og:image what is logic for choice? I’d like to choose my image

I realize there are no settings, so if I my WP generates 10 different image sizes how does your plugin choose one for og:image ? is it always the original uploaded image url?

My problem: I upload larger images and my current og:image implementation sends the original large image, and seems Facebook’s compression of the image size results in a poor quality image in facebook. I’d rather choose one of my already generated image sizes for the og:image URL