?([a-zA-Z]{1}([\w\-]+\.)+([\w]{2,5}))(:[\d]{1,5})?((/?\w+/)+|/?)(\w+\.(jpg|png|gif))

^(?:http(s)?:\/\/)?[\w.-]+(?:\.[\w\.-]+)+[\w\-\._~:/?#[\]@!\$&'\(\)\*\+,;=.]+(?:png|jpg|jpeg|gif|svg)+$

例子-

https://itelligencegroup.com/wp-content/usermedia/de_home_teaser-box_puzzle_in_the_sun.png
http://sweetytextmessages.com/wp-content/uploads/2016/11/9-Happy-Monday-images.jpg
example.com/de_home_teaser-box_puzzle_in_the_sun.png
www.example.com/de_home_teaser-box_puzzle_in_the_sun.png
https://www.greetingseveryday.com/wp-content/uploads/2016/08/Happy-Independence-Day-Greetings-Cards-Pictures-in-Urdu-Marathi-1.jpg
http://thuglifememe.com/wp-content/uploads/2017/12/Top-Happy-tuesday-quotes-1.jpg
https://1.bp.blogspot.com/-ejYG9pr06O4/Wlhn48nx9cI/AAAAAAAAC7s/gAVN3tEV3NYiNPuE-Qpr05TpqLiG79tEQCLcBGAs/s1600/Republic-Day-2017-Wallpapers.jpg

https://www.example.com
http://www.example.com
www.example.com
example.com
http://blog.example.com
http://www.example.com/product
http://www.example.com/products?id=1&page=2
http://www.example.com#up
http://255.255.255.255
255.255.255.255
http://invalid.com/perl.cgi?key= | http://web-site.com/cgi-bin/perl.cgi?key1=value1&key2
http://www.siteabcd.com:8008

参考:参见官方go-lang图像库文档的DecodeConfig部分 here

import (
  "encoding/base64"
  "fmt"
  "image"
  "log"
  "strings"
  "net/http"

  // Package image/jpeg is not used explicitly in the code below,
  // but is imported for its initialization side-effect, which allows
  // image.Decode to understand JPEG formatted images. Uncomment these
  // two lines to also understand GIF and PNG images:
  // _ "image/gif"
  // _ "image/png"
  _ "image/jpeg"
   )

func main() {
  resp, err := http.Get("http://i.imgur.com/Peq1U1u.jpg")
  if err != nil {
      log.Fatal(err)
  }
  defer resp.Body.Close()
  data, _, err := image.Decode(resp.Body)
  if err != nil {
      log.Fatal(err)
  }
  reader := base64.NewDecoder(base64.StdEncoding, strings.NewReader(data))
  config, format, err := image.DecodeConfig(reader)
  if err != nil {
      log.Fatal(err)
  }
  fmt.Println("Width:", config.Width, "Height:", config.Height, "Format:", format)
}

这里的格式是一个字符串,表示文件格式,如jpg、png等

只是提供了一个更好的解决方案。您只需验证uri并检查格式即可:

public class IsImageUriValid
{
    private readonly string[] _supportedImageFormats =
    {
        ".jpg",
        ".gif",
        ".png"
    };

    public bool IsValid(string uri)
    {
        var isUriWellFormed = Uri.IsWellFormedUriString(uri, UriKind.Absolute);

        return isUriWellFormed && IsSupportedFormat(uri);
    }

    private bool IsSupportedFormat(string uri) => _supportedImageFormats.Any(supportedImageExtension => uri.EndsWith(supportedImageExtension));
}

    const url = "https://www.laoz.com/image.png";
    const acceptedImage = [".png", ".jpg", ".gif"];
    const extension = url.substring(url.lastIndexOf("."));
    const isValidImage = acceptedImage.find((m) => m === extension) != null;
    console.log("isValidImage", isValidImage);
    console.log("extension", extension);