iPhone hangs when loading 100+ images in memory

There is a memory issue with the imageNamed: method. Try this instead:

[UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"myImage" ofType:@"png"]];

Did this help? I am also interested what what the memory limits are when it comes to images.

Message was edited by: lamouroux

Check the Apple Developer Forum where you posted the same question.

You're using up way too much memory with 100+ images. And yes they do take up more space than you think.

Are you releasing them without needing to? Note that imageWithContentsOfFile auto-releases, so when you add it to your array you don't need to release it.

The times I get weird crashes is when I released something I shouldn't have. When I get leaks, it's when I retained something I shouldn't have.

Hi, what exactly you're measuring in instruments? In my last app i first tried to fix the same kind of problem (low memory warning, than crash) with the object allocation and the leaks instrument. But for some reason my code HAD leaks which definitely were not detected by instruments. I than started to monitor the overall memory-usage of my app and check when or where it grows.

Well, because of the low memory warnings someone (the iPhone or instruments) must be wrong. 🙂
So i decided to check if the leaks instrument is wrong and looked for a different instrument to check the overall memory allocation of my app.
I found the memory monitor instrument which show the memory usage for alle the processes running on the device.
I than just repeated some specific funktions of my app and checked the memory usage of my app.
In my case for example i found a leak in my implementation of

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view

where i forgott to autorelease the returned view. This way i "lost" a UIView each time a new one was created for the UIPickewView. And the leaks instrument was not aware of that.

activity monitor should certainly show you the memory your app is using (select your app from the list below and check the memory used column.
Check the Free memory graph at the top of activity monitor. It will be going down to 2MB or less when getting memory warning.

100 images at one time is a lot.
width * height * 4 = number of bytes of memory per image. This is key. The size of the image compressed on disk has nothing to do with memory usage.
A single full frame image takes 614, 400 bytes (that's over 1/2 MB per image)
* 100 images = 61, 440, 000 bytes. (61 MB - more than you're likely to ever get)