C # The regular expression uses HTML to extract the image src from the webpage,

C # The regular expression uses HTML to extract the image src from the webpage,

Currently, the HoverTreeCMS project involves image processing. Based on the online case study, I wrote a method to obtain the image address in the content.

You can first look at the effect: http://tool.hovertree.com/a/zz/img/

Generally, an HTML document has many tags, such as
We can think about how to create this regular expression from the HTML tag format. First, I want to write several methods for img labels. If I ignore case sensitivity, I will list several possible causes of img labels.


You do not need to consider these labels because there is no image resource address.


These tags all have image resource addresses. In addition, they have pair quotation marks, which may be single or double quotation marks. Because quotation marks do not need to be matched at the same time, the regular expression can be written as follows: @ "] *) \ s */? \ S *>"


Because there may be other parameters between img and src, "] *? \ Bsrc \ s * = \ s * ["" ']? \ S *(? [^ \ s "" '<>] *) [^ <>] *? /? \ S *>"
/Images/pic.jpg "/>

For example, a carriage return or line break may occur. Therefore, a line break or TAB character must be included in a separate space, in addition, space, TAB, carriage return, and line feed characters cannot appear in the image address.

So the above regular expression can be changed to: @ "] *? \ Bsrc [\ s \ t \ r \ n] * = [\ s \ t \ r \ n] * ["']? [\ S \ t \ r \ n] * (? [^ \ s \ t \ r \ n "" '<>] *) [^ <>] *? /? [\ S \ t \ r \ n] *>"

The following is the class HvtHtmlImage used to obtain all image addresses in HTML:

1 using System. text. regularExpressions; 2 3 namespace HoverTree. hoverTreeFrame. hvtImage 4 {5 public class HvtHtmlImage 6 {7 // effect http://tool.hovertree.com/a/zz/img/ 8 /// <summary> 9 // get the URL of all images in HTML. 10 /// </summary> 11 /// <param name = "sHtmlText"> HTML code </param> 12 /// <returns> URL list of the image </returns> 13 public static string [] GetHvtImgUrls (string sHtmlText) 14 {15 // define a regular expression to match the img Tag 16 Regex m_hvtRegImg = new Regex (@ "] *? \ Bsrc [\ s \ t \ r \ n] * = [\ s \ t \ r \ n] * ["']? [\ S \ t \ r \ n] * (?  [^ \ s \ t \ r \ n "" '<>] *) [^ <>] *? /? [\ S \ t \ r \ n] *> ", RegexOptions. ignoreCase); 17 // reference: http://hovertree.com/hvtart/bjae/e4pya1x0.htm18 19 20 // search for matched string 21 MatchCollection matches = m_hvtRegImg.Matches (sHtmlText); 22 int m_ I = 0; 23 string [] sUrlList = new string [matches. count]; 24 25 // obtain the matching list 26 foreach (Match match in matches) 27 sUrlList [m_ I ++] = match. groups ["imgUrl"]. value; 28 return sUrlList; 29} 30} 31}

More: http://hovertree.com/hvtart/bjae/r42fdvjj.htm

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