feat: make emoji as cell content

iOSLab/InstaStyleParticle/InstaStyleParticleVC.swift

@@ -18,22 +18,35 @@ class InstaStyleParticleVC: UIViewController {
 
 extension InstaStyleParticleVC {
     private func generateParticle() {
-        let heartEmitter = CAEmitterLayer()
-        heartEmitter.emitterPosition = CGPoint(x: view.bounds.width/2, y: view.bounds.height/2)
-        heartEmitter.emitterSize = CGSize(width: 100, height: 100)
-        heartEmitter.emitterShape = .point
+        let emitterLayer = CAEmitterLayer()
+        emitterLayer.emitterPosition = CGPoint(x: view.bounds.width/2, y: view.bounds.height - 100)
+        emitterLayer.emitterSize = CGSize(width: 100, height: 100)
+        emitterLayer.emitterShape = .point
 
-        let heartCell = CAEmitterCell()
-        heartCell.contents = UIImage(named: "heart.png")?.cgImage
-        heartCell.birthRate = 5
-        heartCell.lifetime = 1.0
-        heartCell.velocity = 100
-        heartCell.emissionRange = .pi / 5
-        heartCell.emissionLongitude = .pi / -2
-        heartCell.alphaRange = 0.3
-        heartCell.alphaSpeed = -0.5
-
-        heartEmitter.emitterCells = [heartCell]
-        view.layer.addSublayer(heartEmitter)
+        let emitterCell = CAEmitterCell()
+        emitterCell.contents = {
+            let emoji = "🎉"
+            let font = UIFont.systemFont(ofSize: 20)
+            let size = emoji.size(withAttributes: [.font: font])
+            let renderer = UIGraphicsImageRenderer(size: size)
+            let image = renderer.image { context in
+                emoji.draw(at: .zero, withAttributes: [.font: font])
+            }
+            return image.cgImage
+        }()
+        emitterCell.birthRate = 20
+        emitterCell.lifetime = 1.0
+        emitterCell.velocity = 300
+        emitterCell.velocityRange = 50
+        emitterCell.emissionRange = .pi / 5
+        emitterCell.emissionLongitude = .pi / -2
+        emitterCell.alphaRange = 0.3
+        emitterCell.alphaSpeed = -0.5
+        emitterCell.scale = 0.15
+        emitterCell.scaleRange = 1
+        emitterCell.scaleSpeed = 0.5
+
+        emitterLayer.emitterCells = [emitterCell]
+        view.layer.addSublayer(emitterLayer)
     }
 }