Discrete Geometry Viewer—Image Analysis and Manipulation

Developed by Australian PhD student Shekhar Chandra at Monash University, Discrete Geometry Viewer (DGV) is an intriguing piece of software. As a general package, DGV, along with its various extensions, is a quantum mechanical toolkit and 3-D viewer for C++. It allows data visualisation via images, surface and volume plots using OpenGL, as well as rapidly developed Quantum Mechanical Simulations. It uses the Blitz++, VTK visualisation and open-source Qt libraries.

Breaking all that down, DGV allows you to do some really cool things with images, whether your interest is scientific or purely artistic. The program started out as a theoretical physics project under the moniker Quantum Mechanical Simulator, and Shekhar's main issue was in viewing the actual data, so he wrote DGV to fill the gap. As time goes on, Shekhar will be adding more of his PhD research work into DGV.

Quoting Shekhar, future advancements will include:

  • Pixel values within viewer.
  • Saving animations.
  • Python shell rather than simple console output. See my project called QPythonShell, which allows one to embed a Python shell into Qt applications.
  • More file formats.
  • More transforms, like the Number Theoretic Transforms (via my new Number Theoretic Transform C library).


Click on the Download link at the main Web site, and you'll be taken to a SourceForge page of hosted files. Under the Discrete Geometry Viewer heading, grab the latest package according to your system. Provided are x86 binary tarballs for Linux and Windows, as well as a source tarball. I went with the binary, which didn't have any dependency issues on my system and ran straight off the bat.

You can compile from source if you really want to—especially if you don't have an Intel-based machine—but the list of requirements is fairly stringent and may be a little obscure for many systems (see the project's Web site for more details).

Download and extract the tarball, and open a terminal in the new folder. To run the program, enter:

$ ./dgv


First, you need to import a picture. Any picture will do, but in terms of number crunching, something with a smaller resolution (say 800x600) and common aspect ratio (such as 4x3 or 16x9) will make things easier, as both you and the computer will end up doing a fair bit of mathematical work. Open whichever image you like with File→Open, and the image will come up on-screen. The image that appears probably will be in grayscale depending on the release version, but don't fret, it isn't necessarily going to stay that way.

Now, let's go straight to the program's coolest ability. Right-click on the image and choose Surface Plot with Image from the drop-down box. Then, wait a while. There's a lot of math to be crunched, but it will be a quick process if you're lucky. A new 3-D landscape now will be on-screen (and back in color), which can be moved and rotated in real time and viewed at any angle.

DGV Creating a 3-D Texture from a Photo of My Old Drumkit

My Old Drumkit

DGV made this amazing 3-D landscape from a picture inside my car!

Left-click and move the mouse forward and backward, and the world tilts accordingly. Move the mouse right or left, and the world spins in that direction. Hold Ctrl while moving the mouse, and the image rotates in front of you as if it were on a 2-D plane, clockwise or anti-clockwise. Hold Shift or your middle mouse button, then move the mouse, and you can physically drag the object horizontally or vertically within your screen.

If you find the default values and the landscape they spawn a little crude (or even a little subtle), right-click on the image and choose Scale Factor. Decrease the given value, and the resulting terrain becomes smaller and closer to the original image. This can be used to apply some very subtle image enhancements to great effect. Increase the given value, and the bumpiness of the terrain becomes larger and more exaggerated.

This by itself, however, is more of a gimmick to show off to your mates. At the heart of this project is its mathematics and plotting abilities, combined with techniques to manipulate images, that can result in some stunning outcomes.

Let's see this in action with something a little more traditional. Close any working project windows and start again from scratch with a basic 2-D image. With the file open, right-click on the image itself and choose Data from the drop-down box. A table of data will be made, and it's this table that is especially important.

Each cell of numbers contains information that affects any geometry or effects you generate from this table. To put it in English, if you know what you're doing, you can control the way the final image ends up manually. Let's use Fast Fourier Transformation as a working example. (For the purposes of space, we'll run with my working filename, which is whole-kit.jpg. Substitute your own file in place of it.)

Right-click on the table and choose Transform→Fourier→FFT. After a moment, a dotted grayscale picture will come on-screen in a separate window above the original image. Now, combine these two into a final image. Click Data→Operate from the above menu. In the new dialog window, choose Multiply under Operation, whole-kit.jpg under Data Source 1 and Image: FFT-whole-kit.jpg under Data Source 2. And, there's a spiffing new image! The original image will be combined with the grainy FFT image to make a look that is unique to each picture.

Example FFT Image

We've barely scratched the surface here, so it's well worth checking out Shekhar's tutorial (code.google.com/p/discrete-geometry-viewer/wiki/Home) and blog (l3mmings.blogspot.com) to understand what this program really is capable of doing (and apologies to Shekhar for any inaccuracies there may be in this article). For anyone looking to explore this very different area of image processing, DGV definitely is worth a look.

Discrete Geometry Viewer—Image Analysis and Manipulation (qcplusplus.sourceforge.net)

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