Using image pixels as an opacity mask
Video: Using image pixels as an opacity maskUntil this point we've been creating our opacity mask in a very specific way. We've been taking artwork and then we take some other kind of vector shape, be it a circle with a Gaussian blur or maybe a rectangle that has a gradient applied to it, and we've been using that vector shape as an opacity mask. However, it's important to realize again that an opacity mask is simply using the different gray levels to create the mask itself. So we're not limited to actually using vector shapes for masks. We can actually use an image as an opacity mask.
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In this installment of Illustrator Insider Training, Mordy Golding shows experienced Illustrator users how to create transparency effects and ensure reliable printing results. This course reviews the history of vector transparency and covers features such as knockout groups, opacity masks, and transparency flattening. Mordy also shows how to establish a safe workflow when placing Illustrator graphics containing transparency in PostScript, PDF, and InDesign files. A free worksheet is included with the course.
- Understanding how transparency works across the Adobe applications
- Deconstructing the Transparency panel
- Adding transparency to gradients
- Understanding how overprints and knockouts work
- Using a gradient or complex appearance as an opacity mask
- The rules of transparency flattening
- Working with complex regions
- Understanding the relationship between flattening and stacking order
- Creating and sharing flattener presets
- Saving PDF files and using the PDF/X standards
Using image pixels as an opacity mask
Until this point we've been creating our opacity mask in a very specific way. We've been taking artwork and then we take some other kind of vector shape, be it a circle with a Gaussian blur or maybe a rectangle that has a gradient applied to it, and we've been using that vector shape as an opacity mask. However, it's important to realize again that an opacity mask is simply using the different gray levels to create the mask itself. So we're not limited to actually using vector shapes for masks. We can actually use an image as an opacity mask.
In that case, the image or I should say the pixels inside of that image determine the visibility of the artwork that appears beneath it. Now in the past we've taken for example an image and put a vector shape on top of it so when we make an opacity mask the top object becomes the mask, but if we reverse the order and we put the image on top and the vectors on bottom, then it's the image that becomes the opacity mask for the vector beneath it. Let's actually apply that here in this case, because many times you know designers need to create some kind of artwork.
Let's say for example here, they are creating a T-shirt and they have some art on the T-shirt, but they want to add like that distressed look. There are parts of the art that maybe are kind of rubbed away or not visible. How do we actually do that? Many people jump through hoops to try to find ways to create this type of effect inside of Illustrator, when in reality an opacity mask does a great job at this. Let's see how that works. I'm going to open up my Layers panel here in this file that's called distress.ai, and I'll see that I now have an image here. It's called distress.psd.
I'm going to click on this little icon right here to show it inside of my file. So as you can see the image right now just sitting directly on top of the artwork. Now I'll point that that this image right now is a PSD file, but it really can be just about any image format that you would bring into Illustrator. To make life a little bit easier for myself here I've actually embedded the image but this technique also works on linked images. So the first thing I'm going to need to do is I need to actually select the artwork and also this Photoshop file. An easy way to do that is directly through the Layers panel.
So I'm going to click over here on the far right of the group to select the entire group and I'll hold down my Shift key and also click over here by the distress.psd file to select both of those elements. Next I'm going to go to the Transparency panel and from the fly-out menu choose Make Opacity Mask. So now let's take a look at just what happened. Over here the group right now has the dashed underline. The image itself now became part of that group. I no longer see that here at all inside my Layers panel. It's as if image has disappeared, but the image right now is controlling the visibility of the group.
If we look over here in my Transparency panel, this is my vector artwork. It's untouched. It's all there, but the visibility of that vector artwork is now being controlled by this image over here which serves as the opacity mask. Let's zoom in for a closer look. You can see over here that part of the image here looks like it was eaten away. The same thing over here in these different various areas. If now switch to my Direct Selection tool I can select just one of these leaves right here. Let me deselect them over here and then just select just this one leaf. It's a regular leaf that has this fill and the stroke.
However, the visibility of that is being controlled by the image which is being used as an opacity mask. The real beauty of using this to create this kind of distressed pattern is that if I zoom out just a little bit here and I actually change the color of the shirt itself. So right now I've selected just the shirt and I'll change its fill color to something else. Notice that as I changed the fill color of the shirt, that automatically now shows through to the right color, the eroded parts of my design. In fact, if I were simulating some kind of a pattern or some other kind of texture in the fabric itself, those too would show through these areas here.
So again, by using an opacity mask I'm able to control the visibility of artwork even by using the pixels inside of an image.
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