From 8fec419d55a58ac39f61663e237a9056d0b5bc37 Mon Sep 17 00:00:00 2001
From: wangjwchn <wangjwchn@yahoo.com>
Date: Sun, 24 Apr 2016 17:17:02 +0800
Subject: [PATCH] using asynchronous image decoding to reduce the main thread
 CPU usage

---
 JWAnimatedImage/JWAnimatedImageView.swift | 50 ++++++++++++++++-------
 JWAnimatedImage/JWAnimationManager.swift  |  1 +
 2 files changed, 37 insertions(+), 14 deletions(-)

diff --git a/JWAnimatedImage/JWAnimatedImageView.swift b/JWAnimatedImage/JWAnimatedImageView.swift
index d7a359f..ade710d 100644
--- a/JWAnimatedImage/JWAnimatedImageView.swift
+++ b/JWAnimatedImage/JWAnimatedImageView.swift
@@ -17,6 +17,7 @@ let _haveCacheKey = malloc(4)
 let _loopTimeKey = malloc(4)
 let _displayingKey = malloc(4)
 let _animationManagerKey = malloc(4)
+let _sameFrameCheckKey = malloc(4)
 
 public extension UIImageView{
 
@@ -42,13 +43,13 @@ public extension UIImageView{
         self.syncFactor = 0
         self.displayOrderIndex = 0
         self.cache = NSCache()
+        self.sameFrameCheck = false
         self.haveCache = false
-        self.currentImage = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,0,nil)!)
-
+        self.currentImage = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,0,[(kCGImageSourceShouldCacheImmediately as String): true])!)
         if !manager.SearchImageView(self){
             manager.AddImageView(self)
-            StartDisplay()
         }
+        StartDisplay()
     }
 
     public func StartDisplay(){
@@ -71,17 +72,11 @@ public extension UIImageView{
             self.haveCache = false
         }
     }
-
+    
     public func updateCurrentImage(){
         if(self.displaying == true){
-            if(self.haveCache==false){
-                self.currentImage = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,self.gifImage.displayOrder![self.displayOrderIndex],nil)!)
-            }else{
-                if let image = (cache.objectForKey(self.displayOrderIndex) as? UIImage){
-                    self.currentImage = image
-                }else{
-                    self.currentImage = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,self.gifImage.displayOrder![self.displayOrderIndex],nil)!)
-                }//prevent case that cache is not ready
+            if(self.sameFrameCheck == false){
+                updateFrame()
             }
             updateIndex()
             if(loopTime == 0 || isDisplayedInScreen(self)==false){
@@ -123,17 +118,35 @@ public extension UIImageView{
     private func updateIndex(){
         self.syncFactor = (self.syncFactor+1)%gifImage.displayRefreshFactor!
         if(self.syncFactor==0){
-            self.displayOrderIndex = (self.displayOrderIndex+1)%self.gifImage.imageCount!
+            let displayOrderIndexNext = (self.displayOrderIndex+1)%self.gifImage.imageCount!
+            if(self.gifImage.displayOrder![displayOrderIndexNext] == self.gifImage.displayOrder![self.displayOrderIndex]){
+                self.sameFrameCheck = true
+            }else{
+                self.sameFrameCheck = false
+            }
+            self.displayOrderIndex = displayOrderIndexNext
             if(displayOrderIndex==0){
                 self.loopTime -= 1;
             }
         }
     }
+    
+    public func updateFrame(){
+        if(self.haveCache==false){
+            self.currentImage = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,self.gifImage.displayOrder![self.displayOrderIndex],[(kCGImageSourceShouldCacheImmediately as String): true])!)
+        }else{
+            if let image = (cache.objectForKey(self.displayOrderIndex) as? UIImage){
+                self.currentImage = image
+            }else{
+                self.currentImage = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,self.gifImage.displayOrder![self.displayOrderIndex],[(kCGImageSourceShouldCache as String): false])!)
+            }//prevent case that cache is not ready
+        }
+    }
 
     private func prepareCache(){
         self.cache.removeAllObjects()
         for i in 0..<self.gifImage.displayOrder!.count {
-            let image = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,self.gifImage.displayOrder![i],nil)!)
+            let image = UIImage(CGImage: CGImageSourceCreateImageAtIndex(self.gifImage.imageSource!,self.gifImage.displayOrder![self.displayOrderIndex],[(kCGImageSourceShouldCacheImmediately as String): true])!)
             self.cache.setObject(image,forKey:i)
         }
     }
@@ -199,6 +212,15 @@ public extension UIImageView{
             objc_setAssociatedObject(self, _haveCacheKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN);
         }
     }
+    
+    private var sameFrameCheck:Bool{
+        get {
+            return (objc_getAssociatedObject(self, _sameFrameCheckKey) as! Bool)
+        }
+        set {
+            objc_setAssociatedObject(self, _sameFrameCheckKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN);
+        }
+    }
 
     public var displaying:Bool{
         get {
diff --git a/JWAnimatedImage/JWAnimationManager.swift b/JWAnimatedImage/JWAnimationManager.swift
index 72ced45..c5a60d8 100644
--- a/JWAnimatedImage/JWAnimationManager.swift
+++ b/JWAnimatedImage/JWAnimationManager.swift
@@ -18,6 +18,7 @@ public class JWAnimationManager{
     private var memoryLimit:Int
     public var  haveCache:Bool
     
+    
     public init(memoryLimit:Int){
         self.memoryLimit = memoryLimit
         self.totalGifSize = 0