11-21-2018, 03:26 PM
When you look only at the pixel data, the image from a camera is always in landscape mode. The EXIF orientation field specifies which of its four corners is actually the top-left one.
When you edit a portrait image(*), the image is rotated on load, and saved as a portrait image, while the orientation field is reset to indicate the top-left corner as the actual top-left (no rotation).
Normally Gimp does the right thing with the EXIF orientation when saving.
Historically the WinXP image viewer didn't use the EXIF, and so would show portrait images rotated on the side. When yo uused the rotate button, it would resave the rotated image (**) and to add insult to injury, would not change the EXIF orientation, so other viewers (or Gimp) would rotate the image again...
(*) or an upside-down one....
(**) which in itself is a capital sin, you shouldn't change the user data without an explicit order to do so
When you edit a portrait image(*), the image is rotated on load, and saved as a portrait image, while the orientation field is reset to indicate the top-left corner as the actual top-left (no rotation).
Normally Gimp does the right thing with the EXIF orientation when saving.
Historically the WinXP image viewer didn't use the EXIF, and so would show portrait images rotated on the side. When yo uused the rotate button, it would resave the rotated image (**) and to add insult to injury, would not change the EXIF orientation, so other viewers (or Gimp) would rotate the image again...
(*) or an upside-down one....
(**) which in itself is a capital sin, you shouldn't change the user data without an explicit order to do so