ImageResizer Plugin for EPiServer v10

ImageResizer.Net Plugin for EPiServer v10 is released. ImageResizer.Plugins.EPiServerBlobReader got version 5.0.0.

"Old" NuGet package for EPiServer 9.x is updated with upper version constraint fix. Now plugin package v4.2 has upper EPiServer version set under v10 exclusive.

Note About Image Preview

That was quite "interesting" experience to realize changes in EPiServer.Web.BlobHttpHandler. This is eventually the guy who is responsible for returning Blob back to the client. A bit more details below.


First of all a bit background. Images in EPiServer EditUI gets different Url than on website "runtime". If image is /globalassets/image1.jpg then when you will ask Url.ContentUrl() in EPiServer EditUI it will become something like /episerver/cms/Content/globalassets/image1.jpg,,x_y?epieditmode=False..... Here is nothing fancy, but as far as I understand - ImageResizer (IR) does not kick in for the Urls containing commas ",". I opened GitHub issue for them. Awaiting authors response.

"Solution" (more like Workaround)

While debugging and joggling with internals and decompiled code in EPiServer.Web.BlobHttpHandler, I came to the conclusion that there are changes how handler decides what to do with requested Blob.

While ImageResizer haven't provided official reply on issue for handling urls with command ",", we have to remove ",,x_y" part from the Url to give possibility for IR to kick in and do proper image resizing even in EditUI mode.

There also have been lengthy discussions over GitHub about this issue and whether to implement it or not.

That's what I would at least expect being an editor, and developer. Using built-in templates like (Image.cshtml in AlloyTech):

@model EPiServer.Core.ContentReference
@if (Model != null)
    <img src="@Url.ContentUrl(Model)" alt="" />

I would expect that image acts properly if I apply IR commands to it. Even for instance using own helpers:

@using ImageResizer.Plugins.EPiServer

<img src="@Html.ResizeImage(Model.CurrentPage.MainImage, 100, 100)"/>  

The Issue with Unpublished Images

Unfortunately there is logic inside BlobHttpHandler that determines what to do with Blob after it's being retrieved from underlying store. Method is call ProccessBlobRequest(). I can't paste whole EPiServer source code here due to copyright issues, but snippet looks something like this (inside this ProccessBlobRequest()):

var evaluator = ServiceLocator.Current.GetInstance<IRoutableEvaluator>();  
if (content == null || !evaluator.IsRoutable(content))  
  return false;

By returning false from this method, BlobHttpHandler decides to return 404 status code for the whole Http request - resulting in File not found error.

And the issue is inside this IsRoutable() method. Request is "routable" to current content if:

  • if current content is published
  • or current context mode is Edit or Preview.

As we are removing ,,x_y segment from the Url while serving images due to lack of IR to kick-in -> we are losing ContextMode and EPiServer now thinks that context mode is Default.

As result - if image is not yet published (or you are browsing next draft of the content) - image will not be rendered in Preview.

However, sometimes I got image rendered within the same circumstances. It is pretty weird.

I'm not quite sure where exactly is the issue and even more - how to resolve this.

Anyway, 99% of cases seems to be working as expected.
Would be awesome if somebody from product team could comment on this issue. Thanks!

Happy resizing!

Wałdis Iljuczonok

Software architect, lead technologist and Visual Studio ALM & TFS evangelist, technical fellow. Focus on solution research, new technologies analysis and enterprise designing.

comments powered by Disqus