I need to flip 1400 dng images horizontally, eg along a vertical axis, so that left becomes right as in a mirror.
With imagemagick, it works well with tif images, using "magick convert -flop". But on dng, there is a tricky delegation issue because of an outdated dng lib.
Is there another way to do it or should I solve this delegation issue (this is a one-time need)? I feel that others would find helpful to find an documented alternative.
I have tried quite a few utilities (cli and gui, linux and windows) but none allows the flipped image to be saved as dng. In Digikam for example, the flip is only a flag, the pixels are not flipped. In others, one needs to save as tif or jpg.
I can't test this with your downstream processing software, and it may well ignore the flag I am setting, but here's what I have for what it's worth.
If you use exiftool you can extract the "orientation" like this:
exiftool -orientation C02-322.dng
Orientation : Horizontal (normal)
Or if you go numeric instead of interpreted:
exiftool -n -orientation C02-322.dng
Orientation : 1
Then you can set the orientation. I set it to 2 or "mirrored horizontal" like this:
exiftool -IFD0:Orientation#=2 C02-322.dng
The values you can try are specified here.
I then checked again with:
exiftool -orientation C02-322.dng
Orientation : Mirror horizontal
I have no idea whether your downstream processing will respect this. The modified version of the file is of identical length, so I guess all your existing DNG data has been carried forward correctly.