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The Tricks to Tracing

The Tricks to Tracing

Many casual users of FreeHand MX ask how to turn a bitmap or photograph into vector art. Naturally, the hope is that there¹s a button to click and the job is done. There's not, but it's close.

Each image will be different in terms of both its content and the look you have in mind for the final artwork. That makes it pretty tough to create a cut-and-dried tutorial, but there are a few basics that you can follow.

The Trace Tool
The Trace tool is one of those areas in FreeHand where nothing is cast in stone. There are three or four main variables, and thousands more within them. There's absolutely no single-shot approach - you have to experiment. There are, however, a few points to consider when using the Trace tool. The bitmap you use should have a resolution of between 300 and 600 lines per inch. If you use a bitmap outside these limits, you'll get jaggies (on the low side) and too many points (on the high side). Higher resolution scans also take up a lot more RAM, and that can slow down your operation or even bring it to a crashing halt. A high-res tracing is a common reason that a FreeHand document won't print. You will also get different results depending on how your FreeHand Redraw preferences are set. If you have them set to Low, you will get a jaggier scan than if you set the on-screen image resolution to High or Full.

Your tracing can have color results, or grays, depending on the choice you make in the Color Mode menu (see Image I). Beyond that, you can choose from 2 (black and white) to 256 color/gray steps in RGB or CMYK. The resolution settings are Low, Normal, and High. Low will give you a looser trace in a short time; High takes longer but provides many more details and a tighter tracing. Normal is adequate for most jobs, as it splits the difference between Low and High.

The Trace tool can trace on all layers, just foreground layers, or just the background layer. Use the tool to drag a rectangular marquee over the area you wish to trace. The tool will trace everything inside the rectangle, so you can surround an entire object or trace a rectangular portion. When working with a bitmap, it's best to place the bitmap in an area that doesn't overlap any other objects when you do the tracing. For instance, if you have drawn a rectangle to surround the bitmap and it's on a foreground layer, it will become part of the tracing if you have All or Foreground selected. Moving the rectangle to the Background layer and choosing Foreground would solve the problem. You could also hide (View>Hide Selection) the rectangle until you're through with the tracing operation. At any rate, look at your layer and placement situation and make a Trace Layers choice accordingly.

Moving down the Trace tool options, you come to the Path Conversion menu. Each choice yields a totally different tracing - luckily, we have the Undo command. The Outline conversion outlines contiguous areas of color and creates closed, filled paths. You have the further options of the type of Path Overlap. If you're tracing line art or text, use None; for photographic-type images, choose Loose; and if you want a close representative of the bitmap in the tracing, pick Tight.

If your image uses a lot of strokes, and few filled areas, then Centerline is a good choice for the trace. You can choose to have Uniform, 1-point strokes, or deselect Uniform to end up with a more fluid, hand-drawn tracing.

For more ticklish drawings with strokes and filled areas, pick the Centerline/Outline conversion method. This method combines the other two methods and allows you to decide how to treat paths according to their width. Your choice is to determine that paths with widths lower than 2 to 10 points (your choice) are left open. These options may seem trivial, but make a huge difference in the resulting tracing.

The last conversion method is called Outer Edge. I call it the wire outline, and use it all the time to get a very faithful perimeter outline of my vector artwork (as long as I'm tracing closed paths). All I have to do is change the stroke width to something heavier and I'm done. I can also fill the trace with white to separate the drawing from its background, or use (without a stroke) as the basis for a drop shadow.

All that is confusing to read about, so look at Image II for a visual description. The lacy metalwork and solid areas make it a good test subject. Other than changing the Path Conversion option, none of the settings were modified. Notice the loss of detail from Outline to Centerline, and the addition of black to the Centerline/Outline methods. A second tracing using Outer Edge was made of the Outline tracing. Then it was sent to the back (Modify>Arrange>Send to Back) and given a blue tint fill. Remember that the tracing you get consists of vector paths. Those paths are fully editable, and are in every way just as if you had drawn them yourself.

So much for a relatively good trace, but if you're looking for clip art or a different feel to the artwork, try adding strokes and changing colors in the Object panel as seen in Image III. For this approach, the Name All Colors Xtra was invoked (on the 4-color gray tracing), adding three grays to the Swatches panel (with black already in the Swatches panel). Then create new colors in the Mixer panel and add them to the Swatches panel. Open Edit>Find & Replace, and select the dominant menu color within the tracing. In this case, it was the middle gray. Add a stroke (I added a black 1-point stroke), and change the fill color to something new. Here, I chose a yellow-orange tone. Then using Find & Replace again, select another gray in the image (here, the light gray). This time, I gave it a Hairline (0.25-point) stroke and a lighter fill color. Finally, I traced the image using the Outer Edge conversion method, applied a heavy stroke, and sent it to the back.

Uses of the Trace Tool
With a basic understanding of how the Trace tool works, you can save time and put your energies into designing and drawing instead of tedious manual tracing with the Pen or Bezigon tool (think how long it would take you to trace the birdcage in Image III with the Pen tool). Tracings can be used as masks or clipping paths, and also a quick way to turn a line illustration into a compound path. When you convert line art into composite paths by tracing, you are basically doing the work of the Expand Path Xtra. The resulting object can be filled with solid color, given a gradient of some kind, or used as a clipping path.

Distortion
For this spot illustration (Image V), I found a photo of a rubber duck. Normally, this image would suffice for use on the Web or in print, but I wanted to apply the image to a child's building block. That process would involve distorting the image in a way that can't be done in FreeHand, so I had to make a bitmap-to-vector conversion. I decided to use the Trace tool to make the switch. However, the yellow color of the duck was so even that a regular tracing created too many shapes and points to make a viable vector graphic. In order to clarify all the yellow tones, there were nearly 2,500 objects in the tracing. That's overkill. Because there isn't a lot of detail in the image, I decided to do a combination of Trace tool and hand-drawing. I used the Pen tool to outline shadow areas in the yellow section, and placed the shadows on a separate layer. Still using the Pen tool, I drew the other objects, placing each on its own layer to make later alterations easier to select. (If you haven't used the shortcut, you can select everything on a layer by holding down the Option/Alt key and clicking the layer's name in the Layers panel.) Some areas, such as the eyes and bowtie, were traced with the Trace tool. The Trace tool can be dragged diagonally to trace everything within the confining rectangle, or you can pull another of its tricks out of the bag.

What tricks? Well, click the cursor on an area in a bitmap or vector object, and according to the parameters you've set in the Trace dialog box, the tool will create a selection outline. Yup, the army of marching ants will surround the clicked area. Hold down the Shift key to add to the selection. It can be the same color in a different area, or it can be a different color - whatever you click will be added to the selection. If you hold down the Option/Alt key, you will deselect a given area. It's pretty much the same as working in Fireworks or Photoshop, but not quite as predictable or consistent in its operation. Once the selection is complete, you can't just add a fill or a stroke - the ants just keep on marching around - what have you accomplished?

Well, move the cursor over any part of the selection and the cursor will display a small square beneath it. Click inside the selection, and a new option box will appear. You will be able to choose Trace Selection or Convert Selection Edge (see Image IV). The former will do a regular tracing according to the parameters you've already set in the Trace dialog box. That means as many levels of color or black and white and all the other options you've selected will be in play. When you click this option and the OK button, the tracing will proceed. On the other hand, if you choose to Convert Selection Edge, each of the areas will be selected and filled with black or white, and given a black stroke, even though you may have chosen to show 256 CMYK colors. Just for reference, clicking on just the bowtie and both eyes of the duck provided 1,189 objects with Trace Selection, and 22 objects with Convert Selection Edge using the same parameters for both scans. The upside to objectively selecting parts of a bitmap or vector graphic with the wand is that you don't have the extra parts of the image that you have when using the rectangular marquee method.

When the tracing was complete, colors were chosen with the Eyedropper tool and added to the Swatches panel. By selecting all objects on particular layers, colors were applied to the various elements. I ended up with ten colors, plus black and white. Finally, I used the Trace tool again to draw a rectangle around the duck, using the Outer Edge option. I chose to add a custom Brush stroke to the path, and sent it to the back of the layer stacking order. The default brush from FreeHand looked a little boring, so I used the Knife tool to cut the path at various intervals around the duck (see Image V).

In FreeHand, you can change the height and width of a bitmapped object, and you can rotate or skew the object, but you can't use the 3D Rotate tool, the Fisheye tool, Envelope distortion, and you can't apply the bitmap to the Perspective Grid. But we're artists, and we need to do stuff to pictures. How do we get around FreeHand's limitations? That's where turning bitmaps into vectors comes in. I created a 3D child's block with the Extrusion tool. I wanted the duck (sans brush outline) and letterforms on the sides of the block. All I had to do was place an Envelope on the duck, and adjust the corners of the envelope to fit the face of the block, as shown in Image VI. The type characters could have been extruded with the Extrusion tool, but for the purpose of this short tutorial, they started as shadow color, and were converted to paths, then applied to the block using Envelopes. Then the letterform was cloned and shifted with the keyboard arrow keys to create a small amount of depth, and the color was lightened.

Masks and Clipping Paths
To continue on with the bird train of thought I'm on, I traced a badminton birdie. By the way, all the images in this article (except the assembly illustration near the end) came from the Hemera 50,000 Photo-Objects CD set; other images can be downloaded from their site at www.hemera.com. Image VII shows the original bitmap, followed by several versions of a single scan. The scan was done with eight (gray) colors. I moved each color to its own layer. Immediately to the right of the bitmap is the scan, with a white fill and paths stroked at a quarter-point. Still working on the bird metaphor, I thought of feathers, therefore fishing flies, and I used one of the layers in the scan as a clipping path. I placed the fishhook over the birdie and Cut it (Cmd/Ctrl+X). Then I selected the layer I wanted and chose Edit>Paste Inside, and turned off all the other layers except one that I gave a light gray stroke. That looked a little too viscous for a backyard game, so I did an Undo and filled my clipping layer with black, getting a nice black and white approach appropriate for clip art. I was on a roll, so I found a good feather image and did a Paste Inside - in just the black shape, but then I added the gray-stroked layer for a little color in the bottom-right image.

More Clipping Paths
I can't get enough of birds lately, so I imported an image of an eagle. This time, I used the Trace tool in the Outer Edge mode to get a really fast outline. I placed the eagle's outline over a flag image, Cut the flag image, and pasted it inside the eagle shape (Edit > Paste Inside) as shown in Image VIII. Add a calligraphic stroke and you have instant patriotism.

Stacking Up
Depending on your settings, when a trace is created in FreeHand, it appears pretty much the same as the original object. But the actual tracing is much different when you tear it apart. This is because individual colors are placed on separate levels. Not layers, but levels. There will be one color that completely encompasses the background, even though only a small area of that color appears in the tracing. If you have traced with 256 colors, you'll have 256 levels of chunky objects stacked on top of each other - and you'll watch the image build every time you change position on the screen. There are times you may want to edit color levels, delete them, or combine them with other colors. The ostrich in Image IX was scanned in only 4 colors. To separate those colors quickly, I chose Name All Colors from the Xtras menu (keep in mind that if you have other vector graphics in the document, their colors will also be named and could confuse your editing). Then I used Find & Replace to select each of the colors, which were then grouped and sent to their own new layer. After a few minutes, each of the colors was available for editing or manipulating. On the right side of Image IX, I've separated the layers so you can see how the color levels are created. Notice that the bottom layer is a solid fill of black, and shows through holes in the dark green and other layers.

Getting Creative
Having completely exhausted bird relationships, I chose an assembly illustration that I needed to spice up for a manual. The problem with computer-generated illustration is that they usually look as if they'd been drawn on a computer - imagine that! It's an easy situation to get around, and there are a couple ways that FreeHand MX can help.

First, I had to select all the strokes in the drawing and convert them into a single compound path. This drawing was done with three or four line weights, and had been enlarged or reduced at various times, so it wasn't as simple as using the Find & Replace panel to select each of the stroke sizes, and then convert them to paths. That would take a lot of time and energy. There's also the chance that one or two paths would somehow be overlooked. But by using the Trace tool it was an easy matter of dragging the wand marquee across the drawing. I clicked the selection and chose Convert Selection Edge from the pop-up window. In just a few seconds, the entire drawing had been converted to a compound path! I was warned that there were too many points to trace at the resolution I had selected, and I took the option to trace at a lower resolution. I deleted the stroke and applied a dark blue fill color. Due to the roughness of the tracing, I had a very casual drawing style working for me (as seen in the bottom half of Image IX) compared to the "computer generated" original (top half, same image). I added a Ragged vector effect in the Object panel, with three copies. The final effect is similar to a rough pencil sketch that has been tightened up with a felt tip pen. With or without the vector effect, the drawing certainly has lost its computer generated look.

Using the same tracing technique to select all the line work and create a single compound path, you have other options that are pretty easy, but look complicated. For one thing, you can apply a gradient to the compound path so the lines fade out or blend into the background. That gradient can be a linear gradient from left to right or up and down, or a radial gradient that fades out at the terminus of the lines. It's a quick trick to apply to soften up any drawing.

Summary
The Trace tool has been overlooked for many years, and it's too bad. There are many uses for the tool that will make your job easier. As with a lot of features and tools in drawing programs, it requires a bit of experimentation, but it is certainly time worth spending.

Acknowledgments
Many thanks to John Nosal, David Spells, Peter Moody, and other engineers at Macromedia for the technical editing they provide.

More Stories By Ron Rockwell

Illustrator, designer, author, and Team Macromedia member Ron Rockwell lives and works with his wife, Yvonne, in the Pocono Mountains of Pennsylvania. Ron is MXDJ's FreeHand editor and the author of FreeHand 10 f/x & Design, and he co-authored Studio MX Bible and the Digital Photography Bible. Ron has just introduced a "Casual FreeHand" course available at www.brainstormer.org.
He has Web sites at www.nidus-corp.com and www.brainstormer.org.

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