Does the iPhone compress images saved within my app's documents directory?
- by Jane Sales
We are caching images downloaded from our server. We write them to our local storage like this:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0] ;
NSString* folder = [[documentsDirectory stringByAppendingPathComponent:@"flook.images"] retain];
NSString* fileName = [folder stringByAppendingFormat:@"/%@", aBaseFilename];
BOOL writeSuccess = [anImageData writeToFile:fileName atomically:NO];
The downloaded images are always the expected size, around 45-85KB.
Later, we read images from our cache like this:
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0] ;
NSString* folder = [[documentsDirectory stringByAppendingPathComponent:@"flook.images"] retain];
NSString* fileName = [folder stringByAppendingFormat:@"/%@", aBaseFilename];
image = [UIImage imageWithContentsOfFile:fileName];
Occasionally, the images returned from this cache read are much smaller because they are much more compressed - around 5-10KB. Has the OS done this to us?
