- [Voiceover] In this movie, I'll show you
how to customize the autotracing effect,
specifically using an option known as threshold,
which is gonna allow us to preserve
some of the more fragile details in the original lineart.
So I'm gonna go ahead and zoom in here,
and I'll click on the image to select it.
And then I'll go up here to the Options bar,
and there's this little icon that says Image Trace panel.
If you click on it, you'll bring up the panel like so.
You can also go to the Window menu, by the way,
and choose Image Trace if you like.
After all, you can get to all of the panels
in Illustrator from the Window menu.
I'm gonna go ahead and move this guy
off over to the side by dragging it
from the upper left corner,
so I don't accidentally drop it into the other panels.
Alright, now I want you to notice this View option.
Right now we're seeing the tracing results,
and that is, we're seeing the traced path outlines.
If you wanna see the outlines instead,
you can choose outlines
and that'll give you the cyan outlines,
which are of some benefit, I suppose.
Or you can switch to the source image
so that you're seeing the original pixel-based image
as it appears before Illustrator traces it.
Ideally, what you wanna be able to do
is compare the original image to the tracing result,
and the easiest way to do that
is to click and hold on this eye icon right there.
So if you click and hold, you'll see
the original pixel based image.
If you release, you'll see the tracing.
And what that's gonna help you decide is
how much of the image is missing
in the final traced result.
So for example, look at the lines inside my eye.
If I click and hold, they're a lot more clear.
We have some thin lines that are there
to indicate wrinkling, I suppose,
even though I was only in my twenties.
And then if I release, a lot of those lines disappear,
especially the ones inside Saturn.
And we can control exactly how that works
using this threshold option.
So here's the deal: if I was to
crank the threshold value all the way down to one,
I'm saying the line has to be darker
than a luminance level of one in order to be traced,
which means that we're not tracing anything
inside this image whatsoever.
Because zero is black, one is extremely dark.
If I were to crank this value all the way up
to its maximum of 255, which is white,
then I'm saying trace everything because after all,
everything is at least white inside of this image.
So those are your two extremes,
what you wanna do is experiment with this value.
By default, it's set to 128, if I can get it there,
which is medium grays, so we're just basically
tracing the darkest half of the image
and leaving the whitest half untraced.
If you find that you're tracing too much of the image,
so you're tracing too many lines
and you're tracing a bunch of noise, for example,
in the image, then you wanna reduce this value.
In my case, we've gotta take it up to about 80,
now it's 81, in order to trace much of anything,
as we're seeing right here.
But I obviously wanna trace
much more of the image than this,
so I'm gonna crank this value up.
And I ultimately came up with a value,
if I can hit it here, of 180.
And notice, every single time I modify this value,
I'm previewing the effect inside the document window
because I have the preview checkbox turned on.
If you don't want that to happen,
if you wanna be able to modify a value
without these constant previews,
which do slow things down,
then just go ahead and turn the preview checkbox off
and then modify the value as desired
and turn on the preview checkbox
in order to see the results update on-screen.
Now in my mind that's a little too much,
so as I was saying I'm gonna go ahead
and take my value down to 180,
at which point I get a pretty good mix
because what ends up happening
if I go too high with this value
is the text starts filling in,
and so does my signature down here
in the bottom right hand corner.
And so, as I say, you can experiment
with this value as much as you'd like,
and you can get a lot of good results out of it.
So just so we can see how far we've come here,
I'll go ahead and reduce that value
back to 128, at which point I will of course
have to wait for the modifications to occur on-screen.
You can see that we were missing a lot of lines
at the beginning of this movie,
but if I now press Control-Z, or Command-Z on the Mac,
to undo that change, which by the way
forces Illustrator to perform a recalculation,
you can now see that we've got some
really good detail out of this autotraced effect.
And that's how you control the amount of detail
that Illustrator traces using the threshold value
in the Image Trace panel.