iPhone OS: Strategies for high density image work
- by Jasconius
I have a project that is coming around the bend this summer that is going to involve, potentially, an extremely high volume of image data for display. We are talking hundreds of 640x480-ish images in a given application session (scaled to a smaller resolution when displayed), and handfuls of very large (1280x1024 or higher) images at a time.
I've already done some preliminary work and I've found that the typical 640x480ish image is just a shade under 1MB in memory when placed into a UIImageView and displayed... but the very large images can be a whopping 5+ MB's in some cases.
This project is actually be targeted at the iPad, which, in my Instruments tests seems to cap out at about 80-100MB's of addressable physical memory.
Details aside, I need to start thinking of how to move huge volumes of image data between virtual and physical memory while preserving the fluidity and responsiveness of the application, which will be high visibility.
I'm probably on the higher ends of intermediate at Objective-C... so I am looking for some solid articles and advice on the following:
1) Responsible management of UIImage and UIImageView in the name of conserving physical RAM
2) Merits of using CGImage over UIImage, particularly for the huge images, and if there will be any performance gain
3) Anything dealing with memory paging particularly as it pertains to images
I will epilogue by saying that the numbers I have above maybe off by about 10 or 15%. Images may or may not end up being bundled into the actual app itself as opposed to being loaded in from an external server.
