Microsoft Seeks JPEG Standard Status for HD Photo
As predicted back in March, Microsoft moved forward today with plans to submit its HD Photo image format to the Joint Photographic Experts Group, for consideration as a formal standard. If adopted, Microsoft suggests the format be dubbed JPEG XR.
Like a "patent pending," just the move to get HD Photo considered will lend the format an extra degree of legitimacy. Besides utilizing a new and demonstrably more efficient compression scheme whose permissibility for use by Microsoft may not come under fire in court, the scheme depends upon device-specific color profiles as a way of ensuring the integrity of the original image.
Many consumer-grade digital cameras today utilize the JPEG format because it's reasonably robust, and because it utilizes sufficient compression to be able to get enough images onto the flash memory card. Besides, manufacturers tend to think, everyday consumers' eyes won't care about data loss around the edges. White, for most people, is white; and black is thus equally black.
HD Photo is at least selectively revolutionary because it endeavors not to make such assumptions. Most image quality degradation occurs during the translation process - when consumers load a JPEG file, crop it, and resave it. Or when they load it into Photoshop Elements or Paint Shop Pro or a similar imaging program, add graphics, save it, add more graphics, save it again, then reduce it to wallet size and save it yet again.
For the past few decades, profile-independent graphics formats such as JPEG rely on a "color space" that is much more oriented around a computer's ability to retain digits in memory and a monitor's ability to display the contents of memory, than the camera's ability to capture a much broader array of color.
In recent years, professional photographers and image specialists have relied instead on the TIFF format, mainly for its flexibility. First, it can compress images as little as a photographer may desire, with none at all being one option.
Second, it's extensibility allows for the inclusion of so-called EXIF data, which helps store information about the camera and its settings at the time a photograph was taken, along with the photograph. The alternative some photographers prefer is something called RAW format, which isn't actually a format at all, but a non-altered, non-compressed version of the picture the way the camera originally sees it. An imaging application such as Photoshop requires camera-specific "drivers" to be able to interpolate a RAW format image.
Today, Photoshop can make stronger efforts to maintain a TIFF image's original integrity by utilizing the EXIF data stored with that image, along with color profiles maintained by the computer's operating system. This way, the application can use sophisticated math to reinterpret the color values of an image for the display its user happens to be looking at, without actually tampering with the original file.
It's a workable, though complicated, process. HD Photo (or perhaps later, JPEG XR) would seek to simplify that somewhat through a process that's easier for the application to grasp, if more difficult for a writer to explain. It assumes there is no "general color space" or "default gamut," but rather depends entirely upon device color profiles to represent the dynamic range of color it's capable of representing or displaying.
So rather than an image being a re-blended version of a picture that was already hacked up to better fit into memory, HD Photo would give a camera the tools to represent its color space natively. No RAW formats here, though EXIF data about the camera are supported.
To do this, though, Microsoft's engineers took a big gamble by introducing the option of a color value storage format that hasn't seen much use since the 1970s: fixed-point representation.
In a typical standard format, "black" is represented as 0 and "white" or "full saturation" by some maximum value, such as 255 or 65,535 (usually two to some power minus one). But with the dynamic range of CCDs in digital cameras widening, engineers feel it should be up to the camera to decide what's "black" for it.
HD Photo creates a scale, where 0.0 is the minimum and 1.0 is the maximum. The camera determines the breadth of that scale; maybe some displays will match its dynamic range, maybe they won't, but the image integrity won't be compromised.
But that scale would usually mean that every color value is represented as fractional. Floating-point values are much more time consuming for any processor to implement. So Microsoft, perhaps for the first time in decades of its history, offers the fixed-point processing option. This way, values on the zero-to-one scale are represented as integers, and the decimal place is always presumed to be at or near the beginning of the value.
Even if HD Photo is adopted by JPEG - which is a real possibility at this point - a new JPEG XR format isn't likely to upset the balance of power among image formats. TIFF - currently championed by Adobe - isn't going away, though a successful infusion of HD Photo into the digital imaging landscape by Microsoft could bring it one step closer to parity in terms of competition. Microsoft isn't often seen in a come-from-behind position. So if it's embraced by a leading imaging standards body, it will be difficult for competitors to make the case (this time around) that Microsoft doesn't play fair.