Memory usage goes through the roof when adding UIImageViews

[eagerterrier]

I have a project where I am asynchronously loading images from my site. All was working fine, until I started doing a gallery view for the app, when I noticed that the memory usage went through the roof when I add a bunch of small images.

I was trying storing images on file and also in memory with no change.

Typically, the app bumbles along for c.2Mb until I hit the gallery page, when it shoots up to 5Mb and then up to 10Mb on the gallery detail page.

The weird thing is that when I add the images on the 5Mb-10Mb jump I am adding just 3 images of c.130Kb

Also, when I comment out the line

[self addSubview:async_imageView];

Memory stays low. So, it is not the getting the image and storing it in a finite cache that is causing the image, but rather displaying it in the view: Everything is released where it should be and I can't see where I can alter the code to avoid memory issues.

Anyone have any suggestions as to what I might try next?


Many thanks.

[scotopia]

What are the pixel dimensions of the images you are displaying?

[eagerterrier]

Originally Posted by scotopia

What are the pixel dimensions of the images you are displaying?

570 wide, flexi height - not massive by any means...

[scotopia]

Originally Posted by eagerterrier

570 wide, flexi height - not massive by any means...

Hmm...that might account for what you are seeing. In memory this will round up to a 1024x1024 texture, which is 2MB of RAM for a single image of this size right there.

[eagerterrier]

Dammit. I thought that only applied when you had either side of your view (imageview/scrollview etc) larger that 1024. The largest one I have that I can see is 575x879. All the rest are smaller.

I'm not keen on using CATiledLayer. Do you know what the best procedure is for dealing with images of this size? I guess just respond well to didReceiveMemoryWarning?

I'm thinking of removing any images not on the screen from the superview and maybe removing images from the cache also (although this seems like overkill in this situation as they are only taking up 140K each)

I have a 400 wide image option. I've tried using this instead and it's now down to a jump up to 9Mb.


thanks, scotopia

[scotopia]

No problem. Yeah, in memory any images round up to the smallest power of 2 square texture containing your dimensions; so unfortunately a 513x1 becomes a 1024x1024 in memory. Anything you can do to reduce the number of images displayed simultaneously or shrink things down to the next threshold (512x512 in this case) would help.

[eagerterrier]

Originally Posted by scotopia

No problem. Yeah, in memory any images round up to the smallest power of 2 square texture containing your dimensions; so unfortunately a 513x1 becomes a 1024x1024 in memory. Anything you can do to reduce the number of images displayed simultaneously or shrink things down to the next threshold (512x512 in this case) would help.

Right, now you've said this, that makes sense.

In my gallery detail viewcontroller, I am laying blank pages out in a row horizontally using pagination. So when I have no images in there, everything is fine.

I then load up the image the user has requested and one each side. When they scroll one way or the other, I am loading up another image in the direction they are going.

So, it's not the individual images themselves, but the fact that I am loading three at once, which makes the scrollview container, *way* bigger than 1024x1024.

I guess I load up just one image at a time and remove the others from superview on scroll. Not ideal by any means, but at least the app won't crash.

Thanks, scotopia, you've been a great help

[scotopia]

No problem; good luck!