Archive for the 'image processing' Category

Photo stitcher update, plus short links

Wednesday, July 22nd, 2009

First I must apologise for the lack of updates. All I can say is that I’ve been very busy. With that in mind, I am happy to announce two updates. First, and most important, is a new version of the CleVR Stitcher. I know that a lot of people have been having problem with poor stitching of some images. I’ve been having the same problems. Anyhow, I’m happy to say that this update greatly improves stitch quality. This is mainly down to improvements in focal length estimation and initial image warping. It’s amazing the difference that makes. I’ve also tweaked some thresholds and values to improve stitching in other ways. Let me know if it works for you.

In other matters, we now have short links implemented, using the domain Just look for the link on the panorama page. For example, see for an Apollo 11 panorama. These links are perfect for sharing your panoramas on Twitter. Once again, let me know what you think.

Actionscript 3 vector speedups

Thursday, September 25th, 2008

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.

Resizing Actionscript images with bicubic or bilinear interpolation

Thursday, July 10th, 2008

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.

Tucows on how to use CleVR

Tuesday, June 3rd, 2008

There’s a great article over on Tucows about how to use CleVR to create and share panoramas. In fact, I’d go as far to say that it’s better than our own documentation! Go and take a look, and if you like it then Digg the article.

CleVR Stitcher update fixes Sony support

Friday, May 23rd, 2008

The CleVR Stitcher uses EXIF tags embedded in the source images to calculate how the images should be warped before stitching. There is a hopeless lack of standardisation in these tags, so we have to use several different techniques to support photos from different camera manufacturers. Sony is the worst, as they do not provide enough information to enable us to make the calculation. This means that we have to use a different method to make an educated guess. However, a bug in the previous version of the Stitcher meant that Sony images would not stitch at all. Thanks to a bug report by user benbreeze this is now fixed. I have also fixed another bug in the self-updater. You can upgrade to the new version here.

Important CleVR Stitcher update

Saturday, May 17th, 2008

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.

New Stitcher, new AIR

Sunday, March 2nd, 2008

On Monday, Adobe AIR was officially launched. Of course, we’ve been using the beta version of AIR for the CleVR Stitcher for over six months now, but it’s good to see it go 1.0. This means that we’ve also released a new version of the Stitcher, which uses the latest version of AIR. You can install it below, using the shiny new installer badge. It will update or install AIR for you if needed.

New version of CleVR panoramic image Stitcher

Tuesday, January 15th, 2008

We’ve just released a new version of the CleVR Stitcher. This uses the new version of Adobe AIR, and also adds several features and fixes lots of bugs. If you download it, please do let me know what you think and if you have any problems with it.

CleVR Actionscript libraries now on RIAForge

Thursday, September 6th, 2007

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 would usually suffice. Let me know if you have any comments, patches, or if you’re using it.

Image enhancement with histogram stretching in Actionscript

Friday, July 27th, 2007

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.