This is about the slickest thing I have seen in some time. And cheap too, at $12.
http://www.accurateshooter.com/technical-articles/ontarget-software-measures-groups/
I downloaded the free trial version and after playing around with it some, I bought it. It took a bit of fiddling to get it to measure my group correctly. OK, so it didn't do it right until after I read the tips. :
I confess that I didn't read any of the instructions at first or watch the demonstration.
The problem was that I was working from a picture of a target, and if you do it that way you have to start by establishing a reference to a known dimension on the group you are measuring. Like the measured extreme spread, grid spacing, etc. You just click on the +--+ icon in the controls bar, then click the cursor on your two measured points. Then a window pops up and you input your known measurement in it. Presto, you are in business. The tips say that if you start with a scan of the target/group you don't have to do that step.
I used the extreme spread measurement of a group on one of my 600 yard match targets from the match last Saturday, as it was scored at the match. By clicking the +---+ icon, then clicked the cursor in the centers of the two extreme spread holes, I then entered that value in the reference window. After that it was simple because the bullet placement cursor's circle was the same size as the black outline of the actual bullet holes on the picture of the target. OnTarget's measurement came up within .006 of the official 2.772 inch measurement of the group. That's pretty darned close; well inside the human judgement of aligning the tips of a micrometer on the bullet holes. At least, I think it is.
The tips page says this program is not intended for use in officially scoring targets. I don't disagree with that. But it sure is a feature packed program, cheap and slick as all get out.
To Benjamin199 and Wayne (bozo). Thanks for the link.
http://www.accurateshooter.com/technical-articles/ontarget-software-measures-groups/
I downloaded the free trial version and after playing around with it some, I bought it. It took a bit of fiddling to get it to measure my group correctly. OK, so it didn't do it right until after I read the tips. :

The problem was that I was working from a picture of a target, and if you do it that way you have to start by establishing a reference to a known dimension on the group you are measuring. Like the measured extreme spread, grid spacing, etc. You just click on the +--+ icon in the controls bar, then click the cursor on your two measured points. Then a window pops up and you input your known measurement in it. Presto, you are in business. The tips say that if you start with a scan of the target/group you don't have to do that step.
I used the extreme spread measurement of a group on one of my 600 yard match targets from the match last Saturday, as it was scored at the match. By clicking the +---+ icon, then clicked the cursor in the centers of the two extreme spread holes, I then entered that value in the reference window. After that it was simple because the bullet placement cursor's circle was the same size as the black outline of the actual bullet holes on the picture of the target. OnTarget's measurement came up within .006 of the official 2.772 inch measurement of the group. That's pretty darned close; well inside the human judgement of aligning the tips of a micrometer on the bullet holes. At least, I think it is.
The tips page says this program is not intended for use in officially scoring targets. I don't disagree with that. But it sure is a feature packed program, cheap and slick as all get out.
To Benjamin199 and Wayne (bozo). Thanks for the link.