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Making raster-based adjustments


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Making raster-based adjustments

So you know how to apply a Live Trace to a photograph in Illustrator. You also know that a Live Trace function is made up of two specific parts. Conditioning the image while it's still in pixel form, and then actually converting it into vector artwork. In this movie we'll focus specifically on the first part. So I'll start by clicking on the photograph, and I come over here, and I actually apply the Color 6 tracing preset. I move it up a little bit more towards the top of my page, and then I'll go ahead and click on this button here which allows me to open up the tracing options dialog box. Let me position that right about over here. Now, remember the trace itself is a two-step process. First, we condition the image and then we trace it. If you look at the tracing options dialog box, it's divided into two main sections.

On the left side we have something called Adjustments, and on the right side we have something called the Trace settings. The adjustment side is where all the conditioning happens to the image itself. All the trace setting is applied to when the artwork is actually converted into vectors. Another way to think of this is, Photoshop on the left, Illustrator on the right. Now the View settings here on the bottom is something you already know about. These pop ups for Raster here, and for Vector here, are the same as these two buttons that appear in the control panel. They simply control what you see here on your screen. So let's take a look at some of the settings that are here. Let me go ahead and click on the Preview button, so that I can see my changes as I make them We'll begin with the first setting here called Mode. Basically when you are working with Live Trace inside of Illustrator, you can convert artwork into Color, Gray scale or Black and White.

For example, I'm going to choose black and white for now, and you'll see that this is the same setting that happens by default when you first click on the Live Trace button. Now if you choose the black and white option, this setting here called Threshold becomes available. If you think about it, I'm asking Illustrator to take a full color image and convert it to just black and white pixels. There is a setting in Photoshop that does that. A setting called Threshold. Well, what is Threshold? If you think about Photoshop for a moment, the digital image is made up of channels. For example, in an RGB image it will be red, green and blue channels.

Or if you have a gray scale image, that also has the single channel. In fact, the channel itself was really just a simple gray scale image. So the first thing that Illustrator does when it is presented where a Live Trace for color image is it turns into a single channel. You may also know that a channel has 256 different levels of gray. But I can't do anything with those gray pixels. I need to end up with either black or white pixels. So what the Threshold setting allows me to do is it determines what kind of a gray pixels becomes white, or what type of gray pixels becomes black. You'll notice that the Threshold setting goes from one, all the way up to 255.

Wherever this slider is, that's the midpoint or the determinator between white pixels and black pixels. For example, at the default setting, which is really right in the middle. Any pixel up to this particular point here, any pixels that's completely white, or gets up to about 50% gray, will all turn into white pixels. Anything to the right of this slider will turn into black pixels. For example, if I want to see more detail, and more pixels become black in my image, I'll simply move the slider up a little bit. In doing so, I'll see more darker areas up here. If I want to see less detail, or more white areas in my trace, I'll move that slider to the left. Again, the Threshold setting only applies when you are working with black and white traces, and you'll also notice that the Threshold setting appears conveniently inside of the control panel when you have a black and white trace applied.

I am going to set this back to 128, or the default setting that it was at. Now you'll notice over here that the Palette and the Max color setting, which both applied a color, are grayed out and that's because I'm working with a Black and White trace. However, if I choose color, I'll see that Threshold is now grayed out. That it no longer applies, and I have the Palette and Max color settings now available. The Max color settings allows me to determine how many colors I want Illustrator to use in the Live Trace, and the Palette right now was set to Automatic. That means that Illustrator will automatically determine which 6 colors to use. Now this is a pop up menu, but you'll see that there is nothing else available here right now. We'll talk more about this particular Palette setting in another movie, but I can easily control the number of colors in my trace by adjusting these values. For example, if I want more detail in my artwork, I can change this for example to 12 colors, or if I want less detail, I may reduce this to about 3 colors. There is a check box here called Output Swatches, by checking that Illustrator will now take any of the colors that it had used in the Live Trace, and actually add them to my Swatches panel.

Now I have two remaining settings here for the image. The first setting is Blur. Because images themselves can have noise inside of it, or dust and scratches, a traced image may pick up on those little nuances and trace those elements as well. However, by applying a Blur to the image itself, those elements will not appear in the trace. Applying a blur to an image can also reduce the amount of detail that you see in your image. For example, by applying a Blur here of 2 full pixels, I can see that the areas here that have lots of detail have smoothed out.

Additionally, images with lots of grain inside of it could benefit from blurring upfront, to reduce the number of anchor points that are used in the trace at the end of the day. Finally there is a setting here called Resample. By checking this option right here, I had been able to change the actual resolution of my image. Now right now I'm working with a low-resolution image, 72 pixels per inch. However, if I'm working with a high-resolution photograph, like maybe 300 pixels per inch or more, I may find that tracing that can take a very long time. After all, Illustrator has lots of pixels to crunch. The funny thing is that you might be surprised to know that I actually get better tracing results from low- resolution images than high-resolution images.

If you think about it, the more pixels you have, the more room for error there is. So rather then have to go into Photoshop, and actually Resample images inside of Photoshop, you can do that right here inside of Illustrator. Now remember that every image is different. So there is no like one setting for any of these particular features here on the adjustment side of the tracing options dialog box. One of the great things about Live Trace is that it's live. And now that you know how to control the conditioning part of the Live Trace process, you are ready to start tweaking the actual tracing setting themselves.

Making raster-based adjustments
Video duration: 5m 52s 9h 42m Intermediate

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Making raster-based adjustments provides you with in-depth training on Design. Taught by Mordy Golding as part of the Illustrator CS4 Beyond the Basics

Subject:
Design
Software:
Illustrator
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