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Illustrator's Blob Brush lets you create loose, painterly images that have all the benefits of vector files. In this tutorial, we'll work from a photograph using Image Trace to create a custom color palette and delineate the values. We'll use flat color and simplified shapes to achieve the look of a multi-colored screen print. Let's get started!
For this tutorial, I'll be using a stock photo from Graphic River as a reference image. Place your photo on the Artboard, then go to Window> Image Trace to open the Image Trace panel. Click on the Advanced triangle if you don't see the additional options.
Keep the photo selected, then click the Low Color preset from the row of icons at the top of the panel (third one from the left). Alternately, choose the 16 Colors preset from the drop-down menu. Or, choose Color from the Mode drop-down menu and Limited from the Palette drop-down.
You can adjust the number of colors if you wish, but keep it fairly low. Check the Ignore White box, since you'll eventually choose your own background color. You'll notice that the actual number of colors decreases by two when you ignore white, so plan accordingly.
Once the trace is complete, click Expand in the Control Bar, or go to Object > Image Trace > Expand.
View the trace in Outline mode (Command + Y). You'll see a rectangular path framing the others. Select this path with the Direct Selection Tool (A), then go to Select > Same Fill & Stroke. Delete these paths.
Keep the trace selected, and click the New Color Group icon at the bottom of the Swatches panel. Click Convert Process to Global. If you're using Live Trace in CS4 — CS5, you can skip this step by checking Output to Swatches in the Live Trace panel. This is no longer an option with CS6's Image Trace.
I like to rearrange the swatches in the color group by color and value. That way, I can quickly choose colors that are similar without too much trial and error. You can do this simply by dragging them into place.
Now that we have our color palette, we want to convert the trace to grayscale to use as a reference for manually tracing with the Blob Brush. These are two reasons I prefer to use grayscale. First, it is easier to see the values of the shapes. When you're just looking at light and dark, you can better make a judgement about which colors to use to get shadows and highlights. Secondly, it's very hard to keep track of where you've traced when the color you're using is the same as the color underneath.
So select the expanded trace and go to Edit > Edit Color > Convert to Grayscale.
You may be wondering, why not just do a grayscale trace? If you're using Live Trace in CS4 — CS5, that's definitely an option. Simply make a copy of your trace before you expand it, then change the settings on that one to grayscale, with the same number of colors. Image Trace in CS6 seems to have a bug when it comes to specifying the number of colors in a grayscale trace. In the image below, you can see that I've specified a maximum of 20 grays, but the trace result shows 168!
The final step in preparing the source image is to put it on a template layer. But fist, it must be rasterized. Keep the grayscale objects selected, and go to Object > Rasterize. You can choose 72 ppi as the resolution, this will only be used as a reference.
The reason we need a raster object on the template layer is because of the special properties of a template layer. As you will see, when you're working with vector objects on their own layer, you can switch to Outline mode and still see the image on the template layer.
Double-click the layer in the Layers panel and click Template. You can change the name and layer color here as well. By default, Template layers are locked. Keep it locked, then create a new layer above it.
Now we're ready to paint with the Blob Brush. The interface in CS6 is slightly different, but the functionality has not changed. The following options are the same in versions CS4 and CS5. If you're already familiar with the Blob Brush, skip to Step 11.
Double-click the Blob Brush Tool to bring up its options. We'll just look at the bottom section for now, where you can adjust the Size, Angle and Roundness. Above those settings is a visual representation of the brush and its size range. So in this example, the brush size is set at 12 points, with a variation of 10 points. Thus, the size of the stroke can be 2 points, 22 points, or anything in between. Similarly, the Roundness is set at 60%, with a variation of 40%, which means it can go from 20% to 100%.
The pop-up list to the right of each option lets you further control variations in the brush. Note that these variations only work when using a graphics tablet, as a mouse does not respond to things like pressure and tilt.
These options are:
- Fixed — No variation in angle, roundness, or diameter.
- Random — Random variations in angle, roundness, or diameter.
- Pressure — Variation is based on the pressure when using a tablet and stylus. A greater pressure produces a thicker stroke, and a lighter pressure results in a thinner and more angular stroke.
- Stylus Wheel — Some airbrush pens have a stylus wheel on their barrels. That's what this option is for.
- Tilt, Bearing, and Rotation — These are available only if you have a graphics pen that can detect these types of movement, such as the Wacom 6D.
Get a feel for the Blob Brush by painting some strokes. Take a look at the Color panel. Since the Blob Brush is technically a brush, whatever stroke color you have selected will be the color the brush uses. Let's say you're using a red stroke and a blue fill. When you paint with the Blob Brush, a red stroke will result, but this "stroke" is actually a filled object. If you have only a fill color selected in the Color panel, the Blob Brush will use that.
Paint another stroke that overlaps the first, and you'll see that the new stroke merges with the first. In effect, Illustrator is performing a Pathfinder function as you draw — as long as you're still using the same stroke color as before. Try painting with another color, even one that is slightly different, and you'll see that the shapes do not merge.
Open Blob Brush Tool Options again by double-clicking on the tool. Take a look at the top half of the dialog box. Under Tolerances, you can adjust the Fidelity — how closely the brush conforms to your mouse or pen movement — and the Smoothness. Lower values will create tighter paths with more points, higher values result in looser, smoother objects.
If you check the "Keep Selected" box, that's exactly what it will do. Depending on your workflow and personal preference, you may want to have the last stroke you draw remain selected. For example, if you hold down the Option (PC: Alt) key, the Blob Brush temporarily switches to the Smooth tool.
Keeping the path selected will speed up the process of drawing then smoothing. You can also hold down the Command (PC: Control) key to temporarily switch to the Selection tools and move or adjust the paths from there.
If you choose "Merge Only with Selection," any new stroke you draw will merge only with a path that's selected. The exception to this rule is if the merging would interfere with the stacking order of the objects.
If you check both boxes, you get both behaviors. NOTE: "Merge Only with Selection" in CS5 is called "Selection Limits Merge" In CS4. The functions for each are the same.
Start painting the front-most pepper using a bright red. Paint around the edges of the pepper shape. This will result in a hollow, compound path. You can now select the inner path with the Direct Selection tool and delete it. You could also just fill in the center with the Blob Brush, but I think this is slightly faster.
For the darker parts of the pepper, follow the contours of the reference photo and paint them on top of the main pepper shape. Make the outer edges of the shapes overlap, then remove the excess with the Shape Builder tool. To remove an overlapping section, hold down the Option/Alt key while dragging over it with the tool.
For greater color harmony, use the same color as the main pepper shape for the darker values. Change the blending mode to Multiply and adjust the opacity if desired.
For the highlights, use a lighter red from the color group. Since these are Global colors, you can also adjust the tint of the highlights if desired.
Draw the stem in the same way, using greens instead of reds, of course. Create a new layer below the first pepper layer and paint the chile pepper on the right. Pay attention to the shadow cast on this pepper by the first one. Use the darkest red swatch and Multiply blending mode.
Create a new layer for the middle chile pepper. You don't have to have a separate layer for each piece of the still life, but I find it helps isolate each part, making them easier to work on.
Paint the third chile pepper in the same fashion. If you view the illustration in Outline mode, you can check your painting against the source image.
Depending on your settings in the Blob Brush tool options, you may find that your paths have a few too many points. You can smooth them out by holding the Option/Alt key while using the Blob Brush, which will temporarily change to the Smooth tool.
You can also go to Object > Path > Simplify. Set a fairly high percentage in the Curve Precision field, which will maintain the overall shape, but get rid of some of the extra points.
Continue building the illustration piece by piece. Working quickly with the Blob Brush will give you a looser look that can be cleaned up quickly using the Shape Builder tool and the Simplify function. In fact, it's a good idea to create an Action for your Simplify settings and assign a hotkey to it. Then you can paint a stroke, then clean it up with the press of a button.
Keep the colors consistent using the blending modes and transparency. Check the values (not the hues) against the grayscale trace. You'll be surprised how a few abstract shapes will come together as a pepper or leaf, once the values and colors are applied to them.
Below are some process shots of the peppers and the pot:
The leaves are constructed in the same way as the peppers. Just because you're working from a photograph, doesn't mean you have to draw every single leaf, stem and vein. Be judicious. A good rule of thumb, however, is that more detailed objects will draw attention to themselves, so use more detail on the leaves in front, and keep the ones in back simpler.
In addition to using the Multiply mode for darker areas, try using Screen mode for lighter areas. As before, this will ensure color consistency, and enhance the screen print look.
Below are some examples of how to build the leaves.
For the stems, create a new layer below the leaves. Work quickly, adding darker blobs where shadows fall.
Choose a background color. It is fun to try out different colors using the Color Guide panel. Select a swatch in the Swatches panel, then you can see many color combinations based on that swatch.
Draw the shadow with the same color, changing its blending mode to Multiply. Since this is a vector illustration, of course, you can change colors to your heart's content.
Live Trace/Image Trace are impressive tools, but an unaltered trace is rarely satisfactory as the final result. It may seem like a lot of work to create an image like this by hand, but the result is more organic in appearance. And spending some time up front to set up and organize your file will make the rest of the work a breeze.