Bulk change image format

apokryphos · 09-04-2004, 04:24 PM

I know that there's a few programs out there to convert a particular image from one filetype (i.e. GIF), to another (JPEG), like the GIMP, but are there any programs that you can mass or rather, "bulk change" the format. That is, do many at a time.

I'm generally looking to change large JPEGs to smaller jpegs, probably of lower quality. Since I have many high-quality images coming from my camera, it would be nice to have a quicker/easier way to make them smaller and put them on the Internet. Is there any program like this for Linux?

Any help would be greatly appreciated.

Tinkster · 09-04-2004, 04:33 PM

man convert

You could use it with find or a bash-script.

Cheers,
Tink

apokryphos · 09-04-2004, 04:58 PM

Your help is much appreciated. I see that I can quite easily change the size of an image and change it to JPG, but quickly browsing through it, there doesn't seem to be a way to do many at a particular time. Say, wanting it to convert all the images in a folder.

Since, it seems to only allow doing one at a time, and you need ot specify a new name for it each time. Sorry for the hassle.

Tinkster · 09-05-2004, 12:58 AM

As I said ;)

http://www.linuxquestions.org/questi...230#post534230

David (co-mod) has done a nice little script :)

Just add the resize and voila.

Cheers,
Tink

Electro · 09-05-2004, 03:22 AM

Re-saving JPG to a much higher compression ratio will make the picture look very blocky. If your camera has a setting to save images as tiff, you can then convert the pictures to jpeg to get better compression ratios. You can use LZW compression (lossless compression) in tiff files if you want the file size to be smaller. Though consumer digital cameras can not handle multiple shots at once when it saving pictures as tiff because both the hardware in the camera and the flash medium can not keep up.

apokryphos · 09-06-2004, 01:08 PM

Tinkster, sorry to bother you again, but I'm having problems. Although I really don't know what to do with the bash script ;-), it seems to me as though the settings in there are quite different -- a png with something about 16x16.

I might appear lazy, but I'm really trying to just get this working. I got together with my brother and we managed to make a C++ program to do the job, but it has a few problems, and I'd much rather have it running from a simple "convert".

So, I guess, what I'm looking for is somewhere/thing to get knowledge on bash scripts from; for the moment, just enough to be able to make this thing work. Sorry for the hassle. Any help would be greatly appreciated.

Electro, thanks for the advice, I'll try to check my camera on that later. Though, it's not that good a camera. Don't get me wrong, it does the job, but I just doubt it'll have advanced functions like that. Thanks, anyhow.

Tinkster · 09-06-2004, 02:12 PM

Not a bother at all ... :)

The Linux Documentation Project :)

There's two guides to bash there.

http://www.tldp.org/LDP/Bash-Beginne...tml/index.html

http://www.tldp.org/LDP/abs/html/index.html

As for the 16x16, that's just the NAME, not
the format. You can easily change that, too.

And since you want to make jpg into smaller
jpg you could modify the script like this, making
every jpg it finds 50% smaller along each axis.

Code:

#!/bin/bash

# Pass the dir to look in as the first argument

for file in `find $1 -iname *.jpg`; do
convert -resize 50x50% $file $file
done

In fact, since we're not renaming it or anything
we can get away with a 1-liner quite easily :)

find -iname "*.jpg" -exec convert -resize 50x50% {} {} \;

which will modify all JPGs under the current directory.
Use with extreme caution ;}

Cheers,
Tink

apokryphos · 09-06-2004, 03:10 PM

I'm on a real low wavelength here, sorry.

When we make a bash script, I see we just run it, and it delivers a number of commands. Now I felt stupid for not guessing that. :P

Anyhow, I tried using that command that you suggested, but I had the same problem that I originally had -- not knowing how to use the -exec. The man page was a little useful, but didn't help that much.

When I type out your command in a terminal, I get this returned:
find: missing argument to `-exec'

I don't have to modify the command you suggested in any way, do I? Sorry, I promise to get it soon.

Tinkster · 09-06-2004, 03:19 PM

Code:

find -iname "*.jpg" -exec convert -resize 50x50% {} {} \;

Copy and paste that line into a terminal window...

You'll get the error message about the missing
argument if you omit the terminating \;

Cheers,
Tink

apokryphos · 09-06-2004, 03:43 PM

Ack, you're right. Terribly sorry. Thank you very much.

Tinkster · 09-06-2004, 04:13 PM

Soooo ... how about my affero? ;)

Cheers,
Tink

Electro · 09-06-2004, 04:17 PM

In david_ross script it has little bug. If your jpeg files has spaces in their paths, it will not work. Change the script from

Code:

#!/bin/bash

# Pass the dir to look in as the first argument

for file in `find $1 -name *.png`; do
name=`echo $file | sed 's/\.png/_16x16\.xpm/'`
convert $file $name
done

to

Code:

#!/bin/bash

# Pass the dir to look in as the first argument

for file in `find $1 -name *.png`; do
name="`echo "$file" | sed 's/\.png/_16x16\.xpm/'`"
convert "$file" "$name"
done

The double quotes (") preserves the spaces and tabs. After you create the script, you will have to use chmod to make the file executable or just the command sh follow by the name of the script that you want to run.