As long as you know the positions of the beginning of the move anims in the original image, all you need do is offset them by the number of frames in the original image.
i.e. if your original image is your character walking left, and it takes 10 frames, once you run it through my little program, the new image will be 20 frames, and you can just add 10 to make the character walk right.
i.e. if your original image is your character walking left, and it takes 10 frames, once you run it through my little program, the new image will be 20 frames, and you can just add 10 to make the character walk right.