SmartReader is a .NET Standard 1.3 library to extract the main content of a web page, based on a port of the Readability library by Mozilla, which in turn is based on the famous original Readability library.
You can do it the standard way, by using the NuGet package.
PM> Install-Package SmartReader
There are already other similar good projects, but they don't support .NET Core and they are based on old version of Readability. The original library is already quite stable, but there are always improvement to be made. So by relying on a original library maintained by such a competent organization we can piggyback on their hard work and user base.
There are also some improvements: it returns an author and publication date, the language of the article, the featured image, a list of images and an indication of the time needed to read it.
Feel free to suggest new features.
There are mainly two ways to use the library. The first is by creating a new Reader object, with the URI as the argument, and then calling the GetArticle method to obtain the extracted Article. The second one is by using one of the static methods ParseArticle of Reader directly, to return an Article. Both ways are available also through an async method, called respectively GetArticleAsync and ParseArticleAsync.
The advantage of using an object, instead of the static method, is that it gives you the chance to set some options.
There is also the option to parse directly a String or Stream that you have obtained by some other way. This is available either with ParseArticle methods or by using the proper Reader constructor. In either case, you also need to give the original URI. It will not re-download the text, but it need the URI to make some checks and modifications on the links present on the page. If you cannot provide the original uri, you can use a fake one, like https:\\localhost.
If the extraction fails, the returned Article object will have the field IsReadable set to false.
The content of the article is unstyled, but it is wrapped in a div with the id readability-content that you can style yourself.
The library tries to detect the correct encoding of the text, if the correct tags are present in the text.
On the Article object you can call GetImagesAsync to obtain a Task for a list of Image objects, representing the images found in the extracted article. The method is async because it makes HEAD Requests, to obtain the size of the images and only returns the ones that are bigger then the specified size. The size by default is 75KB.
This is to exclude things such as images used in the UI.
You can customize the regular expressions that are used to determine whether a part of the document will be inside the article. There are two methods to do this:
voidAddOptionToRegularExpression(RegularExpressions expression, string option)
Add an option (i.e., usually a class name) to the regular expression.voidReplaceRegularExpression(RegularExpressions expression, string newExpression)
Replace the selected regular expression.
The type RegularExpression is an enum that can have one of the following values, corresponding to a regular expression:
- UnlikelyCandidates
- PossibleCandidates
- Positive (increases chances to keep the element)
- Negative (decreases chances to keep the element)
- Extraneous (note: this regular expression is not used anywhere at the moment)
- Byline
- Videos
Except for the Videos regular expression they all represent values of attributes, classes, etc. of tags. You should look at the code to understand how each of the regular expression is used.
The Videos regular expression represents a domain of origin of an embedded video. Since this is a string representing a regular expression, you have to remember to escape any dot present. This option is used to determine if an embed should be maintained in the article, because people generally want to see videos. If an embed matches one of the domains of this option is maintained, otherwise it is not.
// how to add the domain example.com
AddOptionToRegularExpression(RegularExpressions.Videos, "example\.com");
The library allows the user to add custom operations. I.e., to perform arbitrary modifications to the article before is processed or it is returned to the user. A custom operation receives as argument the article (an IElement). For custom operations at the start the element is the entire document, for custom operations executed after the processing is complete the element is the article extracted.
// example of custom operation
void AddInfo(AngleSharp.Dom.IElement element)
{
// we add a paragraph to the first div we find
element.QuerySelector("div").LastElementChild.InnerHtml += "<p>Article parsed by SmartReader</p>";
}
static void RemoveElement(AngleSharp.Dom.IElement element)
{
// we remove the first element with class removeable
element.QuerySelector(".removeable")?.Remove();
}
[..]
Reader reader = // ..
// add a custom operation at the start
reader.AddCustomOperationStart(RemoveElement);
// add a custom operation at the end
reader.AddCustomOperationEnd(AddInfo);As you can see the custom operation operate on an IElement and it would normally rely on the AngleSharp API. AngleSharp is the library that SmartReader uses to parse and manipulate HTML. The API of the library follows the standard structure that you can use in JavaScript, so it is intuitive to use. If you need any help to use it, consult their documentation.
Normally the library strips all classes of the elements except for page. This is done because classes are used to govern the display of the article, but they are irrelevant to the content itself. However, there is an option to preserve other classes. This is mostly useful if you want to perform custom operations on certain elements and you need CSS classes to identify them.
You can preserve classes using the property ClassesToPreserve which is an array of class names that will be preserved. Note that this has no effect if an element that contains the class is eliminated from the extracted article. This means that the option does not maintain the element in any case, it just maintains the class if the element is kept in the extracted article.
Reader reader = // ..
// preserve the class info
reader.ClassesToPreserve = new string[] { "info" };
The class page is always kept, no matter the value you assign to this option.
Using the GetArticle method.
SmartReader.Reader sr = new SmartReader.Reader("https://arstechnica.co.uk/information-technology/2017/02/humans-must-become-cyborgs-to-survive-says-elon-musk/");
sr.Debug = true;
sr.Logger = new StringWriter();
SmartReader.Article article = sr.GetArticle();
var images = article.GetImagesAsync();
if(article.IsReadable)
{
// do something with it
}Using the ParseArticle static method.
SmartReader.Article article = SmartReader.Reader.ParseArticle("https://arstechnica.co.uk/information-technology/2017/02/humans-must-become-cyborgs-to-survive-says-elon-musk/");
if(article.IsReadable)
{
// do something with it
}intMaxElemsToParse
Max number of nodes supported by this parser.
Default: 0 (no limit)intNTopCandidates
The number of top candidates to consider when analyzing how tight the competition is among candidates.
Default: 5boolDebug
Set the Debug option. If set to true the library writes the data on Logger.
Default: falseTextWriterLogger
Where the debug data is going to be written.
Default: nullboolContinueIfNotReadable
The library tries to determine if it will find an article before actually trying to do it. This option decides whether to continue if the library heuristics fails. This value is ignored if Debug is set to true
Default: trueintCharThreshold
The minimum number of characters an article must have in order to return a result.
Default: 500
UriUri
Original UriStringTitle
TitleStringByline
Byline of the article, usually containing author and publication dateStringDir
Direction of the textStringFeaturedImage
The main image of the articleStringContent
Html content of the articleStringTextContent
The pure text of the articleStringExcerpt
A summary of the article, based on metadata or first paragraphStringLanguage
Language string (es. 'en-US')intLength
Length of the text of the articleTimeSpanTimeToRead
Average time needed to read the articleDateTime?PublicationDate
Date of publication of the articleboolIsReadable
Indicate whether we successfully find an article
It's important to be aware that the fields Byline, Author and PublicationDate are found independently of each other. So there might be some inconsistencies and unexpected data. For instance, Byline may be a string in the form "@Date by @Author" or "@Author, @Date" or any other combination used by the publication.
The TimeToRead calculation is based on the research found in Standardized Assessment of Reading Performance: The New International Reading Speed Texts IReST. It should be accurate if the article is written in one of the languages in the research, but it is just an educated guess for the others languages.
The FeaturedImage property holds the image indicated by the Open Graph or Twitter meta tags. If neither of these is present, and you called the GetImagesAsync method, it will be set with the first image found.
The demo project is a simple ASP.NET Core webpage that allows you to input an address and see the results of the library.
The console project is a Console program that allows you to see the results of the library on a random test page.
In case you want to build the Nuget package yourself you cannot use the standard nuget pack because of a bug related to .NET Core. Instaed use the dotnet pack command.
dotnet pack --configuration Release --output "..\nupkgs"
The command must be issued inside the src/SmartReader folder, otherwise it will generate nuget packages for all projects.
The project uses the Apache License.
Thanks to all the people involved.