Mike Chambers has posted a comparison between the performance of AS3 arrays and the new Vectors available in Flash Player 10. The results look good: he managed a 60% speedup. This is very exciting for us at CleVR, because of the potential impact it has on the Stitcher in particular. This uses massive Arrays and lots of nested loops which seem to be just the kind of thing that would benefit from this. I haven’t had a chance to do any benchmarking of my own (hard at work on CleVR Pro) but when I do I’ll post another entry.

I’ve been trying to track down the source of a bug in the Stitcher. The issue was in the welcome screen, which has states for logging-in, creating a new account etc. The problem was that whenever the login state had been active, moving to another state would throw an error, The supplied DisplayObject must be a child of the caller. After much trial and error I worked out that it was down to the ControlBar that held the login buttons. It seems that the issue is that when Flex adds a controlbar, it doesn’t actually add it as a child of the container in which you place it. This means that when you then try to remove it, it’s in the wrong place. It seems to be related to this bug, which was apparently fixed last year. I’m going to have to produce a minimal version and see if I need to submit a bug report and/or patch.

Anyway, after changing it to use an HBox it’s working. I’ve uploaded a new version of the CleVR Stitcher with that fix and a few others. You can install it from that box in the sidebar (unless you’re reading this via the feed).

I’ve had a few people contact me to ask about how to use clevrlib to resize images with bicubic or bilinear interpolation in Flash or Flex, so I’ll give an overview of how to do this.

The InterpolatedBitmapData class adds the methods getPixelBicubic and getPixelBilinear to the BitmapData class, which allows you to fetch the colour of a point that’s not on a pixel boundary. We use this when reprojecting the source images in the CleVR Stitcher, but it can work just as well for resizing an image. Bear in mind that bicubic is a lot slower than bilinear, and the quality improvement isn’t usually worthwhile. However, you’re welcome to switch to getPixelBicubic if you need to.

The basic method I’m using here for resizing is to loop through the pixels of the output image, getting the equivalent pixels in the source image. As these are found by multiplying by the ratio between the source and output sizes, the coordinates probably won’t be integers. Using regular getPixel would require rounding, and therefore give a jagged (aliased) output. The getPixelXxx methods let you pass them a Number, which needn’t be an integer, giving a much smoother result.

The sample code below shows a way of resizing an image using this method. The InterpolatedBitmapData should be created in the same way as a BitmapData, such as by draw()ing a loader onto it. The example I’ve shown below is an Event.COMPLETE handler for a Loader. Code below the cut.
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It’s been a while since the CleVR Stitcher was updated as I’ve been working on some other important projects. I also had a much needed holiday! Today I have released a new version that fixes lots of bugs which have been reported over the past month or so. It also makes some hopefully significant improvements to the stitching algorithms. If you had problems with poor stitches in the past, then give it another try as it should do better. The improvements are mostly related to common problems in panoramas that have been shot by hand without a tripod.

Thank you everyone who submitted bug reports. They have bee very helpful. This release should fix all of the most commonly reported problems. See below for a list of updates, and important information on installing the update.
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The hotspot editor on CleVR.com has now been updated so it’s the same as the one in the new Stitcher. It looks quite similar to the old one, but it’s a rewrite done in Flex instead of Flash (if you don’t know what that means, don’t worry). It is however pretty much bug-free now: the old one could be a bit unstable at times. Now that it’s running off the same codebase as the Stitcher, any remaining bugs should be fixed quickly. As ever, comments and bug reports are appreciated.

If you haven’t tried adding hotspots to your panorama, give it a try. If you’re logged-in, you’ll find a button on the panorama page to edit them. Hotspots let you add another level of interactivity to your panoramas. You can create areas within the panorama that can be clicked to give more information or to move to another location. You can display text, images or even Flash files such as Youtube movies. Links to other locations lets you move around an area – for example, you could click on a doorway to move to a panorama inside a building or in a different room.

I’ve put up the CleVR AS3 libraries on RIAForge, where you can download them as a zip file, or use the svn repository.

The library includes a number of classes that we developed as part of the CleVR Stitcher. They include a set of matrix algebra classes, ported from the Java JAMA library. These let you do standard matrix algebra stuff, and includes support for singular value decomposition and QR decomposition.

There’s also some graphics classes. One is a subclass of BitmapData that adds bicubic and bilinear interpolation. Another is a class for calculating the histogram of an image, with methods to do histogram stretching. This gives results similar to “Auto levels” in Photoshop, or “Enhance” in iPhoto.

You will find them here. They’re released under the Creative Commons attribution licence, which basically lets you do anything with them, so long as you give credit somewhere. A link to clevr.com would usually suffice. Let me know if you have any comments, patches, or if you’re using it.

Yesterday’s update to the CleVR Stitcher has a number of new features. One of these is image enhancement for the finished panorama. This corrects under- or over-exposed images, and works in a similar way to “Auto levels” in Photoshop, or Enhance in iPhoto. See below for more details and a demo.
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For the second release of utility code from CleVR Stitcher, the Adobe AIR panoramic photo stitcher, I’m offering our InterpolatedBitmapData class.
The class adds support for bicubic and bilinear interpolation to the Actionscript BitmapData class. It adds two public methods – getPixelBilinear and getPixelBicubic. You can call these with sub-pixel coordinates and it will interpolate the RGB value for that point. This should be useful for anyone doing more complex transformations than those offered by the Matrix class. I hope it will be useful to someone. Do let me know if you’re using it. As ever, a link back to clevr.com is appreciated but not required.

Download it as part of the CleVR Actionscript Library

While developing the CleVR Stitcher, I needed to do quite a bit of linear algebra. I was disappointed to find that there was no Actionscript library out there for doing this, so I had to write my own. Rather than doing it from scratch, I decided to start with NIST’s Java Matrix library: JAMA, which is in the public domain.

For the benefit of anyone else needing to do stuff like this, I’m releasing the library. It’s not a full port, as I only implemented the stuff that I need. It does however support most regular operations for manipulating real matrices. As well as the normal algebra stuff, it includes classes for singular value decomposition and QR decomposition. I hope others find it useful. Let me know if you’re using it. A link back to clevr.com from your site would be appreciated but is not required.

Download it as part of the CleVR Actionscript Library

Update: The CleVR Stitcher can now be found at http://www.clevr.com/stitcher

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The Stitcher is the oldest part of CleVR, originally developed nearly four years ago, so it’s needing an upgrade. It was developed in Java, delivered by Web Start, a system that I’ve never been happy with. I decided that the best plan for the new version was to rewrite it from scratch. It’s a Flex-based Adobe AIR app. AIR, formerly called Apollo, is a new cross-platform runtime under development by Adobe. The first beta was released earlier this month, and it’s a joy to develop for. I’m pleased to announce the first alpha version of the new AIR-based CleVR Stitcher. You’ll need a CleVR account to use it. It’s free, and only takes a couple of minutes to sign up.

The choice for the development platform will be surprising to many people. The idea of doing computer vision and image processing in Flash sounds like madness, but the advances in Flash Player 9 make it possible. While developing the CleVR panorama viewer, it became apparent to me quite how powerful some of the new features were, and the performance improvements in the new Player have made it feasible. The current version is slower than the Java stitcher, but there’s a lot more optimisation that I can do, and it’s certainly usable.

Currently it’s missing a number of features from the Java version, most importantly the ability to repair failed stitches. However, I’ve made several improvements to the algorithms, so there should be fewer failed stitches. The repair facility will be added in a future release, as will several other useful features.

Give it a try, and let me know of any bugs that you find, and any other comments that you have.