Good question! It depends on how the image was turned. If it was turned only in a 2 dimensional way, as you would a physical photo, the image would be rotated. A 180' rotation would be upside down.
But electronic pictures, like photographic negatives, can be turned in 3 dimensions. "Flipping" is the typical word in this case. Real-life usage of "flipping" is sloppy, but it is generally used to refer to a 3-dimensional action, e.g. "I flipped the playing cards over to reveal their face." Flipping gives you a "mirror image". (1)
If the image is only rotated, in 2 dimensions - you could easily read it by rotating it back to the original viewing position. Your example might be flipped, and rotated to get it upside down. See the graphic I have provided.
You COULD use the word "opposite" - but it would need the proper context, and I do not think it conveys the meaning you want at all. "Opposite" would normally apply only to the images inside the picture - and not to the picture itself. Example: "The people are standing opposite their positions in the original!" This would be understood by most people to mean that the picture had been transposed, or flipped, from left to right. Head and foot oppositeness would be upside-down.
I have drawn up a graphic to illustrate rotating and flipping.
You should also look at the usage of "tranpose", as it is similar in usage. Flipping also transposes the elements of the picture. What was on the left is now on the right, or top/bottom, etc.
Notice that #4, flipped on a horizontal axis, would be the same effect as if you flipped on a vertical axis, and then rotated 180 degrees.
(1) I am ignoring the tense aspect of the verbs for this description. I think you will figure that out a-ok on your own.