Do you use the IAS Viewer to view our JPEG2000 (JP2) image files at full-resolution (which we highly recommend!)? If you use a Mac running OSX, you might be having trouble. Don’t worry, there’s a solution!

It appears that a recent Java patch causes problems launching the IAS Viewer client and other Java-based software launched via Java Web Start. The update changed the location of the Java Web Start application so that the system opens the downloaded JNLP file as a text file, most likely with something called Dashcode. One of our system administrators found a solution on an Apple support discussion archive. You should only have to do this once to fix the problem:

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One of our blog readers asked about the wallpapers we post on our website for some of our released images. If you haven’t seen these, they’re linked over on the lower right of pages like this. Many different sizes are available, from 800×600 all the way up to 2560×1600 (for lucky people with ginormous monitors), so you can choose the right size for your screen resolution.

Our masterful web master creates these wallpapers for each of our weekly captioned releases (these are the images we release each week with some commentary written by the science team). He picks out an interesting area from each image and produces custom cutouts in different sizes. We provide these extra files because we think the images are so beautiful, everyone should have them on their desktop. Because they’re all done by hand, though, we unfortunately don’t have the resources to make these special products for every single image. For example, most of the 1,642 images we released in our big December PDS release don’t have wallpapers. However, you can make your own, and here’s how!
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Hey, I’ll bet you didn’t notice, but the IAS Viewer has been upgraded to version 3.1.2.

One important feature enhancement is that the auto-stretch preference is now “sticky.” You can disable auto-stretch once and for all, as indicated in the screenshots below.

With this change, you can load our images and see them in the original stretch, while still having the ability to re-stretch within higher-resolution areas.

The IAS Viewer is our preferred tool for looking at HiRISE images in full resolution. It provides excellent support for the JP2 file format and the interactive streaming protocol for JP2 which is called JPIP. It is written in Java and installs automatically in a secure “sandbox” on your computer when you visit a link to it. These links are in a section labeled “JP2 Quicklook (IAS Viewer)” on the HiRISE web site; every observation will have that on the right-hand side of the page.

We use the IAS Viewer ourselves in most cases. A prerequisite is having Java installed already on your computer; I’m pretty sure that both Microsoft Vista and Apple’s OS X do that by default, and most older versions of those operating systems do too. You can check by going to java.com and clicking on the “Do I Have Java?” link.

I have tested the IAS Viewer on a 2001-era computer (an iMac DV) with a low-speed wireless connection. Surprisingly, it worked about as good as on our work machines (dual or quad-core Macs with gigs of memory and ultra-fast Ethernet connections to nearby servers). With much older PC’s or via dial-up it may not be usable, I expect. But the bottom line is, you do not need to have the latest and greatest in computing technology to fill your screen with a steady source of high-res HiRISE pixels.

Early in the mission, our partners at NASA Ames put together a site using a Flash applet called Zoomify. They still maintain this site; however, it takes time and effort for them to keep up with our releases. Zoomify uses “tile pyramids”, or multiple copies of image data at each zoom resolution. So not only must the data be transferred, it must then be rendered into many tiles, occupying slightly more space than the original data. For that reason, they convert to JPEG, which eliminates some of the highest resolution information. Still, it may be faster because the lower resolutions are pre-rendered and the highest resolution has been decreased. Flash, like the IAS Viewer, is supported on Windows, Mac, and (x86 flavors of) Linux.

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With the color images, dynamic range becomes more important then ever before. The DRA (Dynamic Range Adjustment) options of the IAS viewer are a great boon when looking at these images.

DRA performs what image processing folks call a “stretch.” A stretch takes some range of pixel values from the file and maps it onto a new range for the screen. To take an example, consider an image that appears over-exposed: much of the information is in the upper range of pixel values and you will have trouble distinquishing any detail. If the over-exposed pixels are not completely saturated (i.e. they don’t all have the maximum value) then a stretch that reduces brightness can reveal this otherwise hidden detail.

HiRISE has a very high signal-to-noise ratio, and our targeting specialists do a very good job choosing camera settings (which they do individually for each and every image) so completely saturated pixels are very rare.

But this also means that a stretch that works well over the entire image (a global stretch) may not be the best, the optimal stretch, for any one sub-image area that you are viewing. This is where the Auto DRA function in IAS becomes critical.

The button (shown below) is located on the right-hand side of the toolbar. A single click will do a stretch based only on the pixels you are viewing. This can bring out detail in shadow–amazingly, there is enough ambient light scattering around in the thin atmosphere to illuminate those scenes (and HiRISE is sensitive enough to pick enough of it up). It can also bring out detail in bright areas of over-exposure. For the color images in particular this can make things look a whole lot better.

Another factor plays a part in this. By default, the IAS viewer performs a global DRA when the image is loaded. As seen in the screenshot below, there are areas in our image that can skew the stretch. The large red rectangle is an area where the red CCDs start imaging before the blue-green. The IRB images often will have a cyan region where one of the IR CCDs was too noisy. We have elected to keep these areas in our images.

When in a sub-area, hit the Auto DRA button and the image should be drastically improved, as you can see in this final screenshot.

DRA early and often!