From 5b71dfe0ca0073aca27f44e9249ba9e3379d22c9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kevin=20Varga=20Hala=CC=81sz?= <vargakevin@icloud.com>
Date: Fri, 28 Oct 2022 16:19:37 +0200
Subject: [PATCH] Improving performance of BlurHashDecode (Swift)

---
 Swift/BlurHashDecode.swift | 72 ++++++++++++++++++++++++++------------
 1 file changed, 49 insertions(+), 23 deletions(-)

diff --git a/Swift/BlurHashDecode.swift b/Swift/BlurHashDecode.swift
index 7fe3b398..6d18e613 100644
--- a/Swift/BlurHashDecode.swift
+++ b/Swift/BlurHashDecode.swift
@@ -3,65 +3,91 @@ import UIKit
 extension UIImage {
     public convenience init?(blurHash: String, size: CGSize, punch: Float = 1) {
         guard blurHash.count >= 6 else { return nil }
-
-		let sizeFlag = String(blurHash[0]).decode83()
-		let numY = (sizeFlag / 9) + 1
-		let numX = (sizeFlag % 9) + 1
-
-		let quantisedMaximumValue = String(blurHash[1]).decode83()
+        
+        let sizeFlag = String(blurHash[0]).decode83()
+        let numY = (sizeFlag / 9) + 1
+        let numX = (sizeFlag % 9) + 1
+        
+        let quantisedMaximumValue = String(blurHash[1]).decode83()
         let maximumValue = Float(quantisedMaximumValue + 1) / 166
-
+        
         guard blurHash.count == 4 + 2 * numX * numY else { return nil }
-
+        
         let colours: [(Float, Float, Float)] = (0 ..< numX * numY).map { i in
             if i == 0 {
-				let value = String(blurHash[2 ..< 6]).decode83()
+                let value = String(blurHash[2 ..< 6]).decode83()
                 return decodeDC(value)
             } else {
                 let value = String(blurHash[4 + i * 2 ..< 4 + i * 2 + 2]).decode83()
                 return decodeAC(value, maximumValue: maximumValue * punch)
             }
         }
-
+        
         let width = Int(size.width)
         let height = Int(size.height)
         let bytesPerRow = width * 3
         guard let data = CFDataCreateMutable(kCFAllocatorDefault, bytesPerRow * height) else { return nil }
         CFDataSetLength(data, bytesPerRow * height)
         guard let pixels = CFDataGetMutableBytePtr(data) else { return nil }
-
-        for y in 0 ..< height {
-            for x in 0 ..< width {
+        
+        var y = 0
+        
+        let floatWidth = Float(width)
+        
+        let floatHeight = Float(height)
+        
+        while y < height {
+            var x = 0
+            
+            let floatY : Float = Float(y)
+            
+            while x < width {
+                var j = 0
+                
                 var r: Float = 0
                 var g: Float = 0
                 var b: Float = 0
-
-                for j in 0 ..< numY {
-                    for i in 0 ..< numX {
-                        let basis = cos(Float.pi * Float(x) * Float(i) / Float(width)) * cos(Float.pi * Float(y) * Float(j) / Float(height))
+                
+                let floatX : Float = Float(x)
+                
+                while j < numY {
+                    var i = 0
+                    
+                    let floatJ : Float = Float(j)
+                    
+                    while i < numX {
+                        let basis = cos(Float.pi * floatX * Float(i) / floatWidth) * cos(Float.pi * floatY * floatJ / floatHeight)
                         let colour = colours[i + j * numX]
                         r += colour.0 * basis
                         g += colour.1 * basis
                         b += colour.2 * basis
+                        
+                        i += 1
                     }
+                    
+                    j += 1
                 }
-
+                
                 let intR = UInt8(linearTosRGB(r))
                 let intG = UInt8(linearTosRGB(g))
                 let intB = UInt8(linearTosRGB(b))
-
+                
                 pixels[3 * x + 0 + y * bytesPerRow] = intR
                 pixels[3 * x + 1 + y * bytesPerRow] = intG
                 pixels[3 * x + 2 + y * bytesPerRow] = intB
+                
+                x += 1
             }
+            
+            y += 1
         }
-
+        
         let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.none.rawValue)
-
+        
         guard let provider = CGDataProvider(data: data) else { return nil }
         guard let cgImage = CGImage(width: width, height: height, bitsPerComponent: 8, bitsPerPixel: 24, bytesPerRow: bytesPerRow,
-        space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: bitmapInfo, provider: provider, decode: nil, shouldInterpolate: true, intent: .defaultIntent) else { return nil }
-
+                                    space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: bitmapInfo, provider: provider, decode: nil, shouldInterpolate: true, intent: .defaultIntent) else { return nil }
+        
         self.init(cgImage: cgImage)
     }
 }