Illustrator CS6 came out a few weeks ago.  Mostly it’s engine upgrade, with a few (I count two) artistic upgrade thrown in.  The first is allowing gradient on strokes (woohoo!); the second is an “improved” image trace.  How good is it?  I installed a trial version to find out.  The comparisons are between

  1. Live Trace of CS5
  2. Image Trace of CS6
  3. Vector Magic

I conducted two sections of tests.  The first section consists of throwing different types of image at the tracing engines.  This includes (1) simple B&W line art, (2) a Burberry pattern, (3) a clean illustration of a flute, and (4) a photograph.  The second section looks at how the engines deal with deteriorating quality of input, and re-uses the flute illustration in diminishing sizes, from 2000px in width to 500px in width.  Click on the images to expand.

Types of Image

B & W Line Art

The source image is a PNG diagram from Wikimedia Commons (indicatorbuis.png).  It’s a simple line-art diagram, with type, non-antialiased edges, and white background.

Vectorization of B&W line-art.  From left to right: (1) Source image.  (2) Using lettering presets, with small “mix px”.  (3) With fully auto option in CS6.  (4) Recommended options in Vector Magic.

Anchor points for expanded vectorization

With CS6, the fully-automated option misses thin lines (see lower right diagonal line), rounded out sharp corners (see corners of inverted U-shape at the bottom), and present inexplicable artefacts (see white space within the cross-shape).

Applying the lettering preset, with smaller minimum pixel, gave much better looking results, a pseudo-transparent background (more on this later), more fidelity to the letters — but many more anchor points on the circle.  Notably, there are few extraneous anchor points on the straight lines.

With VectorMagic, the default option does very well on the lines, less so on the lettering.  Its algorithm preserve the sharp corners, but also erroneously straightened out supposingly rounded corners.  I’m not quite sure why the lines leading out were tapered.

Burberry Pattern

The second image is a JPG of the Burberry pattern, which have significant defects on the edges and was something I expected all programs to have a hard time with.

Enlargement of Burberry pattern. Note the defects underneath the lowest black stripes.

Burberry pattern, vectorized.

That turned out to be true… to some extent.  The surprise was how VectorMagic failed abysmally on this task; no amount of fidgeting with the (limited) parameters gave results better than this.  CS6’s default didn’t do so great either.  Fidgeting with the parameters on CS5, I got something that’s visually alright, but the details still don’t work out.

Illustration – 2000 x 400px

This is the task I see most relevant to myself in using the image trace function.  The source is an illustration of flute terms I drew for Wikipedia, rasterized to 2000 pixels across.  (In the next section we’ll look at how each engine handles the same illustration, at lower resolutions.)  The edges are sharp.  The background is transparent, and there are partially transparent objects in the image.

Vectorizing a clean illustration. I optimize some parameters for CS5/CS6 engine to generate these results; within my explorations these are the best the engines could get to.

Outlines from vectorization.

CS5’s Live Trace gave questionable results, with much blurry shapes throughout, most easily seen from the confused outlines near the head (left) of the foot-joint.  Simple lines became thick-and-thin lines.  The type are not rendered particular well, even with this high resolution source.

CS6’s Image Trace did much better in terms of following lines: simple straight-lines remain simple straight lines, and circular shapes remain circular.  It did not handle type any better than CS5.  There are some missing lines (see barrel) and odd added shapes (see the black dot underneath the first key on the left).  The main defect here was with color: it somehow handles color differently than the other two engines, and not in a good way either.  The dash-lines were rendered funny; the dark gray in the center of the open keys were too dark, and I could not get it to pick up the subtle light shades of gray present on the keys or the flute (which CS5’s Live Trace did), even when expanding the colors it used by double the recommended numbers.

Results from VectorMagic looks very, very good, with no optimizing done.  Type, lines, and shapes all reproduce faithfully and economically – the outline looks just about as clean as my original vector drawing!  The colors were pretty much spot on, even with the somewhat tricky overlay dash-line between the red and blue keys.  (The only deficiency was the mis-colored embouchure hole.)  It was also the only engine that handles transparency and partial transparency – the only option in CS5/CS6 was to “ignore white”.  It’s hard to tell, but the dark gray in the middle of the keys are partially transparent, and VectorMagic picked up on that.

Photograph

In general vectorizing photographs are bad idea – they’ve always looked like machine-vectorized pictures, and with resource-hogging numbers of anchor-points to boot.   Nonetheless, to complete the evaluation, I handed a 8MP picture to each vectorizing engine.  The setting for both CS5 and CS6 were “photo high fidelity”, and likewise highest detail on VectorMagic.

Photo vectorizing.

Paths for vectorized photos

Vector Magic seems to optimize for simplicity, so it generates far less anchor points than either CS5 or CS6.  This comes at an expense of less fidelity to the photo.

While CS5 performs better than VectorMagic, vectorizing photos is where CS6’s Image Trace really shine.  Man, does it look good! Look at the brown on the side of the guitar, the tuning keys, and the gradient on the tube of the flute.  I’ve never seen such a nice result.

Quality Dependence on Source

This section compares the performance of the engines when the source resolution progressively degrades for the flute illustration above.

1000 x 200 px

At 1000 x 200 px, this is about the lowest resolution in which manual tracing can be done.  Files smaller than this would miss lines and require subjective interpretation to fill in the details.  As with above, the edges are unblended, and the background is partially transparent.

Vectorization for 1000px (1/4 resolution of 2000px above).

Paths for vectorizing from intermediate resolution source.

It is note-worthy that there are presets can have the same name in CS5 and CS6, but give very different results.  Sometimes the “same” preset give much better looking results in CS5 than CS6.  The default suggested, or expected, option is frequently not what the optimal one for the situation.  In this case, CS5 gives extraneous paths, to the tune of being unusable, whereas CS6 generally misses shapes with the same parameter.

Vector Magic, once again, does extremely well.  Its output is only marginally different from the result from a 4x higher resolution source.  The notably different parts is the fidelity loss on the type, the dash-lines between the red/blue keys, and the rightmost curve at the end of the flute.  Color me impressed.

500 x 100px

At 1/16th of the original size, the source image has text that can barely be read and lines that are no longer pixel-contiguous.  General trend from above holds: CS5 gives a mess of shapes, CS6 gives cleaner lines, and Vector Magic gets the idea across better than either of Adobe’s versions.

Low resolution vectorization.

 

(Early) Conclusion on CS6’s Trace

The tracing engine in CS6 is better than that in CS5 for all kinds of images.  It gives much more logical, clean, and faithful lines on non-photorealistic images, and sets the bar for photo-vectorization.  However, when it comes to non-photorealistic images, especially as the sources gets lower in quality, VectorMagic is still the king of the hill and probably not going out of business anytime soon.

I’m not so sure about Adobe’s claim in a feature video that CS6’s trace is simpler to use – there are similar plethora of presets to CS5, plus dozens of adjustable parameters, and the automated choices are often not the optimal one.  I remain confused by the presence of different presets in the control drop-down box and the Image Trace panel, and identically named presets behave altogether differently.

In terms of additional options, there is a new “overlapping shape” option in CS6 which I have not tried out yet.  There was an “outline” option that was new in CS6 Image Trace panel – I imagined that it searches for the boundaries between objects and strokes them.  It doesn’t do that – it just renders the shapes it find with a 1pt black stroke (identical to expand -> select all -> D (default appearance) -> / (remove fill)).

Personally, I can’t see myself relying on CS6’s trace any more than I would on CS5.  Most of the things I vectorize are relatively simple, non-photorealistic images from low-quality sources.  Being a pretty quick tracer (and armed with a tablet), most of these are 5-10 minutes effort with guaranteed clean lines in a logical structure.  That said, seeing its success with photographic images, I might try the CS6 ImageTrace for tracing complex gradients (matching them manually is painful and time-consuming).  It’s certainly not in itself a valid reason to upgrade…