I ran in the same issue a few months ago and just ran across this post. I was able to get around it by making my own Combres filter (FixUrlsInCSSFilter) that will read a "Base Url" value from the web.config or a database setting and apply it to all combres image urls.
Hope it helps someone out there...
combres.xml:
<combres xmlns='urn:combres'>
<filters>
<filter type="MySite.Filters.FixUrlsInCssFilter, MySite" />
</filters>
FixUrlsInCssFilter - most of this was copied from the original reflected file
public sealed class FixUrlsInCssFilter : ISingleContentFilter
{
/// <inheritdoc cref="IContentFilter.CanApplyTo" />
public bool CanApplyTo(ResourceType resourceType)
{
return resourceType == ResourceType.CSS;
}
/// <inheritdoc cref="ISingleContentFilter.TransformContent" />
public string TransformContent(ResourceSet resourceSet, Resource resource, string content)
{
string baseUrl = AppSettings.GetImageBaseUrl();
return Regex.Replace(content, @"url\((?<url>.*?)\)", match => FixUrl(resource, match, baseUrl),
RegexOptions.IgnoreCase | RegexOptions.Singleline | RegexOptions.ExplicitCapture);
}
private static string FixUrl(Resource resource, Match match, string baseUrl)
{
try
{
const string template = "url(\"{0}\")";
var url = match.Groups["url"].Value.Trim('\"', '\'');
while (url.StartsWith("../", StringComparison.Ordinal))
{
url = url.Substring(3); // skip one '../'
}
if (!baseUrl.EndsWith("/"))
baseUrl += "/";
if (baseUrl.StartsWith("http"))
{
return string.Format(CultureInfo.InvariantCulture, template, baseUrl + url);
}
else
return string.Format(CultureInfo.InvariantCulture, template, (baseUrl + url).ResolveUrl());
}
catch (Exception ex)
{
// Be lenient here, only log. After all, this is just an image in the CSS file
// and it should't be the reason to stop loading that CSS file.
EventManager.RaiseExceptionEvent("Cannot fix url " + match.Value, ex);
return match.Value;
}
}
}
#region Required to override FixUrlsInCssFilter for Combres
public static class CombresExtensionMethods
{
/// <summary>
/// Returns the relative HTTP path from a partial path starting out with a ~ character or the original URL if it's an absolute or relative URL that doesn't start with ~.
/// </summary>
public static string ResolveUrl(this string originalUrl)
{
if (string.IsNullOrEmpty(originalUrl) || IsAbsoluteUrl(originalUrl) || !originalUrl.StartsWith("~", StringComparison.Ordinal))
return originalUrl;
/*
* Fix up path for ~ root app dir directory
* VirtualPathUtility blows up if there is a
* query string, so we have to account for this.
*/
var queryStringStartIndex = originalUrl.IndexOf('?');
string result;
if (queryStringStartIndex != -1)
{
var baseUrl = originalUrl.Substring(0, queryStringStartIndex);
var queryString = originalUrl.Substring(queryStringStartIndex);
result = string.Concat(VirtualPathUtility.ToAbsolute(baseUrl), queryString);
}
else
{
result = VirtualPathUtility.ToAbsolute(originalUrl);
}
return result.StartsWith("/", StringComparison.Ordinal) ? result : "/" + result;
}
private static bool IsAbsoluteUrl(string url)
{
int indexOfSlashes = url.IndexOf("://", StringComparison.Ordinal);
int indexOfQuestionMarks = url.IndexOf("?", StringComparison.Ordinal);
/*
* This has :// but still NOT an absolute path:
* ~/path/to/page.aspx?returnurl=http://www.my.page
*/
return indexOfSlashes > -1 && (indexOfQuestionMarks < 0 || indexOfQuestionMarks > indexOfSlashes);
}
}
#endregion
AppSettings class - to retrieve the value from the web.config. I also use this to build the path for images not handled by combres...
public class AppSettings
{
/// <summary>
/// Retrieves the value for "ImageBaseUrl" if the key exists
/// </summary>
/// <returns></returns>
public static string GetImageBaseUrl()
{
string baseUrl = "";
if (ConfigurationManager.AppSettings["ImageBaseUrl"] != null)
baseUrl = ConfigurationManager.AppSettings["ImageBaseUrl"];
return baseUrl;
}
}
web.config values
<appSettings>
<add key="ImageBaseUrl" value="~/Content/Images/" /> <!--For Development-->
<add key="ImageBaseUrl" value="https://d209523005EXAMPLE.cloudfront.net/Content/Images/" /> <!--For Production-->
</appSettings>
