I appreciate your response, but ImageEvents is the interfaceless app on the Mac that is used by Applescript to automate the manipulation of images. Using Photo or Preview would not be practical in a scripting situation. And resizing literally hundreds of photos a day manually would not be feasible.
However, I did figure out a solution. ImageEvents resizing without creating a dark fuzzy edge around the result relies on a target size that is an even factor of the original size. So if the original is 600 pixels wide, there is no problem targeting 450 pixels, 300 pixels, 200, 100, 60, 50 etc. It's only a problem if there is a remainder in the math. ie, if the target size results in a fractional pixel width like 425 or 31. So I changed my scripts to work with that in mind.