Interesting... :thinking_face: Did you know? When...

# random

[Stefan Oltmann]

Interesting... 🤔
Did you know?

When you rotate an image in Apple Photos, it doesn't adjust the orientation flag of the JPEG (for lossless rotation). Instead, it saves a rotated version as an edited image. When you export it, all metadata is transferred, and the orientation flag is always reset to "Standard."

This is probably better for compatibility with a wide range of devices, as there were times when viewers and browsers didn't consider this flag in the past.

However, it has consequences:
1. In the phone's storage, the image is then duplicated because Apple Photos keeps the original and, if applicable, an edited version for each photo.
2. Resetting edits (e.g., color corrections) also rotates the image back.
3. Resaving as JPG results in a loss of quality.
Changes to the capture date, location, or favorite marking are only reflected in the metadata.

Apple Photos respects the orientation flag of JPG when initially reading a file. If you change the orientation in the metadata afterward, nothing happens. Therefore, apps like Ashampoo Photos, as well as others I've tested (e.g., HashPhotos), need to save a new JPG as an edited version when rotating a photo.

By the way, it's always a JPG. Even if you rotate/edit a PNG, TIFF, or RAW, it's always saved as a JPG. You can test this by rotating a PNG and selecting "Share -> Notes".

I just wanted to share this with you. 😊

[ephemient]

https://jpegclub.org/jpegtran/

[ephemient]

lossless rotation of jpeg is possible as long as there are no partial MCUs (the image size is a multiple of 8x8 or 16x16 depending on color format)

[Stefan Oltmann]

Thank you for reminding me about the second option. However, it seems that Apple doesn't follow the same approach. When comparing to a JPEG rotated using the orientation flag I observe artifacts in the Beyond Compare pixel comparison.

[Stefan Oltmann]

Indeed this would be a nice feature in Ashampoo Photos to lossless rotate where Apple Photos can’t do it itself 🤔 I will add this to my backlog 😄