Using built-in imagemagick to crop an image

[nasser]

How do I use the built-in imagemagick application to crop an existing image in .png format?

- the image is generated by the "press opposite corners" screenshot trick.
- I use pw1 and pw3. So the images would be 758x1024 and 1072x1440.
- I assume the IM command can be entered from kterm and could be converted into a KUAL extension.. since the crop size and location I want is fixed
- I want to generate a screenshot from the Eboard Chess application and do a crop so that I get an image of the board only.

[knc1]

man imagemagick

Either on a full *nix installation (one with the man(ual)s intalled) or in your web search engine.

[nasser]

Hmm... I was asking about using imagemagick ON the Kindles..
I read here somewhere that the screensavers hack uses it.

[knc1]

Originally Posted by nasser

Hmm... I was asking about using imagemagick ON the Kindles..
I read here somewhere that the screensavers hack uses it.

It is only the man command that does not work on the Kindle.
I.E:
The Linux (a *nix system type) is not a full installation, it is only a partial, embedded system.
So you need to have access to either a complete install of a *nix based system or access to a web search engine (both will recognize the manual command I listed for you).

IM is not pre-installed that I know of, it is part of the ss package.

[Yourcat]

IM should support the basic features, also on Kindle. Did you try 'convert -crop ...' already?

[nasser]

I tried convert command without any arguments on my pw3 and I got a help list. But on my pw1 I got a 'command not found' message. How come? I have installed the screensaver hack on my pw1. Isn't it supposed to be using IM?

[knc1]

Start checking with the most basic possiblities -
Is the PATH variable the same on both devices?
On the one that is found, where is it?
Check the same path on the one that is not found, is it really not there?

[nasser]

Thanks, knc1!
I already checked.

On both the pw1 and pw3, there is a "convert" executable in the '/mnt/us/linkss/bin' folder. However this executable is not in the PATH variable.

On the pw3, there is an additional "convert" executable in the '/usr/local/bin' folder - which is in the path variable.

So, that clears up the mystery!

Also, '/usr/local/bin' of the pw3 contains lots of other stuff. These are the goodies you mentioned would be available in the "factory" image, which gets stripped out in the "customer" image, like in my pw1 - which only contains "usbnetwork.sh".

You had also mentioned the possibility of transferring these goodies over to a "customer" image kindle. Would a plain copy work?

Ok. Let me play with 'convert' now..

[knc1]

Better to make an archive of it and copy the archive:

cd /usr
tar -czf /mnt/us/factutil.tgz local

Then move the archive from the top level of visible USB storage to top level of visible USB storage on the other device.

cd /usr
tar -xzf /mnt/us/factutil.tgz

That way ownerships and permissions are preserved, which would not be if you just copied the files to FAT-32 and then back again.

[nasser]

Success!
Got what I wanted..

Steps:

1. Install screensavers hack, if not already installed.
2. In Eboard Chess settings, untick the "Show Coordinates" option.
3. Play through a game, or set up a position using the scratch board option.
4. Touch opposite corners to capture the screen image. This will be saved in /mnt/us as "screenshot_2016..png".
5. Make some more positions and screenshot them, as required.
6. Create /mnt/us/images folder, if it doesn't exist already.
7. Open kindle explorer and rename the screenshots to something more convenient, as required.
8. Open kterm. Navigate to folder /mnt/us(this can be done directly in kindle explorer by touching the kterm icon).
9. Run command

   for n in *.png; do /mnt/us/linkss/bin/convert $n -crop 617x617+2+39 /mnt/us/images/$n; done

   This crops the screenshots and saves them under the same names in the /mnt/us/images folder. Note that the crop parameters are for a 212 ppi PW1. For 167ppi and 300ppi resolution kindles, the crop sizes and offsets will be different.

Sample before/after images attached.

Thanks to all for help!

[Yourcat]

Typo in 6 & 9: '/mnt/images folder' instead of '/mnt/us/images folder'.

[knc1]

Ah, so.
Now you are ready to write a chess, e-book with illustrations your certain will display on a Kindle, since they came from a Kindle.

Shown:
Common Openings: Ruy Lopez, a.k.a: Spanish Opening.

[nasser]

Thanks, Yourcat!
/mnt/us/images it is. Corrected.

Yes, knc1!
That's one of my future projects. For now, light duty kindle hacking is enough fun...