Automated DV Uprezzing

[Bill Ravens]

I do a lot of digital still imaging via a Canon 10D. There's quite a number of sharpening algorithmns on the market, perhaps the best one is either Neatimage or FocalBlade. NeatImage is, principally, a de-noiser with sharpening technology added on. FocalBlade is a sharpener. Both pieces of software work quite well, however, they should not be applied until after uprezzing. Genuine Fractals is another very effective and interesting algorithms. Regardless of which one you pick, the per image processing time is quite long. I don't see the applicability to image sequences that are very long. At least, not with the current spate of processor technologies.

[Graeme Nattress]

The sharpening techniques in those apps look like variants on unsharp-mask techniques which produce the traditional white and black lines around "objects" in the image, and although a little can look good, doing too much can look very bad.

The techniques I'm working on are for video, but I suppose they're equally applicable to photographic enlargements, and indeed, I'm working on still frames for my initial tests... Any sharpening in my processing does not use anything remotely like unsharp-mask and does not produce the black and white outlines. In fact, the processing I'm doing is nothing like any form of traditional image processing at all - you won't find it in any text book.

As for Genuine Fractals - I've seen examples of uprezzing using their software, and examples using S-Spline, and I'm totally confident that the results I'm producing look much better that these.

As for processing times - that can be an issue, but it's going to take a couple of seconds a frame to render, and that's with totally un-optimzed code. And if the quality is there - who cares about such render times, especially how processor power increases almost daily.

Graeme

[Jonathon Wilson]

The native LanczosResize function in AviSynth is pretty great for uprez - as it keeps sharp lines sharp... and best of all - it's free. Much better than any kind of Bicubic in the upwards direction.

[Graeme Nattress]

Lanczos is just another interpolation filter. Neither BiCubic, Lanczos, Sinc etc. are intelligent in any way. The current push forwards in re-sizing technology is centred around an approach that is "data dependent" in that it relies in analysis of the image to produce a scaling that preserves smooth edges and lack of aliasing and jaggies that standard interpolation filters cannot. This is the area which I am currently researching, and indeed, having some good success. However, it's a long and complex route to take because, being data dependant, you must test your algorithm against many types of images to make sure that what works for one, will work for another. Indeed, my initial code worked great on organic images, but faired less well on cartoon outlines, whereas a standard interpolating approach will perform equally well with all types of images.

Graeme

[Jonathon Wilson]

Certainly... I only mention it, because the previous posts talked about the pros and cons of investing in various software... along with trying various things in photoshop (incremental bicubic uprezzing). I imagine that your software will be commercial based on your descriptions of its quality (sounds exciting!). The Lanczos in AviSynth is simply an alternative that is available right now, and can't be done natively in photoshop for people trying things without investing anything. It won't hold a candle to anything analytical or data-driven, but if all you've got is Photoshop - it's a different choice.

[Graeme Nattress]

Absolutely - the intent of my post was to inform about the current research, not just the research that I'm doing - into image uprezzing. It's only going to become more and more important as people try to take their old SD formats and make them usable in a modern HD environment.

My research is going slowly, but it's an immensely complex, interesting and often infuriating field to work in! I'll certainly keep you all informed as to my progress.

Graeme

[Bill Ravens]

Lanczos algorithms for still image printing is also available from a printing product called Qimage. Qimage is especially helpful for uprezzing still images. Mike Chaney, the author of Qimage, has a few novel and interesting different uprezzing techniques he makes available. One of the more interesting approaches attempts to sharpen images that have lost rez due to the pixel color masks native to CCD sensor masks.

[Graeme Nattress]

I read about Qimage as part of my research - it seems like a great program. Taking into account CCD masking isn't as important for people with 3CCD cameras, but it could make a big difference for 1CCD cameras. I don't know how my algorithm will cope with these differences yet as it's still in a really early stage.... If anyone has had some good success with other up-rez programs I'd be interested to know, for comparison purposes.

Graeme

[Graeme Nattress]

I've got some more tests of my uprezzing algorithm to show:

http://www.nattress.com/magic.htm

Comments, feedback appreciated.

Graeme

[Jonathon Wilson]

Very exciting stuff. Looks gorgeous to me. Will this be available anytime soon in your commercial products?

[Graeme Nattress]

Available yes, soon no... It's still very developmental, but it's finally reached the point where I can show it working on a real image. But next I have to get it working on video, optimised, tweaked, user controls, settings etc., so it's still quite a way off....

Graeme