I find myself changing the desktop resolution of the SUT on occasion. I have dealt with software that deals with this specifically. Each time this is done, Eggplant fails because it cannot locate images captured on, for example, a 800x00 screen that you are currently running at 1024x768.
I think this could be resolved if a new Eggplant search method were added. It would work by searching for ratios of neighboring pixels. So, even if you change resolutions, the ratios would be the same.
This should not be happening. Eggplant scripts/images are resolution independent. I think that your script is failing for some other reason, perhaps the change in resolution forces something that had previously been on the screen to appear in a position where it needs to be scrolled to, or a window is repositioned so that it covers the image.
If you can’t find another reason for the failure, you can send the image that is not being found and the ScreenError.tiff file that is generated at the time of the failure to support (@redstonesoftware.com), and we can analyze the problem for you.
Your suggestion of a search type built on ratios more or less describes why we are resolution independent: The internal representation of the images is same – screen resolution is just a method of mapping each virtual pixel to a given number of physical pixels on the monitor.