IMRead() with IMReadUnchanged flag ignores EXIF orientation, when it should preserve it

[Alexn117]

It seems from the OpenCV documentation that the default behavior should be to preserve the EXIF orientation of an image, unless the IMReadIgnoreOrientation flag is set, but this is not happening.

When I use the following, to read a .png, the EXIF orientation is ignored:

img := gocv.IMRead(name, gocv.IMReadUnchanged)

But when I use IMReadColor, the orientation is preserved. This makes the .png lose it's transparency though:

img := gocv.IMRead(name, gocv.IMReadColor)

If EXIF information are embedded in the image file, the EXIF orientation will be taken into account and thus the image will be rotated accordingly except if the flag IMREAD_IGNORE_ORIENTATION is passed.
https://docs.opencv.org/master/d4/da8/group__imgcodecs.html#ga288b8b3da0892bd651fce07b3bbd3a56

IMREAD_IGNORE_ORIENTATION  | If set, do not rotate the image according to EXIF's orientation flag.
https://docs.opencv.org/master/d4/da8/group__imgcodecs.html#ga61d9b0126a3e57d9277ac48327799c80