Recently in some app, we have significantly reduced the size of the IPA file that we send to Apple.
We develope an app with a lot of graphic content an we have reduced about 60% the size of the packet  sent to Apple, the so-called bundle file.

When you develop a universal iPad / iPhone app, and, above all, if you want to add support for viewing the retina to the new iPad 3, we can rest with the Size of the package rather excessive.
Many apps are designed for a multitude of textures in full screen, this is because many designers prefer to illustrate their ideas as better. These images, if you think iPad 3, for the dimesion of 2048 x 1536, yhe PNGs can be very heavy. The conversion of some of these images in JPEG format will save a lot of space.
It ‘a shame that the jpeg does not load faster, but some NPCs may also be more than 10MB, when they are in jpeg converted tha weigh is about ~ 200Kb.
This is a good first step, but you have to be very careful to avoid damaging the quality.

The conversion from png to jpg is not enough: after you convert as many great texture, the weight of the bundle IPA can still be consistent.
Our goal is to be almost always under 20 MB so  the old devices can download the app even without the WiFi.

 

ImageOptim: Basterà lanciare al suo interno la singola immagine o anche un gruppo, e saranno immediatamente compressi senza ridurre la qualità . Si riduce in media di circa il 15–35 %

Reading between the different sites I found some useful tips in the blog of Sam Soffes (http://samsoff.es/posts/image-optimization-on-ios) in his article recommends the use of ImageOptim, a small program that optimizes images. With this app for the Mac osx Tiflis are processed so as to occupy less disk space and so they can be loaded more quickly,” through the use of providing the best compression parameters to remove unnecessary comments and color profiles. The software handles PNG, JPEG and GIF animation.
ImageOptim integrates the various optimization tools: PNGOUT, AdvPNG, pngcrush, extended OptiPNG, jpegoptim, jpegrescan, and jpegtran Gifsicle.
Particularly suitable for publishing images on the web (shrinks images easily “saved” for the Web in Photoshop) is useful for creating applications rivelto Mac and iPhone / iPad ever read.

Also you can convert many images as PNG8, Photoshop, under File> Save for Web & ‘can export as PNG24 PNG8 instead of those images that are fine as GIF. Even if it does not support alpha variable, is ideal for simple images.

Sam considers ImageOptim even fantastic, processes the images through a series of tools squeezing as much as possible and without reducing quality. Even if you saved “for-web” all images, ImageOptim is able to compress more than 50%. Some files have a dramatic reduction up to 90%.

Sam has processed all the images through ImageOptim twice. The second time it was able to compress some images even more in depth.
It ‘important to note that this is all done in lossless compression.

 

It is possible to make the images even more read ImageAlpha (from the creators of ImageOptim). It is a tool that allows you to create PNG8 images with alpha variable.
This will save a lot of space. This is a more manual process than ImageOptim, but it works well to enlarge the images with alpha that does not have a lot of colors.

Note: Be sure to turn off image optimization Xcode or you will undo all your hard work when crerete your bundle.

Conclusion

We have heard mixed reviews on these products. Some claim to have had problems with these instruments, while others are fully satisfied.
In our experience it works quite well;
if you are trying to reduce the size of the app (bundle), then we recommend that you use these tools.

For the most ‘experts:
If you want to try to make an even higher compression, you can try to use the fork di Scribd del AdvanceCOMP John Englehart (the creator of JSONKit);
it is a product a little too hardcore, but we would recommend to most people-‘-geeks give it a try.