Join Mordy Golding for an in-depth discussion in this video Understanding how Live Trace works, part of Illustrator CS4 Beyond the Basics.
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If you want to get the most out of Live Trace, it's important to realize exactly how Live Trace works, what makes it tick. Well, let's take a closer look. I have this document open. I'm simply going to click on this photograph. I'm going to click on the Live Trace button, great! I have now taken my photograph, and I have turned it into vectors. But you'll notice now that if I go ahead and I look at the image itself, I can't actually select the vector artwork, until I go ahead and I click on the Expand button. And when I do so, notice that there were not that many anchor points on here. You may have used other tools in the past, like maybe Adobe Streamline, and you know that when you've traced images using that software, you ended up with lots like millions of anchor points.
So I'm going to press Undo to go back to my Live Trace object here, and let's take a look at some of the other things that you could do with Live Trace. You'll also know that we can choose a Preset, for example, change for the color 6 preset. Well, if I already traced my artwork first into black and white, how did Illustrator know where all these colors come from? Well, to answer that question we go to the very core of why the feature is called Live Trace? It's live, because Illustrator stores to copy that image inside of the file. Now when I go ahead and I trace the artwork, and I've converted from pixels into vectors, Illustrator doesn't get rid of the image, it keeps the image, and that allows me to make changes. So it's called Live Trace, because the photograph and the vectors are tied together which really allows me to go ahead and make change this to either of them. Either the pixel based artwork, or the vector based artwork. In fact, you can see a lot of this happening directly here inside of Illustrator. You'll notice that as you've traced the object, and you have that Live Trace applied, if you look at your control panel there are these two triangles that appear here.
The one on the left is a triangle with these jagged edges, and the one on the right is basically a triangle made up of these anchor points. Both of these buttons actually control what you see on your screen. For example, a few moments ago I had a photograph on my page. I clicked the Live Trace button and chose the Color 6 preset, and now I see what that artwork looks like when converted into vector artwork, and I see that because of the settings that are contained inside of these two buttons. The button on the left, the one with jagged edges, controls the preview setting for the pixel-based artwork. The button on the right controls the preview settings for the vector based artwork.
In other words, the trace. So let's take a look at what we have here. If I click on the Preview settings for the image, I see that right now it would set to No image. Obviously, once I go ahead and I actually apply the Live Trace, Illustrator doesn't want to show me what the image looks like any more, it wants to show me what the trace looks like. So it turns the preview of the image off. Likewise, if I click now on the preview for the vector artwork, I see that it sets a tracing result. Let me go ahead and change that to No tracing result. So what I see right now on my screen is nothing. I don't see the original image, nor do I see the trace result. So let's go back over here to the image settings, and let's change that to original image. Remember, Illustrator never got rid of the photograph. It's still here inside of my file, and Illustrator is using this image in order to trace it. Now if you think about it, I have a preset set here that's set to Color 6. That means it's using 6 different colors to convert this photograph, which has millions of colors into it, into vector artwork.
Now how does Illustrator reduce the number of colors from millions to just 6? The answer is that Illustrator uses a color reduction algorithm. If you have ever tried saving a GIF file out of Illustrator, or even Photoshop, you may be familiar with something called the selective color method, which is commonly used when trying to reduce an image that has lots of colors into, for example, a GIF image that can only contain a maximum of 256 colors. Basically, Photoshop or Illustrator performs an analysis of the image, and finds the colors that are used most often and uses that information to reduce the number of colors in the file.
But let's take a step back here for a minute, and think about how this reduction happens here inside of Illustrator? I'm telling Illustrator that by the end of the day, I want 6 colors in this artwork. But the photograph has a million colors inside of it. So does Illustrator go ahead and convert this now into vector artwork using a million colors, and then try to find ways to reduce that to 6 colors? Well, that would take a lot of processing. Instead it's a whole lot easier for Illustrator to actually perform this color reduction while the photograph is still a photograph that hasn't been traced yet. Not only can Illustrator perform that calculation faster, the tracing result that it gets at the end of the day will be much better. In fact, you can actually see this happening inside of Illustrator. If I go to the Image Preview button again, I'm going to choose something here called Adjusted Image.
Adjusted Image is actually the photograph itself that has been reduced in colors before it was traced. In fact, you can even see some pixels here on the screen. By optimizing the image, or you can even say by conditioning the image in advance before tracing it, Illustrator can get much better results. We'll talk more about this concept in detail, when we learn more about the tracing option settings. But for now, let's explore some of the other preview options that you have. I'm going to back over to the Image Preview, and I can choose something called a Transparent Image. This can be helpful if I want to overlay the traced image on top of the actual photograph. This way I can compare the photograph to the result. I'll come now to the tracing options, and I'll go ahead and I'll choose Outlines.
So now I can see the photograph beneath, and I can see exactly where Illustrator is going to be drawing the path. Likewise, they can choose an option here called Outlines As Tracing that fills in those settings. So I now have a photograph behind it, the filled object that are there, and the paths as well. Now as long as the object itself remains a Live Traced object, I can easily change any of the traced settings, and the artwork will update accordingly. And when we actually click on the Expand button, thus Illustrator convert the artwork to path, but which can no longer be edited any more as a Live Traced object. So as we learn more and more about the Live Trace feature inside of Illustrator, it's important to get this concept clear.
Live Trace keeps your photograph and your vector artwork in the same file. You can make change this to either the vector part of the file, or the raster part of the file, and these two files are linked. So when you make a change to one of them, the other automatically updates. At this point you are ready to actually learn what those settings are.
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