About image rotator
Photos taken on a phone sometimes open sideways, and scanned pages often come out turned. Rotating by 90, 180 or 270 degrees, or flipping the picture, fixes the orientation.
Rotate or flip
Rotation turns the picture around its centre. Flipping makes a mirror image, horizontally (left and right swapped) or vertically (top and bottom swapped). Text in a flipped picture reads backwards, so flip only when you really need a mirror image.
Why a photo looks fine on the phone but sideways elsewhere
Cameras often store the pixels one way and add an orientation tag. Some programs obey the tag and others ignore it. Saving a rotated copy writes the correct orientation into the pixels themselves, so it looks right everywhere.
A worked example
A photo taken with the phone held sideways arrives rotated 90 degrees in a form. Rotate it 90 degrees clockwise and save a new copy, which has the correct orientation built into the pixels, so every viewer displays it upright.
