Snapheal, to be released on Wednesday, is a photo editing app for Mac which "can do magic," at least according to MacPhun, the app's developer. In addition to the usual tweaks and minor edits allowed by vanilla entry-level photo editing software, Snapheal allows you to erase whole objects - including large ones - from your photographs. Gizmag took an advance copy of Snapheal 1.0 for a spin. Could it be magic? Judge for yourself.

Before we get onto the erase features of the app, it's worth mentioning that Snapheal includes the basic suite of photo editing tools. With it you can crop and rotate photos, as well as adjust contrast, saturation, sharpness, exposure, and apply blur. Unlike, say, iPhoto, these latter adjustments can be selectively applied to particular elements by painting the effect freehand over the desired object. There are sliders to vary the extent of the edit, and these can be adjusted after the mask is painted.

Only one effect (selected in advance) can be applied to the active mask, and the moment another effect is chosen your previous edits are locked in, with only the undo button for recourse. Caution must be exercised when applying multiple retouches to a given area, as defects and artifacts can develop.

For everyday tweaks, Mac-wielding amateur photographers may do better with iPhoto which offers more flexibility in applying and removing after-effects, though the selective retouches of Snapheal might prove useful in certain cases to users who don't have more heavy-duty editing tools to hand.

No matter. Snapheal lives or dies by the success of its erase features which, Alexander Tsepko of MacPhun told Gizmag, took over six months to develop and patent. As with retouches, erasures must be painted onto the selected object. From there, one of three Eraser Modes can be applied: Wormhole, Shapeshift or Twister. Each has a different image processing algorithm at its core, and each is designed for different situations.

Wormhole, its icon suggests, copies surrounding pixels from all directions and is designed for erasing skin blemishes or small objects. Shapeshift is designed for the removal of larger objects and seems to borrow a large amount of visual data from one particular direction. Twister is the most mysterious of the three algorithms and is designed for sky, clouds or multiple small objects.

Do the erase algorithms work? We put Snapheal through a series of increasingly taxing tasks to find out.

Task 1: Cloud removal

Removing objects overlapping the sky is a feature shown in some of MacPhun's promotional and guide videos, and so we dug out a photo from the archives with a nice blue sky with some meandering cumulus clouds. Here, I wanted to remove the foreground clouds while retaining those in the distance. I tried all the deletion algorithms just to compare, and sure enough, as recommended, twister produced the best results, largely respecting and maintaining the gradated blues of the sky.

A guide video suggests that the best results can be achieved by applying the effect multiple times, but with a bit of experimenting I found the most pleasing effect was to erase the foreground clouds all at once by painting liberally over them, and then applying a few blur retouches with a nice broad brush to clean up the odd, slight imperfection here and there.

What becomes immediately obvious is that larger erasures take time. Being CPU-intensive, the removal of several clouds at once took several minutes, and was a much slower process than the promotional videos suggest, at least on an i5 MacBook Air. In recognition of this, MacPhun has thoughtfully included a series of "amazing facts" that appear on the progress bar as the app does its work. Judging by the length of time individual facts remain on screen, it appears promotional videos have sped up the image processing sections: understandable to keep the video snappy, but probably worth mentioning. Still, the results in this test were basically flawless.

Result: success

Task 2: Fly swatting

In this flower close-up I wanted to remove a small fly. That might sound straightforward enough, but this fly is a proportionately significant object and, given the lined detail of the flower petal behind it, I was worried I might be asking too much too soon of Snapheal. The promotional video features a series of deletions on fairly plain backgrounds, but the patterning on the flower petal is actually quite complex. This case presents one of the dilemmas a Snapheal user will face: should I zoom right in on the fly and paint over it in exacting detail, without going over the lines; or would I be better to just paint a big fat blob over its general location? In this case I found the latter approach worked best, but not until I'd tried the former.

Snapheal is often a case of trial and error, but if you respect your own time, it's often worth trying the simple solution first. Reasoning that in this case Wormhole (for small objects) would work best I tried it first, but both it and Shapeshift left darkened blurs on the petal and broke up the continuity of the lines. Perhaps it was the background complexity that leant itself to Twister, but the results, again, were nearly perfect.

Result: success

Task 3: Rocks and water

Here, the visual complexity of the ripples of the watery background were of potential concern, but on this test, Snapheal quickly erased a series of small rocks (we did them one at at time) quickly and painlessly. Although I expected Twister to be the pick of the bunch, a mixture of Wormhole and Shapeshift performed best to my eyes. Because the erasures were small and quick, taking seconds rather than minutes, it was painless to use the undo feature to compare algorithms then settle on a favorite.

Result: success

Task 4: Problem people

This photograph of people on the beach poses a number of challenges, not least of which are the reflections in wet sand and the multiple background layers behind the three figures paddling in the sea. Simple Shapeshift deletions here left linear defects in the images, but as MacPhun's promotional videos point out, results can often be enhanced with a touch-up using the Clone & Stamp tool, which lets you "paint" a selected part of the image over another. Think of it as a way of effectively wallpapering over the cracks. It works, albeit unpredictably, and in this case corrects any obvious defects that appeared following the deletion of the four figures. I touched up this image in just a few minutes and the results are good, if not perfect. With more time or skill, you might do better.

Result: success, but time might be an issue for non-expert perfectionists

Task 5: One goose too many

Originally I intended to erase one or two unsightly pieces of litter, but temptation got the better of me and one of the geese had to go. It's probably fair to say that Snapheal isn't designed to erase the entire foreground subject of a photograph, but the results were surprising. Again, Shapeshift did the business, though this time I was careful to paint precisely over the goose (there's something I never thought I'd say). On first attempt, a large defect was visible where the goose's head and neck had been, as some water had been borrowed from the lower half of the photo. In this case, rather than laboriously Clone & Stamp foliage over the defect, it proved simpler and more effective to perform another Shapeshift erasure over the affected area.

Full-screen, I fancy that a plump goose-like outline can be made out, but you'd need to be looking for it and looking hard. I daresay the outline could be smoothed away with a bit of work, but it's instructive to see just how effective bold deletions from busy backgrounds can be without additional touch-up.

Result: success, though Snapheal took over ten minutes to process the first deletion

Task 6: Asking the improbable

Here, a photo of a waterfall in a garden posed an opportunity to really give Snapheal a workout. The foreground flowers overlap a waterfall, and a visually complex, sharp detail of flowers and their bladed leaves in the background. In this case, I took time to carefully mask the foreground flowers before removing with Shapeshift. The results over the waterfall itself are, again, very good, though as expected there are issues where the foreground flowers overlapped those in the background. There are flowers suspended stemlessly in front of the tree and a linear array of repeated flower heads that can only be the work of a machine. Touching up this area was beyond my skill, my efforts only making matters worse. Even so, the results are possibly good enough for casual use, particularly on smaller screens (for Instagram, say).

I have a hunch better results could have been obtained by treating the waterfall portion of the image separately from the top, and by trying different algorithms on smaller areas, but you wonder how much time you might end up investing and for what gain. It's impossible to say that Snapheal cannot do better, but here we found the limits of someone with my patience and skill.

Result: still impressive, but pushing it

Summing up

Snapheal's erasing algorithms worked surprisingly well and the majority of edits proved quick and easy. Heavier deletions require time, both for the user inputs required and the processing time involved and for reasonable everyday use, the software does hit upon limitations. I can see Snapheal fitting nicely into a budding amateur photographer's app collection. Long-term, it has the potential to become a basic one-stop editing suite with a magic power or two up its sleeve.

As it is, Snapheal strikes me as a one trick pony, but it really is a neat trick, and one that compulsive photo editors may find worth the asking price of US$19.99. It's more an app for those with an artistic bent rather than documentary photographers, but for those prepared to invest a few clock cycles in more ambitious edits, it's worth the money.

Snapheal is currently available from the iTunes App Store for the launch price of US$9.99. MacPhun says an iOS version is also planned for the not-too-distant future.

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