Visual Effects - iOS Core Animation - page 61

self .imageView. layer . mask = maskLayer;
}
@end
Figure 4.13 Our UIImageView , after the mask layer has been applied
The really cool feature of CALayer masking is that you are not limited to using static
images for your masks. Anything that can be composed out of layers can be used as the
mask property, which means that your masks can be created dynamically using code, and
even animated in real time.
Scaling Filters
The final topic we cover in this chapter is the effect of the minificationFilter and
magnificationFilter properties. Generally on iOS, when you display images, you
should try to display them at the correct size (that is, with a 1:1 correlation between the
pixels in the image and the pixels onscreen). The reasons for this are as follows:
▪ It provides the best possible quality, because the pixels aren't stretched or resampled.
▪ It makes the best use of RAM, because you aren't storing more pixels than needed.
▪ It yields the best performance, because the GPU doesn't have to work as hard.