71 lines
2.7 KiB
Swift
Executable File
71 lines
2.7 KiB
Swift
Executable File
import ImageIO
|
|
import MobileCoreServices
|
|
import UIKit
|
|
|
|
typealias GIFProperties = [String: Double]
|
|
let defaultDuration: Double = 0
|
|
|
|
/// Retruns the duration of a frame at a specific index using an image source (an `CGImageSource` instance).
|
|
///
|
|
/// - returns: A frame duration.
|
|
func CGImageFrameDuration(with imageSource: CGImageSource, atIndex index: Int) -> TimeInterval {
|
|
if !imageSource.isAnimatedGIF { return 0.0 }
|
|
|
|
guard let GIFProperties = imageSource.properties(at: index),
|
|
let duration = frameDuration(with: GIFProperties),
|
|
let cappedDuration = capDuration(with: duration)
|
|
else { return defaultDuration }
|
|
|
|
return cappedDuration
|
|
}
|
|
|
|
/// Ensures that a duration is never smaller than a threshold value.
|
|
///
|
|
/// - returns: A capped frame duration.
|
|
func capDuration(with duration: Double) -> Double? {
|
|
if duration < 0 { return .none }
|
|
let threshold = 0.02 - Double(FLT_EPSILON)
|
|
let cappedDuration = duration < threshold ? 0.1 : duration
|
|
return cappedDuration
|
|
}
|
|
|
|
/// Returns a frame duration from a `GIFProperties` dictionary.
|
|
///
|
|
/// - returns: A frame duration.
|
|
func frameDuration(with properties: GIFProperties) -> Double? {
|
|
guard let unclampedDelayTime = properties[String(kCGImagePropertyGIFUnclampedDelayTime)],
|
|
let delayTime = properties[String(kCGImagePropertyGIFDelayTime)]
|
|
else { return .none }
|
|
|
|
return duration(withUnclampedTime: unclampedDelayTime, andClampedTime: delayTime)
|
|
}
|
|
|
|
/// Calculates frame duration based on both clamped and unclamped times.
|
|
///
|
|
/// - returns: A frame duration.
|
|
func duration(withUnclampedTime unclampedDelayTime: Double, andClampedTime delayTime: Double) -> Double {
|
|
let delayArray = [unclampedDelayTime, delayTime]
|
|
return delayArray.filter({ $0 >= 0 }).first ?? defaultDuration
|
|
}
|
|
|
|
/// An extension of `CGImageSourceRef` that add GIF introspection and easier property retrieval.
|
|
extension CGImageSource {
|
|
/// Returns whether the image source contains an animated GIF.
|
|
///
|
|
/// - returns: A boolean value that is `true` if the image source contains animated GIF data.
|
|
var isAnimatedGIF: Bool {
|
|
let isTypeGIF = UTTypeConformsTo(CGImageSourceGetType(self) ?? "" as CFString, kUTTypeGIF)
|
|
let imageCount = CGImageSourceGetCount(self)
|
|
return isTypeGIF != false && imageCount > 1
|
|
}
|
|
|
|
/// Returns the GIF properties at a specific index.
|
|
///
|
|
/// - parameter index: The index of the GIF properties to retrieve.
|
|
/// - returns: A dictionary containing the GIF properties at the passed in index.
|
|
func properties(at index: Int) -> GIFProperties? {
|
|
guard let imageProperties = CGImageSourceCopyPropertiesAtIndex(self, index, nil) as? [String: AnyObject] else { return nil }
|
|
return imageProperties[String(kCGImagePropertyGIFDictionary)] as? GIFProperties
|
|
}
|
|
}
|