Someone demoed something similar to what I need in "Attempt 3" at http://sound-of-silence.com/?article=20170205. That code was written for macOS, however, and used NSBitmapImageRep (and in a way that it didn't elaborate on) to exclude blank images/textures.
My iOS app converts and processes text information as follows: UITextViews to UIImages to SKTextures to thousands of very small SK Textures [using SKTexture(rect:in:)] to thousands of SKSpriteNodes, which are then animated.
The problem with my approach is that most of the thousands of SKTextures/SKSpriteNodes are blank, with alpha = 0. So the app effectively creates a lot of nothing (in addition to the visible stuff) and moves it around unnecessarily. That seems very wasteful.
What I'd like to know is how I could get image info so as to avoid creating, or at least not further process, blank SKTextures. Any insights or suggestions would be appreciated.