When an image is taken in portrait mode (on a smartphone or digital camera) the image data itself in most cases is saved in landscape mode and a flag is added to the EXIF data, that the image should be displayed rotated (e.g. 90° CCW).
Some applications (like e.g. macOS Preview) evaluate the EXIF data and will display the image in the correct orientation. Browsers as well as PDFreactor however do not support evaluating EXIF data, so images which are only rotated using this data will not be displayed with the correct orientation. So in order to display those images with the correct orientation in Browsers and PDFreactor you have two options:
- Rotate the image by rotating the actual pixels, not by just changing the EXIF orientation
- Add a CSS "transform: rotate(90deg)" to the images that have the wrong orientation and should be rotated.