Wednesday, 13 October 2010

Using a Transparent Background in Reporting Services

While watching the Japanese Formula 1 Grand Prix on Sunday, it struck me that TV sports broadcasters make a lot of use of transparent overlays when showing scores, results, times, statistics, or whatever. In the case of the Grand Prix, the driver rankings in the world championship were displayed on a semi-transparent overlay, behind which the live footage of the race circuit could be seen.

So, naturally I started to wonder how I could achieve a similar visual effect in a Reporting Services report, like this:

Product Sales Report

My first thought was to look at the BackgroundColor property of the Tablix data region and set the Transparency level. However, when I looked at the color picker control for the property, this is what I saw:


Note that the Transparency control is disabled. It turns out you can only set a transparency level for gauges and charts in Reporting Services – not for shapes or data regions. So, I needed to find an alternative approach.

The answer I came up with was to create a semi-transparent .png graphic, and use it as the background image for the data region. I created this with PowerPoint, though of course you can use any graphics tool you like. I also used PowerPoint to find a suitable clipart image to use as the background for the report (on which the semi-transparent data region will be overlaid). In this case, I’m using the Adventure Works Cycles sample data, so a photo of a cyclist seems like a good choice.


You can take one of two approaches when it comes to sizing the semi-transparent image – you can make an extremely small image and then set the BackgroundRepeat property of the data region to Repeat, or you can make it bigger than the data region is ever likely to be and set the BackgroundRepeat property to Clip (or Repeat – it won’t matter since the image will be bigger than the data region anyway!). I found that PowerPoint tends to add some whitespace to the edge of a shape when you save it as a .png image, which showed up when repeating the background image, so I went with a large background image. Of course, had I used a more comprehensive graphics tool,  could have easily avoided this issue and got away with repeating a smaller image.

To embed the images to the report, I added them to the Images folder in the Report Data pane in Report Designer.


Then I set the BackgroundImage property of the tablix data region in which the report data is displayed, like so:


I’ve also used the semi-transparent image as the background for the report title textbox, which appears above the tablix data region.

The next challenge was to apply the cyclist image to the background of the report, and ensure that the layout of the report overlays the data neatly. If you have a small data set with a known number of records(for example, in a “top 10 products” report), then this is relatively straightforward. However, for a dataset with an unknown size, the data region will be resized dynamically, and automatic pagination may break the report into multiple pages. In my case, I want to ensure that the report title appears on all pages, and that the table of data has a suitable space above and below it on all pages.

To accomplish this, I added a page header and footer to the report and put the report title in the header. This ensures that if the report is paginated, the table on the second (and all subsequent pages) doesn’t start right at the top of the page. Similarly, the report footer ensures that there’s always a space after the table – it never goes all the way to the bottom of the page. I set the BackgroundImage of the report to the cyclist picture (clipped so it doesn’t repeat), and I set the InteractiveSize property of the report so that when viewed in the browser, the report has a maximum size that will keep the tablix well within the background image area. This was made tricky by the fact that Report Designer does not show the background image of the report in design view, so I had to preview the report and assess the right size through trial and error.

Report Designer

Obviously, the report size is optimized for interactive viewing, and though you can set the PageSize property of the report to an appropriate size for any other renderers you plan to use, my experience is that using background images and contrived layouts in reports you intend to render to a different format can result in some pretty horrible looking exported reports. One solution I have used in the past for this is to create the version that’s tailored for online viewing, and include a link to an offline version that has more conventional formatting for printing or exporting.

You can download the sample report I created from here. You’ll also need SQL Server 2008 R2 with Reporting Services (you can get the free Express edition from here) and the AdventureWorksDW2008R2 sample database (which you can get from here). Tags: ,