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Re: [LUG] Bulk image conversion

 

Simon Robert wrote:
On Fri, 2010-01-29 at 15:16 +0000, Gordon Henderson wrote:
On Fri, 29 Jan 2010, Keith Abraham wrote:

I have a directory containing approx 100 colour images (.PNG) which I need to convert to grayscale.

I could convert each one individually using GIMP but I'm sure there must be a tool to do a bulk conversion.
Anyone know of such a tool (imagemagick?) and how to do the conversion?
You said it yourself: imagemagick - specifally the mogrify tool.

So start with

   man mogrify

and take it from there.

Take a copy first, as mogrify changes file in-place!


However, converting from colour to greyscale is a bit of a black art, depending on how "nice" you want it to be. There is a nice way to do it in GIMP, but it requires a few stages (rather than just pushing the greyscale button), but it all depends on how you want to capture contrasts, etc.

I use csh, so for me, I'd do: (on the copy!)

   foreach f (*.png)
     echo doing $f
     mogrify -type Grayscale $f
   end

I'm sure someone who knows bash can give the equivalent.

Gordon

I realise this isn't a neat and tidy command line solution, but digikam
the photo management app has a grey scale bulk conversion option - under
tools/colours. It doesn't seem to give you many options as to changing
the grey scale, but it will rename all the images and save originals
etc. It also has many other useful batch conversion tools.

It is a kde application, but will happily run on gnome, although a
distro with a repo manager that picks up all dependencies is helpful.
kipi plugins should be installed at the same time.

IMHO digikam is by far and away the best photo management/album tool
around. Better than commercial counterparts for other OS's and better
than f-spot its OSS counterpart for gnome.

f-spot doesn't have the range of basic photo editing options, or the
batch processing options. f-spot also has a confusing directory storage
structure which makes finding a pic difficult if you're not using
f-spot.

Picassa is OK, but doesn't have the editing/batch options and also seems
to pick up every image on your hard drive and networked machines rather
than those in a designated ../Photos/etc.... directory structure.

Simon

Thanks guys.

I tried using imagemagick but I couldn't write a script which worked (what I know about scripting is slightly less than zero).

In the end (thanks to Simon) I used Digikam. I must admit I didn't know about the batch processing facility. I couldn't find the Colours entry under the Tools menu until i realised I had to install the kipi-plugins package. Everything was plain sailing from there on.

The quality is so-so. Some of the images have text captions and the lettering is "smeared" (I might have to use Gimp for these). But IMHO the graphics quality of the images is sufficient for website use.

I agree Simon Digikam is a good application and finding the plugins package makes it a great application..

Gwenview also uses the kipi-plugins and can therefore do most of the effects, conversions etc. as DigiKam.

Keith




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