[digiKam-users] why is batch convert to bw so extremely slow?

[Maik Qualmann]

The cause is the set compression. The BQM has its own setting for compression, 
see the "Save Images" tab. The default is 9, here with a 20MB PNG it takes 
about 1 minute, at level 5 only 10 seconds. The compression settings are also 
saved when you save a workflow.

The Multicore setting is in the "Behavior" tab.

Maik

Am Mittwoch, 1. Juli 2020, 17:49:23 CEST schrieb Daniel Bauer:
> Am 01.07.20 um 16:08 schrieb Gilles Caulier:
> > Hi Daniel,
> > 
> > Did you activate Multicore support in BQM ?
> 
> Hi Gilles,
> 
> where do I find that setting?
> 
> > Le mer. 1 juil. 2020 à 16:07, Daniel Bauer <linux at daniel-bauer.com> a 
écrit :
> >> Am 01.07.20 um 07:42 schrieb Maik Qualmann:
> >>> Saving large PNG files takes so long, Gimp is not faster either. Are you
> >>> sure you saved it as a PNG in the editor and not as a JPG? If
> >>> versioning is active, "Save changes" creates a JPG depending on the
> >>> setting, which is very fast. If you want to have a JPG in BQM, you have
> >>> to attach the tool for saving in JPG at the end of the tools.
> >>> 
> >>> Maik
> >> 
> >> I use to work with png. The difference I see is between the batch tool
> >> and the edit tool. Of course, saving "save as png" takes a bit, but
> >> compared to the batch tool it is extremely much faster.
> >> 
> >> There is no versioning active. It reads the original png, converts to
> >> bw, then saves in a subfolder as png. This takes 2 to 3 minutes per
> >> image, which is really long.
> >> 
> >> Doing the same manually, also in digikam: in album click on image to
> >> open editor, color: convert to bw, save as png... is at least ten times
> >> faster, but needs a lot of clicks and is very boring - and ideal job for
> >> a batch process. But I had to do it manually because I didn't want to
> >> wait almost 3 hours...
> >> 
> >> I know that highly compressed png take more time, but in settings I have
> >> set png compression to 5, and I think, the batch process uses that
> >> compression, too. Or not?
> >> 
> >>> Am Dienstag, 30. Juni 2020, 20:11:56 CEST schrieb Daniel Bauer:
> >>>> Hi,
> >>>> 
> >>>> Sometimes I'd like to convert a complete album to bw. I added 69 color
> >>>> png of 30-40MB to a batch, selected convert to bw, save in new folder,
> >>>> run.
> >>>> 
> >>>> Each image takes more tan 2 minutes to convert. When I open it in
> >>>> editor, and click color->bw it works immediately, also saving the file
> >>>> is fast. But batch processing is so slow that it cannot be used.
> >>>> 
> >>>> Now I must go through the album in editor, click color->bw->save->next
> >>>> 68 times, which is not comfortable but at least 10 times faster :-(
> >>>> 
> >>>> Why?
> >> 
> >> --
> >> Daniel Bauer photographer Basel Málaga
> >> https://www.patreon.com/danielbauer
> >> https://www.daniel-bauer.com