[Digikam-devel] virtual rotation of image...

Julien Narboux Julien at narboux.fr
Mon Jun 1 11:01:45 CEST 2009


Gilles,

Gilles Caulier a écrit :
> Marcel, The problem is more complex than this.
>
> We cannot use only one BD flag to set orientation of image. Why ? 
> because image representation in digiKam is taken from different place.
>
> I will take an ex with RAW file which are more complex case. For ex, 
> with my Dynax 5D camera, MRW as an embeded preview (a 640*480 JPEG 
> file). This preview is used to display thumbs in icon view and preview 
> of raw in embeded view mode.
>
> If i take a vertically oriented image with my camera, the preview on 
> camera screen is generally badly oriented and image is displayed 
> vertically with screen oriented horizonally. It's not optimum 
> especially with small screen from camera.
>
> So generaly i decide to rotate preview with my camera to judge if 
> image is valid or not. This modifity preview image orientation in 
> Minolta Makernote. This have side effect in digiKam : all are badly 
> oriented...

I think we should consider this as a problem of your Minolta camera : it 
should  rotate  the preview only virtually when displayed on the camera, 
and even better it should have a gravity sensor to do it on the fly as 
iphone does...
>
> To solve this problem, KPhotoAlbum use a databse flag for thumb. The 
> user can adjust it without to touch the file. I think we must do the same.

Why not have a small tool called "Uniformize preview and real picture 
orientation" which would treat a list of picture to set the same 
orientation to  both the preview and the real picture (when the picture 
is not square it is easy to do by looking at the longest side). The user 
would have the possibility to choose either to use preview orientation 
or real picture orientation. In your case you would choose real picture 
orientation.

Concerning rotation I think we have four cases:

-1- picture can not modified at all
-2- we can modify metadata but not the picture
-3- we can modify the picture, and the picture is stored in a format 
which allows lossless rotation
-4- we can, modify the picture but the picture is stored in a format 
which does not allow lossless rotation

In case 1 a dataflag  could be used. The image will apppear to be 
rotated only within Digikam.
In case 2 the exif flag could be used.
In case 3, lossless rotation can be used if we have time otherwise 
metadata if we want to have a quicker process.
In case 4 the exif flag could be used.

In all cases, I think that embedded preview, Digikam preview, jpeg and 
raw files orientation should be synchronized, otherwise it would confuse 
the user.

Best,

Julien



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