Performance - UICollectionView Loading time very slow

Question

I am writing an app that takes a picture using the iDevice camera and stores it on the file system as a PNG. When starting my app, I load a UICollectionView with the images found on the file system.

The issue I am facing is that the load time for the app (even when its only loading 6 images is approximately 4 seconds which is unacceptable. I have implemented GCD to load images on a background thread (which keeps the UI snappy) however I really want the app to start far quicker with images loaded.

My thoughts are:

I suspect the initWithContentsOfFile is taking ages to load the full size image. I thought about generating a separate thumbnail image when a picture is taken and load that instead.

Ultimately when I look at Apple's Photo app, it loads "instantly" and has 10's of pictures in view.

Does anyone have any suggestions for how I can load the images faster or at least appear to?

Thanks!

Probably not in the first load, but `imageNamed` performs caching while the latter doesn't. — Adithya, Mar 25 '14 at 10:20
Ah ok thanks. I do having separate caching code, its the initial load that's the main problem. — Spanners, Mar 25 '14 at 10:22
Have you tried it in the device? And how big are the images? If they are pretty big in size, there is not much you can do other than load them asynchronously. — Adithya, Mar 25 '14 at 10:29
Yes I am running on the device and yes the images are normal image size (they are coming from the device's camera). — Spanners, Mar 25 '14 at 10:33

score 0 · Answer 1 · edited Nov 14 '16 at 13:52

0

Try this

Load image in background thread and set in main thread

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{

    UIImage *image = [UIImage imageWithContentsOfFile:frontPath];

    dispatch_async(dispatch_get_main_queue(), ^{
        [self.frontButton setBackgroundImage:image forState:UIControlStateNormal];
    });
});

edited Nov 14 '16 at 13:52

iYoung

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answered Mar 25 '14 at 10:17

abhishekkharwar

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I do this in the - (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath method but the initial load of the view takes ages. – Spanners Mar 25 '14 at 10:20
its still taking time ?? – abhishekkharwar Mar 25 '14 at 10:21
1

Yes it is - because its the initial load that takes the time, not any reloading. – Spanners Mar 25 '14 at 10:33

score 0 · Answer 2 · answered Mar 25 '14 at 10:20

0

Check this sample code and try to get some idea from it https://developer.apple.com/library/ios/samplecode/lazytableimages/introduction/intro.html

answered Mar 25 '14 at 10:20

Sandeep Ahuja

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Read that this morning and I don't see which bit helps? Am I missing something? I understand I can put a placeholder image whilst the cells load, however that isn't what the Photo app does. – Spanners Mar 25 '14 at 10:23
@Spanners: see this project helps to download images from network and in your case images data is stored on your local db, so try to take idea from this.. Hope this helps you, otherwise refer to some lazy image loading tutorials on web might helps you. – Sandeep Ahuja Mar 25 '14 at 11:30

Performance - UICollectionView Loading time very slow

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