CssRewriteUrlTransform with or without virtual directory

I am not sure to fully understand your problem, but seeing http://localhost here seems wrong. You should never use an absolute URL for your bundles.

For me CssRewriteUrlTransform works perfectly, here is how I use it:

bundles.Add(new StyleBundle("~/bundles/css").Include(
                "~/Content/css/*.css", new CssRewriteUrlTransform()));

"Bundles" is virtual.

Does this helps?

Update

I was confused with the "VirtualDir" thing, as you are talking about IIS VirtualDir, and I was thinking Bundle VirtualDir! It's true that in this case CssRewriteUrlTransform will rewrite URLs to the Host, not to the Host/VirtualDir URI.

To do that, you have to derive CssRewriteUrlTransform to make it do what you need it to. There is a good discussion here: ASP.NET MVC4 Bundling with Twitter Bootstrap

Seems the best answer is there:http://aspnetoptimization.codeplex.com/workitem/83

public class CssRewriteUrlTransformWrapper : IItemTransform
{
    public string Process(string includedVirtualPath, string input)
    {           
        return new CssRewriteUrlTransform().Process("~" + VirtualPathUtility.ToAbsolute(includedVirtualPath), input);           
    }
}

Use this class instead of CssRewriteUrlTransform

I had the same problem. This is how I fixed it:

private class ProperUrlRewrite : IItemTransform
{
    private static string RebaseUrlToAbsolute(string baseUrl, string url)
    {
        if (string.IsNullOrWhiteSpace(url) || string.IsNullOrWhiteSpace(baseUrl) || url.StartsWith("/", StringComparison.OrdinalIgnoreCase) || url.Contains(':'))
            return url;
        return VirtualPathUtility.Combine(baseUrl, url);
    }
    private static Regex UrlPattern = new Regex("url\\s*\\(['\"]?(?<url>[^)]+?)['\"]?\\)");
    public string Process(string includedVirtualPath, string input)
    {
        if (includedVirtualPath == null)
            throw new ArgumentNullException("includedVirtualPath");
        if (string.IsNullOrWhiteSpace(input))
            return input;

        string directory = VirtualPathUtility.GetDirectory(VirtualPathUtility.ToAbsolute(includedVirtualPath));
        if (!directory.EndsWith("/", StringComparison.OrdinalIgnoreCase))
            directory += "/";
        return UrlPattern.Replace(input, match => "url(" + ProperUrlRewrite.RebaseUrlToAbsolute(directory, match.Groups["url"].Value) + ")");
    }
}

I know it's far from perfect and there are plenty of edge cases where this can go wrong (I'm not sure you can parse a CSS file with a regex in the first place - though this is exactly what the original CssRewriteUrlTransform does), but so far it holds...

The 'CssRewriteUrlTransform' works just fine for applications that DOESN'T run on top of a virtual directory.

So, if your app runs on http://your-site.com/ it runs just fine, but if runs on http://your-site.com/your-app/ you'll have 404 for all your images, because the default 'CssFixRewriteUrlTransform' is referencing your images with a '/'.

Use this:

public class CssFixRewriteUrlTransform: IItemTransform {

    private static string ConvertUrlsToAbsolute(string baseUrl, string content) {
        if (string.IsNullOrWhiteSpace(content)) {
            return content;
        }
        var regex = new Regex("url\\(['\"]?(?<url>[^)]+?)['\"]?\\)");
        return regex.Replace(content, match = > string.Concat("url(", RebaseUrlToAbsolute(baseUrl, match.Groups["url"].Value), ")"));
    }

    public string Process(string includedVirtualPath, string input) {
        if (includedVirtualPath == null) {
            throw new ArgumentNullException("includedVirtualPath");
        }
        var directory = VirtualPathUtility.GetDirectory(includedVirtualPath);
        return ConvertUrlsToAbsolute(directory, input);
    }

    private static string RebaseUrlToAbsolute(string baseUrl, string url) {
        if (string.IsNullOrWhiteSpace(url) || string.IsNullOrWhiteSpace(baseUrl) || url.StartsWith("/", StringComparison.OrdinalIgnoreCase)) {
            return url;
        }
        if (!baseUrl.EndsWith("/", StringComparison.OrdinalIgnoreCase)) {
            baseUrl = string.Concat(baseUrl, "/");
        }
        return VirtualPathUtility.ToAbsolute(string.Concat(baseUrl, url));
    }
}

Note: delete all file css with .min.css, because if don't it doesn't fix.