HTML version of README for Live USB

Henry Hartley henryhartley at
Tue Sep 2 12:31:33 UTC 2008

Warren Togami wrote
>> Peter Scheie wrote:
>> >>
>> >> The GIMP should theoretically be able to do all this?
>> >
>> > Because I'm a command line kinda person at heart. ;-)  I was just
>> > thinking I could do a 'for' loop in the directory with all the
>> > image files to reduce them to 16-bit color.  Yes, one can script
>> > things with the Gimp, but I've never done it, but I have done
>> > some looping things with ffmpeg for some videos, and was just
>> > looking for something similar.
>> Image manipulation is really a less reasonable thing to use command
>> line tools upon unless you are doing mass automatic batch
>> processing.  In the case of image manipulation where you are trying
>> to achieve small file sizes without dramatic reductions in quality,
>> it makes a WHOLE LOT more sense to use something like GIMP where
>> you can adjust parameters and instantly see (without saving) how
>> much it degrades the image?

As a photographer who uses either GIMP or Photoshop to make very subtle adjustments to images, I agree in general.  The thing is that you need to make slightly different adjustments to each image.  For instance, the changes to "Levels" between two almost identical images is going to be very slightly different.

When converting images from one bit depth to another, however, there aren't really any "settings" other than the target bit depth and in this case, that setting will be the same for all images.  ImageMagick is quite good at doing this sort of thing and I'd just loop through the files feeding them into this in some form.

convert -depth 16 old.png new.png

To be honest, I often make adjustments to large batches of images using command line tools.  Then, when I've found the few images I want to turn into enlargements or whatever, I go back to the originals and do everything by hand for those few images.  It's just too time consuming to do that with every image.

In this case, the images are all pretty similar in terms of size, color palette and contrast, etc.  I would guess that you could find (manually) the adjustments that work for one image and apply them to all images fairly safely.  You might need to go through the process two or three times to get things just right but you've still done less work than editing every image manually.


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