Antialiasing 2 (Back to the Basics Series)
Application: Photoshop
One place where this knowledge might help you think is in Photoshop, especially if you're designing for compositing software or DVD production. Say you're doing a glass bug for your video: did you notice the anti-alias checkbox when you used the Magic Wand tool? That checkbox means that the computer will actually select fractions of pixels on the edge of the selection it shows - "blurring" the selection boundary in the same way that it did to the red channel in the example reproduced below.

One place where this knowledge might help you think is in Photoshop, especially if you're designing for compositing software or DVD production. Say you're doing a glass bug for your video: did you notice the anti-alias checkbox when you used the Magic Wand tool? That checkbox means that the computer will actually select fractions of pixels on the edge of the selection it shows - "blurring" the selection boundary in the same way that it did to the red channel in the example reproduced below.

More often than not, you're going to want to make sure that it's checked, because it will make your selection more visually attractive. But if you look back at the Transparency and Alpha Back to Basics series, you'll recall that some image formats - like GIFs and DVD buttons - only support basic, on/off transparency. If you're creating an image with transparency for applications like these, it might be smart to turn off the antialiasing when you're making selections, because that's how it will look to your viewer at the end of the day.
Here's an exercise for the reader: below, there are two screenshots from Photoshop using the Marquee (Selection) Tool. Why is the anti-alias checkbox disabled in one case, but not in the other? For the case that has the anti-alias checkbox, what would happen differently if the checkbox were unchecked?

Here's an exercise for the reader: below, there are two screenshots from Photoshop using the Marquee (Selection) Tool. Why is the anti-alias checkbox disabled in one case, but not in the other? For the case that has the anti-alias checkbox, what would happen differently if the checkbox were unchecked?

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