Most efficient way to transfer images to a Silverlight client

Question

I have an application that shows a screen of image thumbnails, each image is around 80k and they are stored in a database. To keep response time reasonable, the appilcation displays a placeholder image when it first starts and later downloads the images from the server. I'm expecting to show around 40 images on the screen at once so that's my batch size. What's the best way to serve these images up to the client? I've got two options in mind.

1. Create an ADO.NET Data Service that exposes the Images database table to the client. The client can asynchronously request the images, one at a time, and display them as they come back from the server. I've implemented this solution and it seems to work Ok; the speed isn't great and I feel like I could utilize the Http pipe better by requesting maybe 3 images at a time.

2. Create an HttpModule on the server that looks for requests that look something like /Images/1.jpg and then reads the database and returns the requested data. On the client side I can have many Image objects whose source points to the virtual Urls on the server. My theory is that by just giving Silverlight many Urls to deal with it may be able to transfer the images more efficiently than my code in option 1.

Would either of these methods be more efficient or is there another technique for getting this done? Thanks!

Answer 1

We are doing something very similar, and we are just using an ASPX page to server them up with a query parameter of the image identifier. We are also caching the images, and the ASPX page will used the cached value if it exists. If not, we pull it from the data store, cache it, and send it down. It is working really well for us.

Answer 2

I don't know if it's more efficient, but I've accomplished a very similar task using an HTTP Handler (ashx). The handler pulls the image in from the database based on the Parameters in the uri (image ID), and then Silverlight fetches them asynchronously by setting the Source property of an Image control to the URI of the handler with the specific ID that I want in the query string. The Image control, in turn, is inside of an ItemsControl which allows me to display multiple images.

Answer 3

Have you looked at using Deep Zoom? It's very efficient about progressive image loading, and gives you a nicer user experience when the images are fully loaded.

Examples:

• Hard Rock Memorabilia site
• Deep Zoom Pix