Add frameRate option to the Gifski wrapper

In anticipation for #4

And some cleanup.

Gifski/AppDelegate.swift

@@ -1,8 +1,6 @@
 import Cocoa
 import ProgressKit
 
-private let defaults = UserDefaults.standard
-
 extension NSColor {
 	static let appTheme = NSColor(named: NSColor.Name("Theme"))!
 }
@@ -175,7 +173,7 @@ final class AppDelegate: NSObject, NSApplicationDelegate {
 
 		gifski.convertFile(
 			inputUrl,
-			outputFile: outputUrl,
+			outputUrl: outputUrl,
 			quality: defaults["outputQuality"] as! Double,
 			dimensions: choosenDimensions
 		)

Gifski/Gifski.swift

@@ -15,11 +15,16 @@ final class Gifski {
 	private(set) var progress: Double = 0
 	var onProgress: ((_ progress: Double) -> Void)?
 
+	/**
+	- parameters:
+		- frameRate: Clamped to 5...30. Uses the frame rate of `inputUrl` if not specified.
+	*/
 	func convertFile(
-		_ inputFile: URL,
-		outputFile: URL,
+		_ inputUrl: URL,
+		outputUrl: URL,
 		quality: Double = 1,
-		dimensions: CGSize? = nil
+		dimensions: CGSize? = nil,
+		frameRate: Int? = nil
 	) {
 		guard !isRunning else {
 			return
@@ -57,17 +62,17 @@ final class Gifski {
 		}, context)
 
 		DispatchQueue.global(qos: .utility).async {
-			let asset = AVURLAsset(url: inputFile, options: nil)
+			let asset = AVURLAsset(url: inputUrl, options: nil)
 			let generator = AVAssetImageGenerator(asset: asset)
 			generator.requestedTimeToleranceAfter = kCMTimeZero
 			generator.requestedTimeToleranceBefore = kCMTimeZero
 
-			let FPS = 24
-			self.frameCount = Int(asset.duration.seconds) * FPS
+			let fps = (frameRate.map { Double($0) } ?? asset.videoMetadata!.frameRate).clamped(to: 5...30)
+			self.frameCount = Int(asset.duration.seconds * fps)
 
 			var frameForTimes = [CMTime]()
 			for i in 0..<self.frameCount {
-				frameForTimes.append(CMTimeMake(Int64(i), Int32(FPS)))
+				frameForTimes.append(CMTimeMake(Int64(i), Int32(fps)))
 			}
 
 			var frameIndex = 0
@@ -85,7 +90,7 @@ final class Gifski {
 					UInt32(image.bytesPerRow),
 					UInt32(image.height),
 					buffer,
-					UInt16(100 / FPS)
+					UInt16(100 / fps)
 				)
 				precondition(result == GIFSKI_OK, String(describing: result))
 
@@ -96,7 +101,7 @@ final class Gifski {
 				}
 			}
 
-			gifski_write(g, outputFile.path)
+			gifski_write(g, outputUrl.path)
 			gifski_drop(g)
 		}
 	}

Gifski/SavePanelAccessoryViewController.swift

@@ -38,10 +38,12 @@ final class SavePanelAccessoryViewController: NSViewController {
 		}
 
 		qualitySlider.onAction = { _ in
-			UserDefaults.standard["outputQuality"] = self.qualitySlider.doubleValue
+			defaults["outputQuality"] = self.qualitySlider.doubleValue
 			estimateFileSize()
 		}
 
+		// Set initial defaults
 		dimensionsSlider.triggerAction()
+		qualitySlider.doubleValue = defaults["outputQuality"] as! Double
 	}
 }

Gifski/util.swift

@@ -2,6 +2,9 @@ import Cocoa
 import AVFoundation
 
 
+let defaults = UserDefaults.standard
+
+
 struct Meta {
 	static func openSubmitFeedbackPage() {
 		let body =
@@ -52,6 +55,53 @@ class SSView: NSView {
 }
 
 
+extension Comparable {
+	/// Note: It's not possible to implement `Range` or `PartialRangeUpTo` here as we can't know what `1.1..<1.53` would be. They only work with Stridable in our case.
+
+	/// Example: 20.5.clamped(from: 10.3, to: 15)
+	func clamped(from lowerBound: Self, to upperBound: Self) -> Self {
+		return min(max(self, lowerBound), upperBound)
+	}
+
+	/// Example: 20.5.clamped(to: 10.3...15)
+	func clamped(to range: ClosedRange<Self>) -> Self {
+		return clamped(from: range.lowerBound, to: range.upperBound)
+	}
+
+	/// Example: 20.5.clamped(to: ...10.3)
+	/// => 10.3
+	func clamped(to range: PartialRangeThrough<Self>) -> Self {
+		return min(self, range.upperBound)
+	}
+
+	/// Example: 5.5.clamped(to: 10.3...)
+	/// => 10.3
+	func clamped(to range: PartialRangeFrom<Self>) -> Self {
+		return max(self, range.lowerBound)
+	}
+}
+
+extension Strideable where Stride: SignedInteger {
+	/// Example: 20.clamped(to: 5..<10)
+	/// => 9
+	func clamped(to range: CountableRange<Self>) -> Self {
+		return clamped(from: range.lowerBound, to: range.upperBound.advanced(by: -1))
+	}
+
+	/// Example: 20.clamped(to: 5...10)
+	/// => 10
+	func clamped(to range: CountableClosedRange<Self>) -> Self {
+		return clamped(from: range.lowerBound, to: range.upperBound)
+	}
+
+	/// Example: 20.clamped(to: ..<10)
+	/// => 9
+	func clamped(to range: PartialRangeUpTo<Self>) -> Self {
+		return min(self, range.upperBound.advanced(by: -1))
+	}
+}
+
+
 extension NSViewController {
 	var appDelegate: AppDelegate {
 		return NSApp.delegate as! AppDelegate
@@ -64,7 +114,7 @@ extension AVURLAsset {
 	struct VideoMetadata {
 		let dimensions: CGSize
 		let duration: Double
-		let frameCount: Double
+		let frameRate: Double
 		let fileSize: Int
 	}
 
@@ -78,7 +128,7 @@ extension AVURLAsset {
 		return VideoMetadata(
 			dimensions: CGSize(width: fabs(dimensions.width), height: fabs(dimensions.height)),
 			duration: duration.seconds,
-			frameCount: Double(track.nominalFrameRate),
+			frameRate: Double(track.nominalFrameRate),
 			fileSize: url.fileSize
 		)
 	}