Printscreen, then simply crop in mspaint to someting like 100x50 pixels.What did you make a picture of for lockbox.bmp?
My lockbox example:
The windows are transparent in the swtor gui though ... so in the lower part of the screen the background could be more blackish while high up more blueish.
You can change the tolerance of imagesearch, somewhere between 0 and 255. I used a 100, but that would sometimes still miss one if it was really low in the list. Play around with it.