Comment faire un handler d’image en asp.net mvc

 

Lors de la création d’un site web un peu compliqué ou par exemple les images se trouvent sous forme de blob dans une base de données, ou les fichiers images existent à differents endroits, et pas mal d’autre cas encore, il faut utiliser un handler d’image, qui permet d’intercepter la requete de de produire un traitement avant de rendre l’image demandée.

Avec asp.net version webforms il fallait declarer un handler, souvent une url de la forme http://www.monsite.com/image.ashx?fileName=image.gif, ou plus seo compliant http://www.monsite.com/image.ashx/image.gif (malheureusement cette forme d’url ne fonctionnant pas avec le server web de dev cassini).

Avec asp.net mvc l’idée est de faire passer toutes les requetes via le “ControllerFactory”, il faut ajouter une route de la forme :

routes.MapRoute(
    "Images"
    ,"images/{*fileName}"
    , new { controller = "Images", action = "Index" }
);

L’url peut etre de la forme http://www.monsite.com/images/image.gif, attention il ne faut pas que le repertoire images existe à la racine du site.

 

A savoir, {*imageFilename} permet d’ajouter ce que l’on veut comme nom de fichier et par exemple /folder1/folder2/image.gif

 

Le controller est codé de la manière suivante :

 

public class ImagesController : Controller
{
    public ActionResult Index(string fileName)
    {
        fileName = System.IO.Path.Combine(@"c:\images", fileName);
        var mimeType = "image/gif";
        return this.File(fileName, mimeType);
    }
}

Pour ne pas compliquer le discours, je suis parti du principe que les images se trouvent dans le repertoire c:\images et qu’il n’y a que des fichiers gif, l’interception est la combinaison du nom de fichier et son chemin.

Le problème ici est qu’il manque le type mime, voici ci dessous un petit dictionnaire qui permet de retrouver un mimeType via une extension ou vice/versa.

public static Dictionary<string, string> MIMETypeDictionary
    = new Dictionary<string, string>()
{
   {"323", "text/h323"},
   {"3gp", "video/3gpp"},
   {"3gpp", "video/3gpp"},
   {"acp", "audio/x-mei-aac"},
   {"act", "text/xml"},
   {"actproj", "text/plain"},
   {"ade", "application/msaccess"},
   {"adp", "application/msaccess"},
   {"ai", "application/postscript"},
   {"aif", "audio/aiff"},
   {"aifc", "audio/aiff"},
   {"aiff", "audio/aiff"},
   {"asf", "video/x-ms-asf"},
   {"asm", "text/plain"},
   {"asx", "video/x-ms-asf"},
   {"au", "audio/basic"},
   {"avi", "video/avi"},
   {"bmp", "image/bmp"},
   {"bwp", "application/x-bwpreview"},
   {"c", "text/plain"},
   {"cat", "application/vnd.ms-pki.seccat"},
   {"cc", "text/plain"},
   {"cdf", "application/x-cdf"},
   {"cer", "application/x-x509-ca-cert"},
   {"cod", "text/plain"},
   {"cpp", "text/plain"},
   {"crl", "application/pkix-crl"},
   {"crt", "application/x-x509-ca-cert"},
   {"cs", "text/plain"},
   {"css", "text/css"},
   {"csv", "application/vnd.ms-excel"},
   {"cxx", "text/plain"},
   {"dbs", "text/plain"},
   {"def", "text/plain"},
   {"der", "application/x-x509-ca-cert"},
   {"dib", "image/bmp"},
   {"dif", "video/x-dv"},
   {"dll", "application/x-msdownload"},
   {"doc", "application/msword"},
   {"dot", "application/msword"},
   {"dsp", "text/plain"},
   {"dsw", "text/plain"},
   {"dv", "video/x-dv"},
   {"edn", "application/vnd.adobe.edn"},
   {"eml", "message/rfc822"},
   {"eps", "application/postscript"},
   {"etd", "application/x-ebx"},
   {"etp", "text/plain"},
   {"exe", "application/x-msdownload"},
   {"ext", "text/plain"},
   {"fdf", "application/vnd.fdf"},
   {"fif", "application/fractals"},
   {"fky", "text/plain"},
   {"gif", "image/gif"},
   {"gz", "application/x-gzip"},
   {"h", "text/plain"},
   {"hpp", "text/plain"},
   {"hqx", "application/mac-binhex40"},
   {"hta", "application/hta"},
   {"htc", "text/x-component"},
   {"htm", "text/html"},
   {"html", "text/html"},
   {"htt", "text/webviewhtml"},
   {"hxx", "text/plain"},
   {"i", "text/plain"},
   {"iad", "application/x-iad"},
   {"ico", "image/x-icon"},
   {"ics", "text/calendar"},
   {"idl", "text/plain"},
   {"iii", "application/x-iphone"},
   {"inc", "text/plain"},
   {"infopathxml", "application/ms-infopath.xml"},
   {"inl", "text/plain"},
   {"ins", "application/x-internet-signup"},
   {"iqy", "text/x-ms-iqy"},
   {"isp", "application/x-internet-signup"},
   {"java", "text/java"},
   {"jnlp", "application/x-java-jnlp-file"},
   {"jpg", "image/jpeg"},
   {"jpe", "image/jpeg"},
   {"jpeg", "image/jpeg"},
   {"jfif", "image/jpeg"},
   {"jsl", "text/plain"},
   {"kci", "text/plain"},
   {"la1", "audio/x-liquid-file"},
   {"lar", "application/x-laplayer-reg"},
   {"latex", "application/x-latex"},
   {"lavs", "audio/x-liquid-secure"},
   {"lgn", "text/plain"},
   {"lmsff", "audio/x-la-lms"},
   {"lqt", "audio/x-la-lqt"},
   {"lst", "text/plain"},
   {"m1v", "video/mpeg"},
   {"m3u", "audio/mpegurl"},
   {"m4e", "video/mpeg4"},
   {"MAC", "image/x-macpaint"},
   {"mak", "text/plain"},
   {"man", "application/x-troff-man"},
   {"map", "text/plain"},
   {"mda", "application/msaccess"},
   {"mdb", "application/msaccess"},
   {"mde", "application/msaccess"},
   {"mdi", "image/vnd.ms-modi"},
   {"mfp", "application/x-shockwave-flash"},
   {"mht", "message/rfc822"},
   {"mhtml", "message/rfc822"},
   {"mid", "audio/mid"},
   {"midi", "audio/mid"},
   {"mk", "text/plain"},
   {"mnd", "audio/x-musicnet-download"},
   {"mns", "audio/x-musicnet-stream"},
   {"MP1", "audio/mp1"},
   {"mp2", "video/mpeg"},
   {"mp2v", "video/mpeg"},
   {"mp3", "audio/mpeg"},
   {"mp4", "video/mp4"},
   {"mpa", "video/mpeg"},
   {"mpe", "video/mpeg"},
   {"mpeg", "video/mpeg"},
   {"mpf", "application/vnd.ms-mediapackage"},
   {"mpg", "video/mpeg"},
   {"mpg4", "video/mp4"},
   {"mpga", "audio/rn-mpeg"},
   {"mpv2", "video/mpeg"},
   {"NMW", "application/nmwb"},
   {"nws", "message/rfc822"},
   {"odc", "text/x-ms-odc"},
   {"odh", "text/plain"},
   {"odl", "text/plain"},
   {"p10", "application/pkcs10"},
   {"p12", "application/x-pkcs12"},
   {"p7b", "application/x-pkcs7-certificates"},
   {"p7c", "application/pkcs7-mime"},
   {"p7m", "application/pkcs7-mime"},
   {"p7r", "application/x-pkcs7-certreqresp"},
   {"p7s", "application/pkcs7-signature"},
   {"PCT", "image/pict"},
   {"pdf", "application/pdf"},
   {"pdx", "application/vnd.adobe.pdx"},
   {"pfx", "application/x-pkcs12"},
   {"pic", "image/pict"},
   {"PICT", "image/pict"},
   {"pko", "application/vnd.ms-pki.pko"},
   {"png", "image/png"},
   {"pnt", "image/x-macpaint"},
   {"pntg", "image/x-macpaint"},
   {"pot", "application/vnd.ms-powerpoint"},
   {"ppa", "application/vnd.ms-powerpoint"},
   {"pps", "application/vnd.ms-powerpoint"},
   {"ppt", "application/vnd.ms-powerpoint"},
   {"prc", "text/plain"},
   {"prf", "application/pics-rules"},
   {"ps", "application/postscript"},
   {"pub", "application/vnd.ms-publisher"},
   {"pwz", "application/vnd.ms-powerpoint"},
   {"qt", "video/quicktime"},
   {"qti", "image/x-quicktime"},
   {"qtif", "image/x-quicktime"},
   {"qtl", "application/x-quicktimeplayer"},
   {"qup", "application/x-quicktimeupdater"},
   {"r1m", "application/vnd.rn-recording"},
   {"r3t", "text/vnd.rn-realtext3d"},
   {"RA", "audio/vnd.rn-realaudio"},
   {"RAM", "audio/x-pn-realaudio"},
   {"rat", "application/rat-file"},
   {"rc", "text/plain"},
   {"rc2", "text/plain"},
   {"rct", "text/plain"},
   {"rec", "application/vnd.rn-recording"},
   {"rgs", "text/plain"},
   {"rjs", "application/vnd.rn-realsystem-rjs"},
   {"rjt", "application/vnd.rn-realsystem-rjt"},
   {"RM", "application/vnd.rn-realmedia"},
   {"rmf", "application/vnd.adobe.rmf"},
   {"rmi", "audio/mid"},
   {"RMJ", "application/vnd.rn-realsystem-rmj"},
   {"RMM", "audio/x-pn-realaudio"},
   {"rms", "application/vnd.rn-realmedia-secure"},
   {"rmvb", "application/vnd.rn-realmedia-vbr"},
   {"RMX", "application/vnd.rn-realsystem-rmx"},
   {"RNX", "application/vnd.rn-realplayer"},
   {"rp", "image/vnd.rn-realpix"},
   {"RPM", "audio/x-pn-realaudio-plugin"},
   {"rqy", "text/x-ms-rqy"},
   {"rsml", "application/vnd.rn-rsml"},
   {"rt", "text/vnd.rn-realtext"},
   {"rtf", "application/msword"},
   {"rul", "text/plain"},
   {"RV", "video/vnd.rn-realvideo"},
   {"s", "text/plain"},
   {"sc2", "application/schdpl32"},
   {"scd", "application/schdpl32"},
   {"sch", "application/schdpl32"},
   {"sct", "text/scriptlet"},
   {"sd2", "audio/x-sd2"},
   {"sdp", "application/sdp"},
   {"sit", "application/x-stuffit"},
   {"slk", "application/vnd.ms-excel"},
   {"sln", "application/octet-stream"},
   {"SMI", "application/smil"},
   {"smil", "application/smil"},
   {"snd", "audio/basic"},
   {"snp", "application/msaccess"},
   {"spc", "application/x-pkcs7-certificates"},
   {"spl", "application/futuresplash"},
   {"sql", "text/plain"},
   {"srf", "text/plain"},
   {"ssm", "application/streamingmedia"},
   {"sst", "application/vnd.ms-pki.certstore"},
   {"stl", "application/vnd.ms-pki.stl"},
   {"swf", "application/x-shockwave-flash"},
   {"tab", "text/plain"},
   {"tar", "application/x-tar"},
   {"tdl", "text/xml"},
   {"tgz", "application/x-compressed"},
   {"tif", "image/tiff"},
   {"tiff", "image/tiff"},
   {"tlh", "text/plain"},
   {"tli", "text/plain"},
   {"torrent", "application/x-bittorrent"},
   {"trg", "text/plain"},
   {"txt", "text/plain"},
   {"udf", "text/plain"},
   {"udt", "text/plain"},
   {"uls", "text/iuls"},
   {"user", "text/plain"},
   {"usr", "text/plain"},
   {"vb", "text/plain"},
   {"vcf", "text/x-vcard"},
   {"vcproj", "text/plain"},
   {"viw", "text/plain"},
   {"vpg", "application/x-vpeg005"},
   {"vspscc", "text/plain"},
   {"vsscc", "text/plain"},
   {"vssscc", "text/plain"},
   {"wav", "audio/wav"},
   {"wax", "audio/x-ms-wax"},
   {"wbk", "application/msword"},
   {"wiz", "application/msword"},
   {"wm", "video/x-ms-wm"},
   {"wma", "audio/x-ms-wma"},
   {"wmd", "application/x-ms-wmd"},
   {"wmv", "video/x-ms-wmv"},
   {"wmx", "video/x-ms-wmx"},
   {"wmz", "application/x-ms-wmz"},
   {"wpl", "application/vnd.ms-wpl"},
   {"wprj", "application/webzip"},
   {"wsc", "text/scriptlet"},
   {"wvx", "video/x-ms-wvx"},
   {"XBM", "image/x-xbitmap"},
   {"xdp", "application/vnd.adobe.xdp+xml"},
   {"xfd", "application/vnd.adobe.xfd+xml"},
   {"xfdf", "application/vnd.adobe.xfdf"},
   {"xla", "application/vnd.ms-excel"},
   {"xlb", "application/vnd.ms-excel"},
   {"xlc", "application/vnd.ms-excel"},
   {"xld", "application/vnd.ms-excel"},
   {"xlk", "application/vnd.ms-excel"},
   {"xll", "application/vnd.ms-excel"},
   {"xlm", "application/vnd.ms-excel"},
   {"xls", "application/vnd.ms-excel"},
   {"xlt", "application/vnd.ms-excel"},
   {"xlv", "application/vnd.ms-excel"},
   {"xlw", "application/vnd.ms-excel"},
   {"xml", "text/xml"},
   {"xpl", "audio/scpls"},
   {"xsl", "text/xml"},
   {"z", "application/x-compress"},
   {"zip", "application/x-zip-compressed"}
  };

Le code devient alors :

public ActionResult Index(string fileName)
{
    fileName = System.IO.Path.Combine(@"c:\images", fileName);
    var ext = System.IO.Path.GetExtension(fileName);
    var mime = MIMETypeDictionary.FirstOrDefault(i => i.Key.Equals(ext, StringComparison.InvariantCultureIgnoreCase));
    return this.File(fileName, mime.Value);
}

A noter il est possible de renvoyer un tableau de byte à la place d’un fichier, d’autre part si IIS6 est utilisé pour héberger le site il faut soit declarer chaque extension d’application possible par type d’image, ou ajouter un wildcard de la manière suivante :