Copy UImages from photo library to another directory

Question

I want to copy picture from the photo library to another directory in my app, every thing works just fine with the attached code here but when I try to copy a lot of images the app just crashes immediately I think that because the attached code is done with a single thread so each image needs its thread, so if there is too many pictures to copy the app crashes. I need the same code here but not in a thread that means the app should be blocked until the image is copied to the another directory , if any one have another good idea I would be appreciated. the for loop is saving each image.

for (int i = 0; i< countt ;i++) {

        NSURL *referenceURL = [self.ToSaveArray objectAtIndex:i];
        ALAssetsLibrary *assetLibrary=[[ALAssetsLibrary alloc] init];
        [assetLibrary assetForURL:referenceURL resultBlock:^(ALAsset *asset) {
            ALAssetRepresentation *rep = [asset defaultRepresentation];
            Byte *buffer = (Byte*)malloc(rep.size);
            NSUInteger buffered = [rep getBytes:buffer fromOffset:0.0 length:rep.size error:nil];
            NSData *data = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES];//this is NSData may be what you want
            NSLog(@"length %d",[data length]);
            UIImage *image= [UIImage imageWithData:data];
            [self SavePhoto:image withnum:i];
            //[data writeToFile:photoFile atomically:YES];//you can save image later
        } failureBlock:^(NSError *err) {
            NSLog(@"Error: %@",[err localizedDescription]);
        }];

    }

save photo code:

-(bool)SavePhoto:(UIImage *) imageTosave withnum:(int)num{


    float goodScal = imageTosave.size.width/75.0;

    CGSize newSize =CGSizeMake(imageTosave.size.width/goodScal, imageTosave.size.height/goodScal);
    UIImage* smallImage = [self resizeImage:imageTosave toSize:newSize];
    NSData *JpgDataS = UIImageJPEGRepresentation(smallImage, 1);
    NSData *JpgData = UIImageJPEGRepresentation(imageTosave, 1);



    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsPath = [paths objectAtIndex:0]; //Get the docs directory
    NSString *dataPath = [documentsPath stringByAppendingPathComponent:@"/CapturesPhotos"];
    NSDate *date = [NSDate date];
    NSDateFormatter *formatter = [[[NSDateFormatter alloc] init]autorelease];
    NSTimeZone *zone = [NSTimeZone localTimeZone];
    [formatter setTimeZone:zone];
    [formatter setDateFormat:@"yyyyMMddHHmmss"];
    NSString* Bnamee = [NSString stringWithFormat:@"/IMG%d_%@B.jpg",num,[formatter stringFromDate:date]];
    NSString* Snamee = [NSString stringWithFormat:@"/IMG%d_%@S.jpg",num,[formatter stringFromDate:date]];
    //NSString *filePath = [dataPath stringByAppendingPathComponent:namee]; //Add the file name
    NSString *filePath = [dataPath stringByAppendingPathComponent:Bnamee]; //Add the file name
    NSString *filePathS = [dataPath stringByAppendingPathComponent:Snamee]; //Add the file name
    [JpgData writeToFile:filePath atomically:YES]; //Write the file
    [JpgDataS writeToFile:filePathS atomically:YES]; //Write the file
    //[pngData writeToFile:filePath atomically:YES]; //Write the file
    return true;
}

thanks in advance

Answer 1

It seems likely that starting off that many asynchronous operations is running you out of memory, try serializing the expensive (memory-wise) parts of it using a serial queue:

dispatch_queue_t    queue = dispatch_queue_create("save", DISPATCH_QUEUE_SERIAL);

// Move this out of loop for efficiency
ALAssetsLibrary*    assetLibrary=[[ALAssetsLibrary alloc] init];

for (int i = 0; i< ToSaveArray.count ;i++) {

    NSURL *referenceURL = [ToSaveArray objectAtIndex:i];
    [assetLibrary assetForURL:referenceURL resultBlock:^(ALAsset *asset) {
        ALAssetRepresentation *rep = [asset defaultRepresentation];
        dispatch_async(queue, ^{

            Byte *buffer = (Byte*)malloc(rep.size);
            NSUInteger buffered = [rep getBytes:buffer fromOffset:0.0 length:rep.size error:nil];
            NSData *data = [NSData dataWithBytesNoCopy:buffer length:buffered freeWhenDone:YES];//this is NSData may be what you want
            NSLog(@"length %d",[data length]);
            UIImage *image= [UIImage imageWithData:data];
            [self SavePhoto:image withnum:i];
        });
        //[data writeToFile:photoFile atomically:YES];//you can save image later
    } failureBlock:^(NSError *err) {
        NSLog(@"Error: %@",[err localizedDescription]);
    }];

}

dispatch_async(queue, ^{
    // Some code to execute when all the saving is done
});

I'm not sure if this will actually solve the problem, but it's worth trying :)

Also, a corrected version of how to get the UIImage more cleanly (from this answer):

UIImage*            image = [UIImage imageWithCGImage:[rep fullResolutionImage]
                                                scale:[rep scale]
                                          orientation:UIImageOrientationUp];

Although in your case it's probably better to continue fetching the image data itself, just pass that into your save routine so you can save the expense of converting jpg->image->jpg. You still need to create the image so you can also save the thumbnail, but that's another matter.