Objective-c – jpg or png for UIImage — which is more efficient

cocoa-touchiphoneobjective cuiimage

I am grabbing an image from the camera roll and then using it for a while as well as save it to disk as a PNG on the iPhone. I am getting the odd crash, presumably due to out of memory.

Does it make a difference if I save it as PNG or JPG (assuming I choose note to degrade the quality in the JPG case)? Specifically:

is more memory then used by the UIImage after I reload it off of disk if I saved it as a PNG?
is it possible the act of saving as PNG uses up more memory transiently during the saving process?

I had been assuming the UIImage was a format neutral representation and it shouldn't matter, but I thought I should verify.

Best Answer

I am getting the odd crash, presumably due to out of memory

Then STOP WHAT YOU ARE DOING RIGHT NOW and first figure out if that's actually the cause of the crash. Otherwise there's a very good chance that you're chasing the wrong problem here, fixing a memory problem that doesn't exist while ignoring the real cause of the crash. If you want to fix a crash, start by figuring out what caused the crash. Following up on what's "presumably" the problem is a recipe for wasted time and effort.

Related Solutions

Iphone – How to save a png image to camera roll

First you have to add AssetsLibrary Framework, than like this:

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

UIImage *image = ... some image

[library writeImageDataToSavedPhotosAlbum: UIImagePNGRepresentation(image) metadata:nil completionBlock:nil];

Objective-c – How to compare two NSDates: Which is more recent

Let's assume two dates:

NSDate *date1;
NSDate *date2;

Then the following comparison will tell which is earlier/later/same:

if ([date1 compare:date2] == NSOrderedDescending) {
    NSLog(@"date1 is later than date2");
} else if ([date1 compare:date2] == NSOrderedAscending) {
    NSLog(@"date1 is earlier than date2");
} else {
    NSLog(@"dates are the same");
}

Please refer to the NSDate class documentation for more details.

Best Answer

Related Solutions

Iphone – How to save a png image to camera roll

Objective-c – How to compare two NSDates: Which is more recent

Related Topic