[Digikam-devel] Non-destructive image editing

[Mikolaj Machowski]

On Friday 17 July 2009 07:48:03 Gilles Caulier wrote:
> There is 2 way to apply non-destructive photo editing :
>
> 1 save resulting images in a queue of tmp file (PNG is the best
> format) and register this queue to database .In digiKam GUI, use can
> see a preview of each version and choose the right in workflow.
> Problem is space consuming, but it's fast.

Even with modern storage space it may be too space consuming. This feature 
will be needed mostly for advanced amateurs up which use dSLR cameras with big 
pixel count and RAW format, resulting in big TIFF/PNG files.

Yesterday I got 60 MB 16-bit PNG from 6Mpx camera - and 6Mpx is small by today 
standards. Before printing I rotated it, corrected distorsion, cropped, small 
curves correction and again rotated to fit on page for printing. I have 
original after developing from RAW + 5 versions = 6 images -> ca. 330 MB for 
one image if storing all versions (6*60 - x for cropped version).

Of course digiKam could go for overkill - advanced history management: store 
all versions on disk for current work, clean them (all or selected) when fast 
access to intermediate steps isn't necessary, etc.

> 2 register in database and in image metadata (XMP media management
> namespace) all actions in editor (Actions List). When image is save,
> only list is recorded : in this case space is preserved, but time to
> restore image can be long because we need to replay all registered
> actions in editor.

To makes things faster you could store on disk original and last version of 
image. This way you can immediately load current version of image (which 
really 90% of users only need) and recreate with processing any step between.

Also digiKam could store JPG (or PGF) thumbnails of all versions between for 
quick visual navigation in image history. Note that those "thumbnails" doesn't 
have to be small in dimensions just compressed. Load 1:1 JPG/PGF copy of image 
and process "real" PNG in background.

m.