How to Silhouette
If you’re a biologist, having an nice representative outline of your study organism is very handy, especially if it can be scaled to any size without losing sharpness, while remaining svelte enough to attach to an email. If you know your graphic formats, I’m talking about Encapsulated PostScript, or EPS, the vector graphics format that Illustrator and other drawing programs use. Unfortunately, most of us only have photos or sketches of our organisms, in a bitmapped format like TIFF or JPEG. How do we go from one to the other? In March of the Ratites, I briefly discussed how to make an EPS silhouette, but here’s the step by step version.
You’ll start in Illustrator, Freehand, or any other drawing program that has a pen tool. If you’re new to Illustrator, learning how to use the pen tool to create and edit paths is very strongly recommended: there are pen tool tutorials here, here, here, and here. Here’s a cheat sheet.
Start with a photo. Google’s Image search is good; large images are best. You’re looking for a view from the side with good strong edges. If you’re working from a fuzzy sketch or indistinct picture, print it large, color it in with a magic marker, and scan it back in. It’s also possible to find a few images and composite them together in Photoshop, as I’ve done below. (I was just at the University of Queensland, where these big ugly megapodes, called Brush Turkeys (Alectura lathami) steal food from cafeteria tables.)
File > Place the photo or scan in an Illustrator document. You may want to double-click the layer, lock it, and set its opacity to 50% if you’re planning to trace round it. If you choose the Template option when placing it, Illustrator will do exactly that for you. Create a new layer to draw on.
Choose the Pen tool, set the stroke to solid and the fill to none, and start clicking your way around the outline. Press down to drag out Bézier handles when you want a curve; you can adjust the exact curvature later. Most of your points will be curves; for the few acute or obtuse angles you can just click to make a corner point. If you make a mistake, choose Undo. When you get all the way round, click on your starting point to close the curve. It took me about five minutes to work my way around the Brush Turkey, and that was using a laptop trackpad. A mouse is far easier, and a graphics tablet better still—even a small graphics tablet, like the Wacom Graphire (look for a used older model) is a worthwhile investment if you plan on making a lot of information graphics.
Once you’ve finished the outline, switch to the Direct Selection tool, zoom in, and start adjusting the points and curves. Reposition the points, and lengthen/shorten/reposition the Bézier handles until the outline matches the photo. You don’t have to get it perfect, as the silhouette will usually be printed quite small. Use the cheat sheet or tutorials above to learn how to add and remove points and change them from curve to corner.
Hide the background layer, set the Fill to black, and check the overall look. You may find some weirdness where you’ve accidentally clicked too many times or dragged the wrong way; you can usually fix this by zooming in very close and removing unwanted points (by clicking on them with the Pen tool).
If you’re happy, save a just-in-case backup Illustrator file (with the .AI extension), delete the background layer, and use Save As to make an Illustrator EPS (probably best to make it CMYK with a black-and-white TIFF preview; if this is Greek to you, check out my handout on graphics formats). You can still edit the EPS in Illustrator, but it’s a common file type that can be understood and imported by most page layout and image editing programs. Because it’s a vector graphic, you can also resize it without changing the resolution, and the file size is a bit smaller: mine is 368K, a third the size of the original photo. Once you’ve made a few silhouettes, you’ll find a myriad of uses for them, from labelling phylogenies to tagging graphs to sprucing up your grant proposals and letterheads. Enjoy.
Many thanks to David Booth and Yvonne Eiby for chatting with me about Brush Turkeys, and to the University of Queensland’s Department of Integrative Biology (particularly Cynthia Riginos and Lyn Cook) for sponsoring my visit.