Normalize color spaces before comparing images

Use the sRGB converted snapshot when doing the perceptual comparison

This reduces the chances of failures when comparing snapshots in different color spaces

Sources/SnapshotTesting/Snapshotting/NSImage.swift

@@ -94,8 +94,8 @@ private func compare(_ old: NSImage, _ new: NSImage, precision: Float, perceptua
   }
   if perceptualPrecision < 1, #available(macOS 10.13, *) {
     return perceptuallyCompare(
-      CIImage(cgImage: oldCgImage),
-      CIImage(cgImage: newCgImage),
+      CIImage(cgImage: oldContext.makeImage() ?? oldCgImage),
+      CIImage(cgImage: newerContext.makeImage() ?? newerCgImage),
       pixelPrecision: precision,
       perceptualPrecision: perceptualPrecision
     )
@@ -119,7 +119,7 @@ private func compare(_ old: NSImage, _ new: NSImage, precision: Float, perceptua
 
 private func context(for cgImage: CGImage) -> CGContext? {
   guard
-    let space = cgImage.colorSpace,
+    let space = CGColorSpace(name: CGColorSpace.sRGB) ?? cgImage.colorSpace,
     let context = CGContext(
       data: nil,
       width: cgImage.width,

Sources/SnapshotTesting/Snapshotting/UIImage.swift

@@ -94,7 +94,10 @@ private func compare(_ old: UIImage, _ new: UIImage, precision: Float, perceptua
   let pixelCount = oldCgImage.width * oldCgImage.height
   let byteCount = imageContextBytesPerPixel * pixelCount
   var oldBytes = [UInt8](repeating: 0, count: byteCount)
-  guard let oldData = context(for: oldCgImage, data: &oldBytes)?.data else {
+  guard
+    let oldContext = context(for: oldCgImage, data: &oldBytes),
+    let oldData = oldContext.data
+  else {
     return "Reference image's data could not be loaded."
   }
   if let newContext = context(for: newCgImage), let newData = newContext.data {
@@ -115,8 +118,8 @@ private func compare(_ old: UIImage, _ new: UIImage, precision: Float, perceptua
   }
   if perceptualPrecision < 1, #available(iOS 11.0, tvOS 11.0, *) {
     return perceptuallyCompare(
-      CIImage(cgImage: oldCgImage),
-      CIImage(cgImage: newCgImage),
+      CIImage(cgImage: oldContext.makeImage() ?? oldCgImage),
+      CIImage(cgImage: newerContext.makeImage() ?? newerCgImage),
       pixelPrecision: precision,
       perceptualPrecision: perceptualPrecision
     )

Tests/SnapshotTestingTests/SnapshotTestingTests.swift

@@ -20,6 +20,10 @@ import XCTest
 @testable import SnapshotTesting
 
 final class SnapshotTestingTests: XCTestCase {
+  private let fixturesURL = URL(fileURLWithPath: #file, isDirectory: false)
+    .deletingLastPathComponent()
+    .appendingPathComponent("__Fixtures__", isDirectory: true)
+
   override func setUp() {
     super.setUp()
     diffTool = "ksdiff"
@@ -291,19 +295,40 @@ final class SnapshotTestingTests: XCTestCase {
 
   func testImagePrecision() throws {
     #if os(iOS) || os(tvOS) || os(macOS)
-    let imageURL = URL(fileURLWithPath: String(#file), isDirectory: false)
-            .deletingLastPathComponent()
-            .appendingPathComponent("__Fixtures__/testImagePrecision.reference.png")
+    let imageURL = fixturesURL
+            .appendingPathComponent(sanitizePathComponent(#function), isDirectory: false)
+            .appendingPathExtension("reference.png")
     #if os(iOS) || os(tvOS)
     let image = try XCTUnwrap(UIImage(contentsOfFile: imageURL.path))
     #elseif os(macOS)
     let image = try XCTUnwrap(NSImage(byReferencing: imageURL))
     #endif
 
     assertSnapshot(matching: image, as: .image(precision: 0.995), named: "exact")
-    if #available(iOS 11.0, tvOS 11.0, macOS 10.13, *) {
-      assertSnapshot(matching: image, as: .image(perceptualPrecision: 0.98), named: "perceptual")
-    }
+    assertSnapshot(matching: image, as: .image(perceptualPrecision: 0.98), named: "perceptual")
+    #endif
+  }
+
+  func testImageColorSpaceConversion() throws {
+    #if os(iOS) || os(tvOS) || os(macOS)
+    let fileName = URL(fileURLWithPath: #file, isDirectory: false).deletingPathExtension().lastPathComponent
+    let baseImageURL = URL(fileURLWithPath: #file, isDirectory: false)
+      .deletingLastPathComponent()
+      .appendingPathComponent("__Snapshots__", isDirectory: true)
+      .appendingPathComponent(fileName, isDirectory: true)
+      .appendingPathComponent(sanitizePathComponent(#function), isDirectory: false)
+    let p3ImageURL = baseImageURL.appendingPathExtension("p3.png")
+    let sRGBImageURL = baseImageURL.appendingPathExtension("srgb.png")
+    #if os(iOS) || os(tvOS)
+    let p3Image = try XCTUnwrap(UIImage(contentsOfFile: p3ImageURL.path))
+    let sRGBImage = try XCTUnwrap(UIImage(contentsOfFile: sRGBImageURL.path))
+    #elseif os(macOS)
+    let p3Image = try XCTUnwrap(NSImage(byReferencing: p3ImageURL))
+    let sRGBImage = try XCTUnwrap(NSImage(byReferencing: sRGBImageURL))
+    #endif
+
+    assertSnapshot(matching: p3Image, as: .image(perceptualPrecision: 0.99), named: "srgb")
+    assertSnapshot(matching: sRGBImage, as: .image(perceptualPrecision: 0.99), named: "p3")
     #endif
   }
 
@@ -319,9 +344,7 @@ final class SnapshotTestingTests: XCTestCase {
 //      sphereNode.position = SCNVector3Zero
 //      scene.rootNode.addChildNode(sphereNode)
 //
-//      sphereGeometry.firstMaterial?.diffuse.contents = URL(fileURLWithPath: String(#file), isDirectory: false)
-//        .deletingLastPathComponent()
-//        .appendingPathComponent("__Fixtures__/earth.png")
+//      sphereGeometry.firstMaterial?.diffuse.contents = fixturesURL.appendingPathComponent("earth.png", isDirectory: false)
 //
 //      let cameraNode = SCNNode()
 //      cameraNode.camera = SCNCamera()
@@ -1029,9 +1052,7 @@ final class SnapshotTestingTests: XCTestCase {
 
   func testWebView() throws {
     #if os(iOS) || os(macOS)
-    let fixtureUrl = URL(fileURLWithPath: String(#file), isDirectory: false)
-      .deletingLastPathComponent()
-      .appendingPathComponent("__Fixtures__/pointfree.html")
+    let fixtureUrl = fixturesURL.appendingPathComponent("pointfree.html", isDirectory: false)
     let html = try String(contentsOf: fixtureUrl)
     let webView = WKWebView()
     webView.loadHTMLString(html, baseURL: nil)
@@ -1080,9 +1101,7 @@ final class SnapshotTestingTests: XCTestCase {
     let label = UILabel()
     label.text = "Hello, Blob!"
 
-    let fixtureUrl = URL(fileURLWithPath: String(#file), isDirectory: false)
-      .deletingLastPathComponent()
-      .appendingPathComponent("__Fixtures__/pointfree.html")
+    let fixtureUrl = fixturesURL.appendingPathComponent("pointfree.html", isDirectory: false)
     let html = try String(contentsOf: fixtureUrl)
     let webView = WKWebView()
     webView.loadHTMLString(html, baseURL: nil)
@@ -1112,9 +1131,7 @@ final class SnapshotTestingTests: XCTestCase {
     let webView = WKWebView()
     webView.navigationDelegate = manipulatingWKWebViewNavigationDelegate
 
-    let fixtureUrl = URL(fileURLWithPath: String(#file), isDirectory: false)
-      .deletingLastPathComponent()
-      .appendingPathComponent("__Fixtures__/pointfree.html")
+    let fixtureUrl = fixturesURL.appendingPathComponent("pointfree.html", isDirectory: false)
     let html = try String(contentsOf: fixtureUrl)
     webView.loadHTMLString(html, baseURL: nil)
     if !ProcessInfo.processInfo.environment.keys.contains("GITHUB_WORKFLOW") {
@@ -1159,9 +1176,7 @@ final class SnapshotTestingTests: XCTestCase {
     let webView = WKWebView()
     webView.navigationDelegate = cancellingWKWebViewNavigationDelegate
 
-    let fixtureUrl = URL(fileURLWithPath: String(#file), isDirectory: false)
-      .deletingLastPathComponent()
-      .appendingPathComponent("__Fixtures__/pointfree.html")
+    let fixtureUrl = fixturesURL.appendingPathComponent("pointfree.html", isDirectory: false)
     let html = try String(contentsOf: fixtureUrl)
     webView.loadHTMLString(html, baseURL: nil)
     if !ProcessInfo.processInfo.environment.keys.contains("GITHUB_WORKFLOW") {