Episode: 4184
Title: HPR4184: Use GKRellM, wget and ImageMagick for a live slideshow
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr4184/hpr4184.mp3
Transcribed: 2025-10-25 20:57:58

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This is Hacker Public Radio Episode 4184 for Thursday the 15th of August 2024.
Today's show is entitled, Use Chrome, Get and Image Magic for a Live Slide Show.
It is hosted by GemLog and is about 10 minutes long.
It carries a clean flag.
The summary is, Chrome can show live from nails.
This script gets fresh data and types text on the images.
Hi, this is GemLog again in Canada, near Alaska.
This segment is about Image Magic and the GK Relum System Monitor and Highway Camps.
I'm pretty sure I'll have to do another segment about Image Magic the way I use it, maybe
you want an FFN Peg too, but that's FFN Peg is so huge, but so is Image Magic really.
The reason I use GK Relum as a system monitor is because computers are a lot like working
with electricity and wiring houses or doing board repairs or whatever, electricity is invisible
so you need things like meters and all scopes and stuff to tell you what's going on.
And with a PC, when things slow down, I might want to know what's happening.
It's the internet busy, my uploading, my downloading, what's the CPU doing, what's my
hard drive doing, what's the other hard drive doing, all that kind of gets stuck and what's
hogging the CPU, so that's why GK Relum is there.
And I just learned because I looked up GK Relum on Wikipedia, I'll just read you how
it's described, G and U Crel monitors, GK Relum is a system monitor software based on
the GK tool kit that creates a single process stack of system monitors, which is a whole
bunch of little boxes that stack up on top of one another on the study monitor.
It can be used to monitor the status of CPUs, main memory, hard disk, network interfaces,
local and remote mailboxes and other stuff.
In my case, I wanted it to look at webcamps as a slideshow one after another, so grabbing
them in real time, and I saw a plugin that would do that, and so I installed it like
you do, and it wouldn't work.
As I watched how it was trying to work, it would launch WGET to get the image, and then
it would just hang waiting for WGET to return, nothing would ever happen.
I nested it over and over again, it was a massive waste of time, well, for a geek waste
of time, it was probably like 20 minutes, I mean, mucking about.
But while I was doing that, I noticed that whatever test image I put on the disk, if
that was one of the hardwired, you know, direct reference files, it would change almost
right away, it was monitoring that file.
And so I wrote a bash grip like you do, to WGET those images from what in my case is my
provincial government, BC, British Columbia, Canada, for the highway cams, and I grabbed
it, you know, half a dozen, six or eight, I forget this now, highway cams, and those
appeared as thumbnails on the top of GK realm.
So I got the effect that I wanted, and it's pretty cool.
But then night time was a problem, because I couldn't always tell just where along the
Schiener River, a particular image was taken, because it was too dark for me to figure
it out, and the text was all too tiny in the thumbnail for me to see.
Now I could click on the thumbnail, and it would open up in image magic's display, I
think it does.
But as a glance, that's no good.
I mean, I can't read micro-pitch print, my eyes aren't that great to begin with.
And so I turned to image magic to fix the problem, so I just add to my WGET script that's
grabbing images anyway, and once the image has come in, I'll put some large text on them.
It should probably tell you what image magic is, just in case you don't know, but it's
a free open source software that's available for Linux and VSD, and probably other things,
MacOS and Microsoft maybe.
And pretty much everything you can do in the GIMP, you can do with image magic on a command
line.
But the tricky bit is, I've been cargo-culting image magic for decades now, because there's
so much to it, and it can be a little bit tricky to use, because of all the escaping and
fun quoting that you might have to do to make bash happy with it.
But you know, it's worth the trouble, and eventually you'll get there.
And so what I ended up doing, and then I'll put this in the show notes, was a fairly short
script.
Let me just bring it up here so I can talk about it, oh very short.
It's only 35 lines, and several of those are comments.
So all I did was, I made an array with the camera numbers, because that's how my provincial
DOT website works.
The URLs had camera numbers in them, so, and I just noticed now I didn't have to
declare the array, I just started using it.
That's lucky.
So anyway, in bash, apparently you don't have to declare an array before you use it.
So I just stuffed up this array with one, eight different camera numbers, and then I did
a wild-do with an embedded four, to just step through them and show them for a period
of time.
And every time it grabbed one, it used image magic to put in quite large text, and looks
like turquoise, which shows up very well in daytime and night time on the images, the location
of the camera in English, rather than, you know, camera 491 means nothing.
I went back to an old, old habit I have from Amiga days, which will give you a clue as
to how old I am, where I didn't have a graphical toolkit, and I was writing an accounting program,
and I wanted to make buttons, and so I learned to first stamp down the image of a button
in white to the upper left, and the same image in black to the lower right, and then finally
the same image in whatever color I really wanted the button to be on top of that in the middle,
and that provides like a 3D effect of the light shining from, in that case the upper left,
and then you can just reverse that to make a button and maybe gray out the color part
for when it's depressed. So I just did the same thing for this, I took the place name like
Rosswood or Hazleton, and stamp that down once in white, then once in black, and then finally
in turquoise on top in the middle of it, and that came up very well. The tools that come with
image magic are all separate, they're not in one big gooey like the Gimp, so you have
display, which will do what it sounds like, put up a little window, and show you something,
and you have in my case for this script what I used was convert and modify, and they both do
just the same thing except convert, the convert command operates on a copy, so you'll have to give it
the source file name, the source picture name, and then the target name
as an output, whereas magrify operates on the original, so you just give it the original name,
and it works with that. I think it came out quite well, I'm not sure, as I'm recording this,
how I'm going to show you what the result is other than just giving you that, maybe I can
well I can certainly put it on one of my websites, but maybe I could convince archive work to
take something I'm not sure, but I'm pretty sure you get the idea by now. So I hope that was helpful,
and you'll be able to do a couple of projects with that.
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