What does yellow tinting represent when using "color misaligned images" on iPhone/iOS

so--i switched o开发者_如何学JAVAn "color misaligned images" to improve drawing performance in our app. The documentation states:

Puts a magenta overlay over images whose source pixels aren't aligned to destination pixels

I don't know what the yellow means however. (There is a "Color Offscreen-Rendered" option that uses yellow... does "Color Misaligned Images" also turn on this option?)

Anybody know?

TIA

Magenta overlays are caused by subpixel misalignment, while yellow overlays are caused by stretching. Prior to iOS 4, Instruments used magenta for both.