jder · March 20, 2018 06:51 · May 6, 2014 · Dec 18, 2012 · Dec 18, 2012 · Dec 18, 2012
diff --git a/Downscaling ALAssets b/Downscaling ALAssets
@@ -1,4 +1,4 @@
-// See http://mindsea.com/2012/12/18/downscaling-huge-alassets-without-fear-of-sigkill for details
+// For details, see http://mindsea.com/2012/12/18/downscaling-huge-alassets-without-fear-of-sigkill
 
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <ImageIO/ImageIO.h>

diff --git a/Downscaling ALAssets b/Downscaling ALAssets
@@ -3,7 +3,7 @@
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <ImageIO/ImageIO.h>
 
-// Helper methods for thumbnailForAsset:ofSize:
+// Helper methods for thumbnailForAsset:maxPixelSize:
 static size_t getAssetBytesCallback(void *info, void *buffer, off_t position, size_t count) {
     ALAssetRepresentation *rep = (__bridge id)info;
 
@@ -12,14 +12,14 @@ static size_t getAssetBytesCallback(void *info, void *buffer, off_t position, si
 
     if (countRead == 0 && error) {
         // We have no way of passing this info back to the caller, so we log it, at least.
-        NSLog(@"thumbnailForAsset:ofSize: got an error reading an asset: %@", error);
+        NSLog(@"thumbnailForAsset:maxPixelSize: got an error reading an asset: %@", error);
     }
 
     return countRead;
 }
 
 static void releaseAssetCallback(void *info) {
-    // The info here is an ALAssetRepresentation which we CFRetain in thumbnailForAsset:ofSize:.
+    // The info here is an ALAssetRepresentation which we CFRetain in thumbnailForAsset:maxPixelSize:.
     // This release balances that retain.
     CFRelease(info);
 }
@@ -28,7 +28,7 @@ static void releaseAssetCallback(void *info) {
 // The resulting UIImage will be already rotated to UIImageOrientationUp, so its CGImageRef
 // can be used directly without additional rotation handling.
 // This is done synchronously, so you should call this method on a background queue/thread.
-- (UIImage *)thumbnailForAsset:(ALAsset *)asset ofSize:(NSUInteger)size {
+- (UIImage *)thumbnailForAsset:(ALAsset *)asset maxPixelSize:(NSUInteger)size {
     NSParameterAssert(asset != nil);
     NSParameterAssert(size > 0);
 

diff --git a/Downscaling ALAssets b/Downscaling ALAssets
@@ -1,4 +1,4 @@
-// See http://mindsea.com/?p=1426 for details
+// See http://mindsea.com/2012/12/18/downscaling-huge-alassets-without-fear-of-sigkill for details
 
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <ImageIO/ImageIO.h>

diff --git a/...ing Huge ALAssets Without Fear of SIGKILL → Downscaling ALAssets b/...ing Huge ALAssets Without Fear of SIGKILL → Downscaling ALAssets
diff --git a/Downscaling Huge ALAssets Without Fear of SIGKILL b/Downscaling Huge ALAssets Without Fear of SIGKILL
@@ -0,0 +1,65 @@
+// See http://mindsea.com/?p=1426 for details
+
+#import <AssetsLibrary/AssetsLibrary.h>
+#import <ImageIO/ImageIO.h>
+
+// Helper methods for thumbnailForAsset:ofSize:
+static size_t getAssetBytesCallback(void *info, void *buffer, off_t position, size_t count) {
+    ALAssetRepresentation *rep = (__bridge id)info;
+
+    NSError *error = nil;
+    size_t countRead = [rep getBytes:(uint8_t *)buffer fromOffset:position length:count error:&error];
+
+    if (countRead == 0 && error) {
+        // We have no way of passing this info back to the caller, so we log it, at least.
+        NSLog(@"thumbnailForAsset:ofSize: got an error reading an asset: %@", error);
+    }
+
+    return countRead;
+}
+
+static void releaseAssetCallback(void *info) {
+    // The info here is an ALAssetRepresentation which we CFRetain in thumbnailForAsset:ofSize:.
+    // This release balances that retain.
+    CFRelease(info);
+}
+
+// Returns a UIImage for the given asset, with size length at most the passed size.
+// The resulting UIImage will be already rotated to UIImageOrientationUp, so its CGImageRef
+// can be used directly without additional rotation handling.
+// This is done synchronously, so you should call this method on a background queue/thread.
+- (UIImage *)thumbnailForAsset:(ALAsset *)asset ofSize:(NSUInteger)size {
+    NSParameterAssert(asset != nil);
+    NSParameterAssert(size > 0);
+
+    ALAssetRepresentation *rep = [asset defaultRepresentation];
+
+    CGDataProviderDirectCallbacks callbacks = {
+        .version = 0,
+        .getBytePointer = NULL,
+        .releaseBytePointer = NULL,
+        .getBytesAtPosition = getAssetBytesCallback,
+        .releaseInfo = releaseAssetCallback,
+    };
+
+    CGDataProviderRef provider = CGDataProviderCreateDirect((void *)CFBridgingRetain(rep), [rep size], &callbacks);
+    CGImageSourceRef source = CGImageSourceCreateWithDataProvider(provider, NULL);
+
+    CGImageRef imageRef = CGImageSourceCreateThumbnailAtIndex(source, 0, (__bridge CFDictionaryRef) @{
+                                                                  (NSString *)kCGImageSourceCreateThumbnailFromImageAlways : @YES,
+                                                                  (NSString *)kCGImageSourceThumbnailMaxPixelSize : [NSNumber numberWithInt:size],
+                                                                  (NSString *)kCGImageSourceCreateThumbnailWithTransform : @YES,
+                                                              });
+    CFRelease(source);
+    CFRelease(provider);
+
+    if (!imageRef) {
+        return nil;
+    }
+
+    UIImage *toReturn = [UIImage imageWithCGImage:imageRef];
+
+    CFRelease(imageRef);
+
+    return toReturn;
+}