Reducing iOS App file size
I have made a very simple iPhone app with Xcode 6.1 and swift. I am really new to ios developing and ran into an app which in the end is 134 mb! of course this is not acceptable.
I have background images for all screen sizes which add up to 20 mb. and thats it! I am storing those images in xcassets, as thats the preferred way I guess.
the app shouldnt have more than 25 mbs, I think.
I figured out that I had some references doubled in my project. I removed these and still my .app file is 89 mbs!
What am I doing wrong? I read several threads on this, but nothing really helped!
What I did until now:
- reduce the size of all pngs
- disable the compress PNG option, as it seems to make the PNGs bigger (lol)
- configured the build settings to run the fastest and smallest build
- Strip Debug Symbols During Copy build setting to Yes (COPY_PHASE_STRIP = YES)
edit1: Apparenty Xcode does something weird with my pngs. Some of those pictures, that are 2 mb originally, are more than 10mb in the .app-file. What does xcode do there ?
Answer
It is actually not surprising that the Apple recompressed files are bigger. They are optimized for fast load not small size. If you do not care about size over speed, defiantly do turn off the compression. Even if you do care about speed you can do better than Apple.
https://imageoptim.com/xcode.html
So yes, turn off the PNG compression. The first thing I would do is build the ipa. An ipa is actually a zip file so build the ipa, copy it to a folder on your mac, rename the file with a .zip extension and double click on it. This will expanded it. Find the app in the Payload folder and right mouse click on it and choose show package contents. You will see all the assets. Sort by size. I am guessing you have overly large images. At that size my guess is that the extra size is likely to be caused almost entirely by the PNG files.
Consider using non retina images for some. Honestly most people wont notice. iOS will gracefully use the non retina on retina. This can save a ton of space,
Also consider using jpeg files instead of PNG for some of the files if you do not need transparency. Jpeg files are less efficient but can be much smaller. Compare both. Depends on the extent to which the images are continuous tone.
By default PNG file are 32 bit. 24 bit color and 8 buit alpha/transparency. You can save a bit of size by going to 24 bit. You can also save a lot of size going to 16 bit color or below. At 8 bit PNG files use a color lookup table. Play with Photoshop and the save for we options at PNG with bit depth 8 and below.
I have all sorts of expensive compressing software but often use the $8
https://itunes.apple.com/us/app/lossless-photo-squeezer/id704083918?mt=12
Try the 8 bit PNG option and the JPEG options.
EDIT I did some research. I had always know Fireworks did better PNG compression. I did not realize that there was an 8bit PNG with an 8 Bit alpha channel. Photoshop supports 8 bit with a 1 bit Alpha Channel. I have always told people to use 32 bit PNG if their transparency needed more than 1 bit. In the future I will let them know the 8 bit with 8 bit alpha may be the better route, They just can use Photoshop for the final save of the file. They just need to save a 32 bit and compress elsewhere.
http://calendar.perfplanet.com/2010/png-that-works/
David