When was the last time you played with a kaleidoscope? I happened to find one in a store not long ago, and peering through its eyepiece, I could see the world around me replaced with pretty, symmetrical patterns. That's a pretty accurate description of what SymmetryMill does. It's a Flash-based tool for creating repeating raster-based patterns from images. Its paid version costs $69 per year (free demo with feature limitations).

SymmetryMill begins the process with a source image. This can be any image, and it doesn't have to have a pattern in it. Vector-based rival Seamless Studio does it the opposite way, starting you off with a blank canvas,  The free SymmetryMill account can only use the demo painting of a pixie, but the paid version lets you load any image from your computer (I used an image of a dog). The image appears in a small window that's floating on top of a repeating pattern. Somewhere on the image you'll find a small polygon officially called the "control path"–but really, that's the mirror for your kaleidoscope. Move the control path around, and the repeating pattern in the background instantly changes.

Unlike with a regular kaleidoscope, you can change the type of symmetry: SymmetryMill offers seventeen different symmetry types with names like "Glide reflection" and "Quarter-turns & mirrors." The names change the shape and size of the control path: You click the buttons and the image is instantly updated.

In general, the SymmetryMill interface feels like it was built for light-hearted experimentation. Everything is very responsive, and the image changes as you drag the control path around, resize it, change its symmetry type, or even rotate the source image. That means you can play around until you find a pattern you like.

One thing that makes repeating patterns so beautiful is how the shapes meld into each other. SymmetryMill has two Blend toolbars that let you control the level of blending (horizontal and vertical). For some symmetry types these bars are locked together, so moving the horizontal blend bar moves the vertical one too. Other types let you separately change horizontal and vertical blending for fine-grained control.

A single source image can yield dozens of completely different patterns, and picking just one can be difficult. Snapshots help: SymmetryMill lets you take a snapshot of the current pattern and keep experimenting. When you want to return to the pattern you had, just click the snapshot, and all settings revert to their saved state. You can also save and name multiple snapshots.

Finally, there's color: While your source image will often be a color image, these may not be the right colors for your resulting pattern. SymmetryMill's hue, saturation, brightness, contrast, and alpha sliders let you adjust any aspect of the color.

If you have to create patterns as part of your work, SymmetryMill is one of those rare applications that makes work feel like play. However, $69 a year is rather expensive, especially when the Seamless Studio costs just $45, and some image editing programs come with similar features built in. But SymmetryMill is easy and fun to use, and the results are surprisingly beautiful and diverse.

Note: The "Demo" button on the Product Information page takes you to the vendor's site, where you can use the latest version of this Web-based software.