55 lines
1.7 KiB
Swift
Executable File
55 lines
1.7 KiB
Swift
Executable File
import UIKit
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import ImageIO
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import MobileCoreServices
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internal typealias GIFProperties = [String : Double]
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private let defaultDuration: Double = 0
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func CGImageSourceGIFFrameDuration(imageSource: CGImageSource, index: Int) -> NSTimeInterval {
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if !imageSource.isAnimatedGIF { return 0.0 }
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let duration = imageSource.GIFPropertiesAtIndex(UInt(index))
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>>- durationFromGIFProperties
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>>- capDuration
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return duration ?? defaultDuration
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}
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private func capDuration(duration: Double) -> Double? {
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if duration < 0 { return .None }
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let threshold = 0.02 - Double(FLT_EPSILON)
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let cappedDuration = duration < threshold ? 0.1 : duration
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return cappedDuration
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}
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private func durationFromGIFProperties(properties: GIFProperties) -> Double? {
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let unclampedDelayTime = properties[String(kCGImagePropertyGIFUnclampedDelayTime)]
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let delayTime = properties[String(kCGImagePropertyGIFDelayTime)]
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return duration <^> unclampedDelayTime <*> delayTime
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}
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private func duration(unclampedDelayTime: Double)(delayTime: Double) -> Double {
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let delayArray = [unclampedDelayTime, delayTime]
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return delayArray.filter(isPositive).first ?? defaultDuration
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}
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private func isPositive(value: Double) -> Bool {
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return value >= 0
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}
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extension CGImageSourceRef {
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var isAnimatedGIF: Bool {
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let isTypeGIF = UTTypeConformsTo(CGImageSourceGetType(self), kUTTypeGIF)
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let imageCount = CGImageSourceGetCount(self)
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return isTypeGIF != 0 && imageCount > 1
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}
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func GIFPropertiesAtIndex(index: UInt) -> GIFProperties? {
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if !isAnimatedGIF { return .None }
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let imageProperties = CGImageSourceCopyPropertiesAtIndex(self, index, nil) as Dictionary
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return imageProperties[String(kCGImagePropertyGIFDictionary)] as? GIFProperties
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}
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}
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