October 10th lecture

playgrounds/extensions/UIImage+crop.playground/Contents.swift

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+import UIKit
+
+var str = "Hello, playground"
+
+extension UIImage {
+    // add a crop function to UIImage
+    func crop(to: CGRect) -> UIImage? {
+        switch (self.cgImage, self.ciImage) {
+        // check if cgImage is some, ciImage is nil and unwrap self.cgImage, storing it in cgImage
+        case (.some(let cgImage), nil):
+            let image = cgImage.cropping(to: to)
+            return image.map { UIImage(cgImage: $0) }
+        case (nil, .some(let ciImage)):
+            return UIImage(ciImage: ciImage.cropped(to: to))
+        default:
+            print("I don't know why cgImage and ciImage are equal")
+            return nil
+        }
+    }
+}
+
+var image: UIImage = UIImage() // assume set elsewhere
+let croppedImage = image.crop(to: CGRect(x: 0.0, y: 0.0, width: 25.0, height: 25.0))

playgrounds/extensions/UIImage+crop.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' executeOnSourceChanges='false'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>

playgrounds/extensions/UIImage+crop.playground/playground.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>