Add support for renderscale (#7)

* Add support for renderscale

* Fix

Sources/SnapshotTestCase/Extensions/UIImageExtensions+Resize.swift

@@ -0,0 +1,19 @@
+import UIKit
+
+extension UIImage {
+    func resized(toScale scale: CGFloat) -> UIImage? {
+        guard scale > 0, scale != 1 else {
+            return self
+        }
+        return resized(toWidth: scale * size.width)
+    }
+
+    func resized(toWidth width: CGFloat, isOpaque: Bool = true) -> UIImage? {
+        let canvas = CGSize(width: width, height: CGFloat(ceil(width / size.width * size.height)))
+        let format = imageRendererFormat
+        format.opaque = isOpaque
+        return UIGraphicsImageRenderer(size: canvas, format: format).image { _ in
+            draw(in: CGRect(origin: .zero, size: canvas))
+        }
+    }
+}

Sources/SnapshotTestCase/Models/LaunchEnvironment.swift

@@ -6,6 +6,7 @@ enum LaunchEnvironment {
         static let failurePath: String = "snapshotFailures"
         static let tolerance: String = "snapshotTolerance"
         static let renderOffsetY: String = "snapshotRenderOffsetY"
+        static let renderScale: String = "snapshotRenderScale"
         static let recordMode: String = "-RecordingSnapshot"
     }
 
@@ -34,4 +35,11 @@ enum LaunchEnvironment {
         }
         return Double(renderOffsetY) ?? 0
     }
+
+    static var renderScale: CGFloat {
+        guard let renderScale = ProcessInfo.processInfo.environment[Key.renderScale] else {
+            return 1
+        }
+        return Double(renderScale) ?? 1
+    }
 }

Sources/SnapshotTestCase/Snapshot.swift

@@ -3,6 +3,7 @@ import UIKit
 
 public class Snapshot {
     static var renderOffsetY: CGFloat = LaunchEnvironment.renderOffsetY
+    static var renderScale: CGFloat = LaunchEnvironment.renderScale
 
     enum Constants {
         static let imageExt: String = "png"
@@ -189,9 +190,11 @@ private extension Snapshot.TestCase {
         let window = UIWindow(frame: CGRect(origin: .zero, size: size))
         window.rootViewController = viewController
         window.makeKeyAndVisible()
-        let snapshot = try await renderSnapshot(view: view, in: size)
-        window.removeFromSuperview()
-        return try await crop(snapshot, to: size)
+        defer { window.removeFromSuperview() }
+        var snapshot = try await renderSnapshot(view: view, in: size)        
+        snapshot = try await crop(snapshot, to: size)
+        snapshot = try await resize(snapshot, to: Snapshot.renderScale)
+        return snapshot
     }
 
     @MainActor
@@ -223,6 +226,14 @@ private extension Snapshot.TestCase {
         return UIImage(cgImage: cgImage)
     }
 
+    @MainActor
+    private func resize(_ image: UIImage, to scale: CGFloat) async throws -> UIImage {
+        guard let image = image.resized(toScale: scale) else {
+            throw SnapshotError.resizeSnapshot
+        }
+        return image
+    }
+
     @MainActor
     private func create(
         with config: SnapshotConfig.Config,

Sources/SnapshotTestCase/SnapshotError.swift

@@ -15,6 +15,7 @@ public enum SnapshotError: Error {
     case comparison(Error)
     case referenceImageNotEqual(Double)
     case cropSnapshot
+    case resizeSnapshot
     case timeout(String)
     case unknown(Error)
 }