Hello,
Im a new AutoIt user, im from Spain and i would like to share here my own image search detection method.
What's about it?
It's not perfect, but with it you don't need to use any DLL file. You don't need to distribute the image file with your final AU3 Script, or Exe if compiled. The image size does not affect to the detection speed. It's bug free (i believe).
You can find here as an attach file, a distro package with all you need, and it includes a simple how-to guide.