What is happening when iTunes syncs images to the iPod touch?

I am developing an image processing app on the iPod touch. When syncing images from iTunes, I noticed that large images are scaled down. This causes the results to differ from the results in the simulator. I also noticed that the results differ, depending on whether I synced the images through iTunes on Windows or iTunes on Mac (regardless whether they were scaled or not开发者_Go百科).

Can someone explain to me, what iTunes is doing with my images?

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iTunes downsamples and converts images into a format more suitable for display on the device screen. This might include colorspace optimizations, screen calibrations, and color reduction done in the name of speed and size.

The platform differences might be able to be accounted for in framework/code differences in the libraries Apple ships with iTunes-windows.