Do not convert images to JPEG when stored to disk for caching

This saves CPU and memory in all cases and alpha channel / image clearness if orignal format was PNG or GIF.

Author: Olivier Poitrey

SDImageCache.h

@@ -10,14 +10,15 @@
 
 @interface SDImageCache : NSObject
 {
-    NSMutableDictionary *memCache;
+    NSMutableDictionary *memCache, *storeDataQueue;
     NSString *diskCachePath;
     NSOperationQueue *cacheInQueue;
 }
 
 + (SDImageCache *)sharedImageCache;
 - (void)storeImage:(UIImage *)image forKey:(NSString *)key;
 - (void)storeImage:(UIImage *)image forKey:(NSString *)key toDisk:(BOOL)toDisk;
+- (void)storeImage:(UIImage *)image imageData:(NSData *)data forKey:(NSString *)key toDisk:(BOOL)toDisk;
 - (UIImage *)imageFromKey:(NSString *)key;
 - (UIImage *)imageFromKey:(NSString *)key fromDisk:(BOOL)fromDisk;
 - (void)removeImageForKey:(NSString *)key;

SDImageCache.m

@@ -25,6 +25,7 @@ - (id)init
         memCache = [[NSMutableDictionary alloc] init];
 
         // Init the disk cache
+        storeDataQueue = [[NSMutableDictionary alloc] init];
         NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
         diskCachePath = [[[paths objectAtIndex:0] stringByAppendingPathComponent:@"ImageCache"] retain];
 
@@ -72,6 +73,7 @@ - (void)dealloc
     [memCache release], memCache = nil;
     [diskCachePath release], diskCachePath = nil;
     [cacheInQueue release], cacheInQueue = nil;
+    [storeDataQueue release], storeDataQueue = nil;
 
     [[NSNotificationCenter defaultCenter] removeObserver:self];
 
@@ -105,25 +107,43 @@ - (NSString *)cachePathForKey:(NSString *)key
 
 - (void)storeKeyToDisk:(NSString *)key
 {
-    UIImage *image = [[self imageFromKey:key fromDisk:YES] retain]; // be thread safe with no lock
+    // Can't use defaultManager another thread
+    NSFileManager *fileManager = [[NSFileManager alloc] init];
 
-    if (image != nil)
+    NSData *data = [storeDataQueue objectForKey:key];
+    if (data)
     {
-        [[NSFileManager defaultManager] createFileAtPath:[self cachePathForKey:key] contents:UIImageJPEGRepresentation(image, (CGFloat)1.0) attributes:nil];
-        [image release];
+        [fileManager createFileAtPath:[self cachePathForKey:key] contents:data attributes:nil];
+        @synchronized(storeDataQueue)
+        {
+            [storeDataQueue removeObjectForKey:key];
+        }
+    }
+    else
+    {
+        // If no data representation given, convert the UIImage in JPEG and store it
+        // This trick is more CPU/memory intensive and doesn't preserve alpha channel
+        UIImage *image = [[self imageFromKey:key fromDisk:YES] retain]; // be thread safe with no lock
+        if (image)
+        {
+            [fileManager createFileAtPath:[self cachePathForKey:key] contents:UIImageJPEGRepresentation(image, (CGFloat)1.0) attributes:nil];
+            [image release];
+        }
     }
+
+    [fileManager release];
 }
 
 #pragma mark ImageCache
 
-- (void)storeImage:(UIImage *)image forKey:(NSString *)key
+- (void)storeImage:(UIImage *)image imageData:(NSData *)data forKey:(NSString *)key toDisk:(BOOL)toDisk
 {
-    [self storeImage:image forKey:key toDisk:YES];
-}
+    if (!image || !key)
+    {
+        return;
+    }
 
-- (void)storeImage:(UIImage *)image forKey:(NSString *)key toDisk:(BOOL)toDisk
-{
-    if (image == nil || key == nil)
+    if (toDisk && !data)
     {
         return;
     }
@@ -132,10 +152,23 @@ - (void)storeImage:(UIImage *)image forKey:(NSString *)key toDisk:(BOOL)toDisk
 
     if (toDisk)
     {
+        [storeDataQueue setObject:data forKey:key];
         [cacheInQueue addOperation:[[[NSInvocationOperation alloc] initWithTarget:self selector:@selector(storeKeyToDisk:) object:key] autorelease]];
+
     }
 }
 
+- (void)storeImage:(UIImage *)image forKey:(NSString *)key
+{
+    [self storeImage:image imageData:nil forKey:key toDisk:YES];
+}
+
+- (void)storeImage:(UIImage *)image forKey:(NSString *)key toDisk:(BOOL)toDisk
+{
+    [self storeImage:image imageData:nil forKey:key toDisk:toDisk];
+}
+
+
 - (UIImage *)imageFromKey:(NSString *)key
 {
     return [self imageFromKey:key fromDisk:YES];
@@ -152,7 +185,7 @@ - (UIImage *)imageFromKey:(NSString *)key fromDisk:(BOOL)fromDisk
 
     if (!image && fromDisk)
     {
-        image = [[UIImage alloc] initWithData:[NSData dataWithContentsOfFile:[self cachePathForKey:key]]];
+        image = [[UIImage alloc] initWithContentsOfFile:[self cachePathForKey:key]];
         if (image != nil)
         {
             [memCache setObject:image forKey:key];

SDWebImageDownloader.h

@@ -20,6 +20,7 @@
 
 @property (nonatomic, retain) NSURL *url;
 @property (nonatomic, assign) id<SDWebImageDownloaderDelegate> delegate;
+@property (nonatomic, retain) NSMutableData *imageData;
 
 + (id)downloaderWithURL:(NSURL *)url delegate:(id<SDWebImageDownloaderDelegate>)delegate;
 - (void)start;

SDWebImageDownloader.m

@@ -10,7 +10,6 @@
 
 @interface SDWebImageDownloader ()
 @property (nonatomic, retain) NSURLConnection *connection;
-@property (nonatomic, retain) NSMutableData *imageData;
 @end
 
 @implementation SDWebImageDownloader
@@ -73,16 +72,19 @@ - (void)connection:(NSURLConnection *)aConnection didReceiveData:(NSData *)data
 
 - (void)connectionDidFinishLoading:(NSURLConnection *)aConnection
 {
-    UIImage *image = [[UIImage alloc] initWithData:imageData];
-    self.imageData = nil;
     self.connection = nil;
 
+    if ([delegate respondsToSelector:@selector(imageDownloaderDidFinish:)])
+    {
+        [delegate performSelector:@selector(imageDownloaderDidFinish:) withObject:self];
+    }
+
     if ([delegate respondsToSelector:@selector(imageDownloader:didFinishWithImage:)])
     {
+        UIImage *image = [[UIImage alloc] initWithData:imageData];
         [delegate performSelector:@selector(imageDownloader:didFinishWithImage:) withObject:self withObject:image];
+        [image release];
     }
-
-    [image release];
 }
 
 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

SDWebImageDownloaderDelegate.h

@@ -12,6 +12,7 @@
 
 @optional
 
+- (void)imageDownloaderDidFinish:(SDWebImageDownloader *)downloader;
 - (void)imageDownloader:(SDWebImageDownloader *)downloader didFinishWithImage:(UIImage *)image;
 - (void)imageDownloader:(SDWebImageDownloader *)downloader didFailWithError:(NSError *)error;
 

SDWebImageManager.m

@@ -120,7 +120,10 @@ - (void)imageDownloader:(SDWebImageDownloader *)downloader didFinishWithImage:(U
     if (image)
     {
         // Store the image in the cache
-        [[SDImageCache sharedImageCache] storeImage:image forKey:[downloader.url absoluteString]];
+        [[SDImageCache sharedImageCache] storeImage:image
+                                          imageData:downloader.imageData
+                                             forKey:[downloader.url absoluteString]
+                                             toDisk:YES];
     }
     else
     {