Pretty much as simple as it sounds. Sometimes, images presented in the gallery are hard to comprehend when viewed in their 'default' orientation. So, when viewing an image in gallery-mode, allowing the user to press the 'R' button or the 'L' button to rotate the image-orientation might be useful. That said, allowing for 'M' to cause image-appearances to 'mirror' might be useful, too.
Pretty much as simple as it sounds. Sometimes, images presented in the gallery are hard to comprehend when viewed in their 'default' orientation. So, when viewing an image in gallery-mode, allowing the user to press the 'R' button or the 'L' button to rotate the image-orientation might be useful. That said, allowing for 'M' to cause image-appearances to 'mirror' might be useful, too.