Merge pull request #15 from indragiek/color-diff

Add CIE76 and CIE94 algorithms

DominantColor.xcodeproj/project.pbxproj

@@ -40,6 +40,8 @@
 		723DE5C51A4939A200C357E3 /* KMeans.swift in Sources */ = {isa = PBXBuildFile; fileRef = 723DE51A1A49348D00C357E3 /* KMeans.swift */; };
 		723DE5C61A4939A300C357E3 /* ColorSpaceConversion.m in Sources */ = {isa = PBXBuildFile; fileRef = 723DE5161A49348D00C357E3 /* ColorSpaceConversion.m */; };
 		723DE5C71A4939A500C357E3 /* INVector3.m in Sources */ = {isa = PBXBuildFile; fileRef = 723DE5191A49348D00C357E3 /* INVector3.m */; };
+		72431C0F1A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 72431C0E1A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift */; };
+		72431C101A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift in Sources */ = {isa = PBXBuildFile; fileRef = 72431C0E1A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -111,6 +113,7 @@
 		723DE5741A49388400C357E3 /* ExampleiOS-Bridging-Header.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = "ExampleiOS-Bridging-Header.h"; path = "DominantColor/iOS/ExampleiOS-Bridging-Header.h"; sourceTree = SOURCE_ROOT; };
 		723DE59F1A4938DD00C357E3 /* DominantColor.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = DominantColor.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		723DE5BE1A49394D00C357E3 /* GLKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = GLKit.framework; path = Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.1.sdk/System/Library/Frameworks/GLKit.framework; sourceTree = DEVELOPER_DIR; };
+		72431C0E1A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = INVector3SwiftExtensions.swift; sourceTree = "<group>"; };
 		72D797B81A43F44D00D32E7C /* ExampleMac.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = ExampleMac.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		72D797DE1A43F89000D32E7C /* GLKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = GLKit.framework; path = System/Library/Frameworks/GLKit.framework; sourceTree = SDKROOT; };
 		898845D21A490CE000003EF2 /* ExampleiOS.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = ExampleiOS.app; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -162,6 +165,7 @@
 				723DE5171A49348D00C357E3 /* DominantColors.swift */,
 				723DE5181A49348D00C357E3 /* INVector3.h */,
 				723DE5191A49348D00C357E3 /* INVector3.m */,
+				72431C0E1A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift */,
 				723DE51A1A49348D00C357E3 /* KMeans.swift */,
 				723DE5381A49353C00C357E3 /* Supporting Files */,
 				2F3D09851A4C212A001ED0BF /* Memoization.swift */,
@@ -443,6 +447,7 @@
 			files = (
 				2F3D09861A4C212A001ED0BF /* Memoization.swift in Sources */,
 				723DE55C1A49360F00C357E3 /* ColorDifference.swift in Sources */,
+				72431C0F1A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift in Sources */,
 				723DE55D1A49361100C357E3 /* DominantColors.swift in Sources */,
 				723DE55E1A49361200C357E3 /* KMeans.swift in Sources */,
 				723DE5601A49361900C357E3 /* ColorSpaceConversion.m in Sources */,
@@ -456,6 +461,7 @@
 			files = (
 				2F3D09871A4C212A001ED0BF /* Memoization.swift in Sources */,
 				723DE5C31A49399E00C357E3 /* ColorDifference.swift in Sources */,
+				72431C101A4BCF3B00470BD7 /* INVector3SwiftExtensions.swift in Sources */,
 				723DE5C41A4939A000C357E3 /* DominantColors.swift in Sources */,
 				723DE5C51A4939A200C357E3 /* KMeans.swift in Sources */,
 				723DE5C61A4939A300C357E3 /* ColorSpaceConversion.m in Sources */,

DominantColor/Mac/AppDelegate.swift

@@ -35,7 +35,7 @@ class AppDelegate: NSObject, NSApplicationDelegate, DragAndDropImageViewDelegate
             let CGImage = image.CGImageForProposedRect(nil, context: nil, hints: nil)!.takeUnretainedValue()
             for n in nValues {
                 let ns = dispatch_benchmark(5) {
-                    dominantColorsInImage(CGImage, n, 98251)
+                    dominantColorsInImage(CGImage, maxSampledPixels: n)
                     return
                 }
                 println("n = \(n) averaged \(ns/1000000) ms")
@@ -49,7 +49,7 @@ class AppDelegate: NSObject, NSApplicationDelegate, DragAndDropImageViewDelegate
 
             self.image = image
             let CGImage = image.CGImageForProposedRect(nil, context: nil, hints: nil)!.takeUnretainedValue()
-            let colors = dominantColorsInImage(CGImage, 1000, 98251)
+            let colors = dominantColorsInImage(CGImage)
             let boxes = [box1, box2, box3, box4, box5, box6]
 
             for box in boxes {

DominantColor/Shared/ColorDifference.swift

@@ -6,29 +6,61 @@
 //  Copyright (c) 2014 Indragie Karunaratne. All rights reserved.
 //
 
-private func degToRad(deg: Float) -> Float {
-    return deg * Float(M_PI) / 180
+import GLKit.GLKMath
+
+// These functions return the squared color difference because for distance 
+// calculations it doesn't matter and saves an unnecessary computation.
+
+// From http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE76.html
+func CIE76SquaredColorDifference(lab1: INVector3, lab2: INVector3) -> Float {
+    let (L1, a1, b1) = lab1.unpack()
+    let (L2, a2, b2) = lab2.unpack()
+
+    return pow(L2 - L1, 2) + pow(a2 - a1, 2) + pow(b2 - b1, 2)
 }
 
-private func radToDeg(rad: Float) -> Float {
-    return rad * 180 / Float(M_PI)
+private func C(a: Float, b: Float) -> Float {
+    return sqrt(pow(a, 2) + pow(b, 2))
+}
+
+// From http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE94.html
+func CIE94SquaredColorDifference(
+        kL: Float = 1,
+        kC: Float = 1,
+        kH: Float = 1,
+        K1: Float = 0.045,
+        K2: Float = 0.015
+    )(colors: (INVector3, INVector3)) -> Float {
+
+    let (L1, a1, b1) = colors.0.unpack()
+    let (L2, a2, b2) = colors.1.unpack()
+    let ΔL = L1 - L2
+
+    let (C1, C2) = (C(a1, b1), C(a2, b2))
+    let ΔC = C1 - C2
+
+    let ΔH = sqrt(pow(a1 - a2, 2) + pow(b1 - b2, 2) - pow(ΔC, 2))
+
+    let Sl: Float = 1
+    let Sc = 1 + K1 * C1
+    let Sh = 1 + K2 * C1
+
+    return pow(ΔL / (kL * Sl), 2) + pow(ΔC / (kC * Sc), 2) + pow(ΔH / (kH * Sh), 2)
 }
 
 // From http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE2000.html
-//
-// NOTE: This returns the *squared* color difference to save a sqrt() call because
-// we don't care about the absolute metric. To get the actual value of the CIE 2000
-// delta E, the output from this function must be square rooted.
-public func CIE2000SquaredColorDifference(lab1: INVector3, lab2: INVector3, kL: Float = 1, kC: Float = 1, kH: Float = 1) -> Float {
-    let (L1, a1, b1) = (lab1.x, lab1.y, lab1.z)
-    let (L2, a2, b2) = (lab2.x, lab2.y, lab2.z)
+func CIE2000SquaredColorDifference(
+        kL: Float = 1,
+        kC: Float = 1,
+        kH: Float = 1
+    )(colors: (INVector3, INVector3)) -> Float {
+
+    let (L1, a1, b1) = colors.0.unpack()
+    let (L2, a2, b2) = colors.1.unpack()
 
     let ΔLp = L2 - L1
     let Lbp = (L1 + L2) / 2
 
-    let C: (Float, Float) -> Float = { a, b in
-        return sqrt(pow(a, 2) + pow(b, 2))
-    }
     let (C1, C2) = (C(a1, b1), C(a2, b2))
     let Cb = (C1 + C2) / 2
 
@@ -44,7 +76,7 @@ public func CIE2000SquaredColorDifference(lab1: INVector3, lab2: INVector3, kL:
 
     let hp: (Float, Float) -> Float = { ap, b in
         if ap == 0 && b == 0 { return 0 }
-        let θ = radToDeg(atan2(b, ap))
+        let θ = GLKMathRadiansToDegrees(atan2(b, ap))
         return fmod(θ < 0 ? (θ + 360) : θ, 360)
     }
     let (h1p, h2p) = (hp(a1p, b1), hp(a2p, b2))
@@ -61,7 +93,7 @@ public func CIE2000SquaredColorDifference(lab1: INVector3, lab2: INVector3, kL:
         }
     }()
 
-    let ΔHp = 2 * sqrt(C1p * C2p) * sin(degToRad(Δhp / 2))
+    let ΔHp = 2 * sqrt(C1p * C2p) * sin(GLKMathDegreesToRadians(Δhp / 2))
     let Hbp: Float = {
         if (C1p == 0 || C2p == 0) {
             return h1p + h2p
@@ -73,18 +105,18 @@ public func CIE2000SquaredColorDifference(lab1: INVector3, lab2: INVector3, kL:
     }()
 
     let T = 1
-        - 0.17 * cos(degToRad(Hbp - 30))
-        + 0.24 * cos(degToRad(2 * Hbp))
-        + 0.32 * cos(degToRad(3 * Hbp + 6))
-        - 0.20 * cos(degToRad(4 * Hbp - 63))
+        - 0.17 * cos(GLKMathDegreesToRadians(Hbp - 30))
+        + 0.24 * cos(GLKMathDegreesToRadians(2 * Hbp))
+        + 0.32 * cos(GLKMathDegreesToRadians(3 * Hbp + 6))
+        - 0.20 * cos(GLKMathDegreesToRadians(4 * Hbp - 63))
 
     let Sl = 1 + (0.015 * pow(Lbp - 50, 2)) / sqrt(20 + pow(Lbp - 50, 2))
     let Sc = 1 + 0.045 * Cbp
     let Sh = 1 + 0.015 * Cbp * T
 
     let Δθ = 30 * exp(-pow((Hbp - 275) / 25, 2))
     let Rc = 2 * sqrt(pow(Cbp, 7) / (pow(Cbp, 7) + pow(25, 7)))
-    let Rt = -Rc * sin(degToRad(2 * Δθ))
+    let Rt = -Rc * sin(GLKMathDegreesToRadians(2 * Δθ))
 
     let Lterm = ΔLp / (kL * Sl)
     let Cterm = ΔCp / (kC * Sc)

DominantColor/Shared/DominantColors.swift

@@ -75,43 +75,23 @@ private extension RGBAPixel {
 
 // MARK: Clustering
 
-public func +(lhs: INVector3, rhs: INVector3) -> INVector3 {
-    return INVector3Add(lhs, rhs)
-}
-
-extension INVector3 : ClusteredType {
-    public func distance(to: INVector3) -> Float {
-        return CIE2000SquaredColorDifference(self, to)
-    }
-
-    public func divideScalar(scalar: Int) -> INVector3 {
-        return INVector3DivideScalar(self, Float(scalar))
-    }
-
-    public static var identity: INVector3 {
-        return INVector3(x: 0, y: 0, z: 0)
-    }
-}
-
-private func selectKForElements<T>(elements: [T]) -> Int {
-    // Seems like a magic number...
-    return 16
-}
+extension INVector3 : ClusteredType {}
 
 // MARK: Main
 
-// Computes the proportionally scaled dimensions such that the
-// total number of pixels does not exceed the specified limit.
-private func scaledDimensionsForPixelLimit(limit: UInt, width: UInt, height: UInt) -> (UInt, UInt) {
-    if (width * height > limit) {
-        let ratio = Float(width) / Float(height)
-        let maxWidth = sqrtf(ratio * Float(limit))
-        return (UInt(maxWidth), UInt(Float(limit) / maxWidth))
-    }
-    return (width, height)
+public enum GroupingAccuracy {
+    case Low        // CIE 76 - Euclidian distance
+    case Medium     // CIE 94 - Perceptual non-uniformity corrections
+    case High       // CIE 2000 - Additional corrections for neutral colors, lightness, chroma, and hue
 }
 
-public func dominantColorsInImage(image: CGImage, maxSampledPixels: UInt, seed: Int) -> [CGColor] {
+public func dominantColorsInImage(
+        image: CGImage,
+        maxSampledPixels: UInt = 1000,
+        accuracy: GroupingAccuracy = .Medium,
+        seed: UInt32 = 3571
+    ) -> [CGColor] {
+
     let (width, height) = (CGImageGetWidth(image), CGImageGetHeight(image))
     let (scaledWidth, scaledHeight) = scaledDimensionsForPixelLimit(maxSampledPixels, width, height)
 
@@ -132,14 +112,40 @@ public func dominantColorsInImage(image: CGImage, maxSampledPixels: UInt, seed:
             labValues.append(memoizedRGBToLAB(pixel))
         }
     }
-
     // Cluster the colors using the k-means algorithm
     let k = selectKForElements(labValues)
-    var clusters = kmeans(labValues, k, seed)
+    var clusters = kmeans(labValues, k, seed, distanceForAccuracy(accuracy))
 
     // Sort the clusters by size in descending order so that the
     // most dominant colors come first.
     clusters.sort { $0.size > $1.size }
 
     return clusters.map { RGBVectorToCGColor(IN_LABToRGB($0.centroid)) }
 }
+
+private func distanceForAccuracy(accuracy: GroupingAccuracy) -> (INVector3, INVector3) -> Float {
+    switch accuracy {
+    case .Low:
+        return CIE76SquaredColorDifference
+    case .Medium:
+        return CIE94SquaredColorDifference()
+    case .High:
+        return CIE2000SquaredColorDifference()
+    }
+}
+
+// Computes the proportionally scaled dimensions such that the
+// total number of pixels does not exceed the specified limit.
+private func scaledDimensionsForPixelLimit(limit: UInt, width: UInt, height: UInt) -> (UInt, UInt) {
+    if (width * height > limit) {
+        let ratio = Float(width) / Float(height)
+        let maxWidth = sqrtf(ratio * Float(limit))
+        return (UInt(maxWidth), UInt(Float(limit) / maxWidth))
+    }
+    return (width, height)
+}
+
+private func selectKForElements<T>(elements: [T]) -> Int {
+    // Seems like a magic number...
+    return 16
+}

DominantColor/Shared/INVector3.h

@@ -18,6 +18,3 @@ typedef struct {
 
 GLKVector3 INVector3ToGLKVector3(INVector3 vector);
 INVector3 GLKVector3ToINVector3(GLKVector3 vector);
-
-INVector3 INVector3Add(INVector3 v1, INVector3 v2);
-INVector3 INVector3DivideScalar(INVector3 vector, float scalar);

DominantColor/Shared/INVector3.m

@@ -15,11 +15,3 @@ GLKVector3 INVector3ToGLKVector3(INVector3 vector) {
 INVector3 GLKVector3ToINVector3(GLKVector3 vector) {
     return (INVector3){ vector.x, vector.y, vector.z };
 }
-
-INVector3 INVector3Add(INVector3 v1, INVector3 v2) {
-    return GLKVector3ToINVector3(GLKVector3Add(INVector3ToGLKVector3(v1), INVector3ToGLKVector3(v2)));
-}
-
-INVector3 INVector3DivideScalar(INVector3 vector, float scalar) {
-    return GLKVector3ToINVector3(GLKVector3DivideScalar(INVector3ToGLKVector3(vector), scalar));
-}

DominantColor/Shared/INVector3SwiftExtensions.swift

@@ -0,0 +1,29 @@
+//
+//  INVector3SwiftExtensions.swift
+//  DominantColor
+//
+//  Created by Indragie on 12/24/14.
+//  Copyright (c) 2014 Indragie Karunaratne. All rights reserved.
+//
+
+extension INVector3 {
+    func unpack() -> (Float, Float, Float) {
+        return (x, y, z)
+    }
+
+    static var identity: INVector3 {
+        return INVector3(x: 0, y: 0, z: 0)
+    }
+}
+
+func +(lhs: INVector3, rhs: INVector3) -> INVector3 {
+    return INVector3(x: lhs.x + rhs.x, y: lhs.y + rhs.y, z: lhs.z + rhs.z)
+}
+
+func /(lhs: INVector3, rhs: Float) -> INVector3 {
+    return INVector3(x: lhs.x / rhs, y: lhs.y / rhs, z: lhs.z / rhs)
+}
+
+func /(lhs: INVector3, rhs: Int) -> INVector3 {
+    return lhs / Float(rhs)
+}