Archive for Internet
gnome-keyring you won’t get a useful error message. If you uninstall it, you’ll get the real culprit right where it matters, but in retrospect
ssh-add gives you the same error message:
$ git pull upstream master @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: UNPROTECTED PRIVATE KEY FILE! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ Permissions 0644 for '/home/frans/.ssh/id_rsa' are too open. It is required that your private key files are NOT accessible by others. This private key will be ignored. Load key "/home/frans/.ssh/id_rsa": bad permissions firstname.lastname@example.org: Permission denied (publickey). fatal: Could not read from remote repository. Please make sure you have the correct access rights and the repository exists.
That means something like this, or maybe just read:
So much for the GitHub help. 🙂
Facebook’s OpenGraph and Twitter Cards are mostly an annoying duplication of standardized metadata (more details here). Moreover, you can just leave out the nonsense because it will fall back on regular meta description. Always good to know.
Anyway, the main and perhaps only redeeming feature here is that they allow you to specify images to display. That’s cool. It makes your posts stand out better. Here’s how that looks for my snarky post about WordPress trying to sell me some nonsense about Firefox 52:
But then I innocently tried to use an SVG image for a post.
Provided og:image URL, https://fransdejonge.com/wp-content/uploads/2018/02/android-planet-logo-openclipart-web.svg does not have a supported extension.
It’s 2018 and this is a thing. You’ll either have to manually add a PNG or JEPG or do it programmatically. Grmbl.
about:config, as ever. Then disable
Most people seem to have switched to statically generated blogs like Hugo by now, but I’ve been using WordPress for some 13 years and combined with WP-Super-Cache it’s been static for pretty much that entire time. There’s little point to putting in extra time and effort just for some extra nerd cred.
On the downside, every new 4.0+ release seems to add more cruft to the header. My
functions.php consists of an ever-growing list of
remove_action incantations. Here’s the latest addition, necessitated by WordPress 4.9.
// remove WP 4.9+ dns-prefetch nonsense remove_action( 'wp_head', 'wp_resource_hints', 2 );
For those interested, here’s my full messy collection, including a few hints I commented out.
When I logged in, WordPress tried to inform me that the particular browser I was using was out of date.
So, is it?
Well, we can take a look at the Firefox ESR download page to find out.
Nope. Still Firefox 52, which will remain supported until Firefox 60.
Always fun, these automated checks. 🙂
On the forum I administer, I am forced to run a tight attachment policy. Disk space doesn’t grow on trees. Occasionally this leads to questions about the small attachment size limit of 50 KiB. This guide is intended to clarify that this is not nearly as tiny as you might think. Note that although I’ll mention commands without much explanation for the sake of brevity, you’re always recommended to further explore the possibilities offered by those commands with the
--help flag as well as by running
First you need to ask yourself what kind of file type is appropriate, if you have the choice. On screenshots, the main purpose of attachments on my forum, you’ll often encounter large areas of uniform background colors. PNG is therefore almost invariably the right choice. Crop out everything but what’s relevant. JPEG is appropriate for more dynamic pictures such as photographs. If you want to do a lot with photographs, you might want to consider an external hosting service. My wife likes SmugMug. Still, for thumbnails you might be able to do a fair bit more within a few hundred KiB than you might think. Finally, the vector graphics in SVG result in pictures that always look sharp. You’ll typically have drawn these in a program like Inkscape or Adobe Illustrator.
Table of Contents
- 1. Optimizing JPEG
- 2. Optimizing PNG
- 3. Optimizing SVG
- Addendum A: Scanned Documents
- Addendum B: Video
1. Optimizing JPEG
Often you’ll want to crop your file. Do not edit your JPEG followed by resaving it because this will result in reduced quality! You can crop losslessly with cropgui. On Windows you can use IrfanView.
If you don’t want to crop, and also potentially for some post-cropgui optimization, use
jpegtran -copy none -progressive -optimize file.jpg > file-opt.jpg. Note that this will get rid of all metadata, which may be undesirable. If so, use
jpegtran -copy all -progressive -optimize file.jpg > file-opt.jpg.
Of course if you want to scale down your JPEG there’s no point in mucking about with lossless cropping first. After scaling down, check how low your quality can go (also see a little helper script I wrote). In any case, you should avoid introducing any unnecessary compression steps with associated quality loss. Here are some results:
The original 11.jpg at 2.19 MB.
Losslessly cropped 11-crop.jpg at 1.11 MB.
-copy all -progressive -optimize11-crop-opt.jpg at 1.04 MB.
-copy nonewould’ve saved an extra whopping 40-some KiB, which on this kind of filesize has little benefit, and besides, I quite like the metadata. For thumbnail-sized files the balance is likely to be different. For example, the 52.2 KiB SmugMug auto-generated thumbnail below can be insignificantly reduced to 51.1 KiB with
--copy all, but to 48.2 KiB with
--copy none. I think an 8% reduction is not too shabby, plus it brings the file size down to under the arbitrary 50 KiB limit on my forum.
2. Optimizing PNG
As I wrote in the introduction, for screenshots PNG is typically the right choice. If you want to use lossless PNG, use
optipng -o7. In my experience it’s ever so slightly smaller than other solutions like
pngcrush. But as long as you use a PNG optimizer it shouldn’t much matter which one you fancy. Also see this comparison.
If you don’t care about potentially losing some color accuracy, use
pngquant instead. To top it off, if you really want to squeeze out your PNG, you can pass quality settings with
--quality min-max, meaning you can pass
--quality 30-50 or just
--quality 10. Here are some quick results for the screenshot in the SVG section below, but be sure to check out the pngquant website for some impressive examples.
$ du -h --apparent-size inkscape-plain-svg.png 27K inkscape-plain-svg.png $ du -h --apparent-size inkscape-plain-svg-fs8\ default.png 7.6K inkscape-plain-svg-fs8 default.png $ du -h --apparent-size inkscape-plain-svg-fs8\ quality\ 10.png 4.3K inkscape-plain-svg-fs8 quality 10.png
In this case there is no visual distinction between the original PNG and the default pngquant settings. The quality 10 result is almost imperceptibly worse unless you look closely, so I didn’t bother to include a sample.
3. Optimizing SVG
For using SVG on the web, I imagine I don’t have to tell you that in Inkscape, you should save your file as Plain SVG.
What you may not know is that just like there are lossy PNGs, you can also create what amounts to lossy SVGs. There are some command-line tools to optimize SVGs, including (partially thanks to this SO answer):
- Scour is probably the best command line tool for some quick optimization. You can just use the defaults like
scour < in.svg > out.svgor
scour -i in.svg -o out.svg. But I recommend you go further.
- SVGO (SVG Optimizer)
- SVG-optimiser (by Peter Collingridge)
- SVG-editor (by Peter Collingridge)
My personal preference for squeezing out every last byte goes toward the web-based version of the SVG-editor by Peter Collingridge. By running it in a browser with inferior SVG support such as Firefox, you’ll be sure that your optimized SVG still works properly afterward. The command line tools can only safely be used for basic optimizations, whereas the effects of going lossy (such as lowering precision) can only be fully appreciated graphically.
Addendum A: Scanned Documents
Scanned documents are a different item altogether. The best format for private use is DjVu, but for public sharing PDF is probably preferable. To achieve the best results, you should scan your documents in TIFF or PNG, followed by processing with unpaper or ScanTailor. If you’ve already got a PDF you’d like to improve, you can use pdfsandwich or my own readablepdf.
Addendum B: Video
I’m not aware of any lossless optimization for video compression such as offered by jpegtran, but you can often losslessly cut video. In the general purpose editor Avidemux, simply make sure both video and audio are set to copy. There is also a dedicated cross-platform app for lossless trimming of videos called, unsurprisingly, LosslessCut. If you do want to introduce loss for a smaller file size you can use the very same Avidemux with a different setting, ffmpeg, mpv, VLC, and so forth. You can get reasonable quality that’ll play many places with something like:
ffmpeg -i input-file.ext -c:v libx264 -crf 19 -preset slow -c:a libfaac -b:a 192k -ac 2 output-file.mp4
For the open WebM format, you can use something along these lines:
ffmpeg -i input.mp4 -c:v libvpx -b:v 1M -c:a libvorbis output.webm
More examples on the ffmpeg wiki. Note that in many cases you should just copy the audio using
-acodec copy, but of course that’s not always an option. Extra compression artifacts in audio detract significantly more from the experience than low-quality video.
Just so long as you don’t depend on it. In this case we’ve got Gmail’s automated translation feature, which I’ve probably only used once or twice in the past decade in order to see how it worked. Today it had the nice idea to suggest interference in English.
There is in fact French text hiding in the conversation history. Funny thing though — there’s no suggestion to translate on any of the preceding or following messages that are actually in French. So it goes.
QuiteRSS is a terrific piece of software. It only has one flaw, which is that it only runs on my desktop. Unfortunately this has led to me increasingly getting behind on the things I like to read. Sometimes this is fine, like when I can read a book instead, but other times it’s mildly frustrating.
It would seem that none of the online feeds readers, whether self-hosted or SaaS, support the paradigm I’m used to. They’re all following the “golden standard” of nightmarish, thankfully-it’s-gone Google Reader. Basically I use feeds like emails. Most I delete after reading. Those I want to keep for reference I keep around, marked read.
But not so with these feedreaders. Feeds you want to keep for later reading should preferably be favorited, bookmarked, or maybe saved to a system like Wallabag. This has advantages too, of course. By centralizing your to-read list in one location, like Wallabag or Pocket, you don’t have the problem of remembering what’s where, or that you have loads of unread open tabs in various browsers.
Long story short, after sampling a whole bunch of feedreaders I opted for FreshRSS. It suffers from the omnipresent “no pages” disease. Got a feed with a thousand items? (Yes, they exist.) You can go to the start or the beginning by sorting in ascending or descending order, but reading things somewhere down the middle? Forget it.
These minor inconveniences are worth it, however. This way I can easily read my feeds from any computer anywhere in the world. The feeds are always updated, provided you set up a cron job. I don’t have to start up my computer or risk missing anything if I’m on vacation for a few days. I can quickly check them on my cellphone during an otherwise wasted moment. Overall I’m happy. Goodbye, QuiteRSS. You were a good friend after Opera died, but it’s time to move on.
PS Here are some feed-related links that should go along nicely with any feed reader.
- Feed Creator allows you to create feeds for webpages that are missing them.
- So does RSS-Bridge, but since it’s self-hosted it fits perfectly next to FreshRSS in the kluit spirit.
- Tubes is a tool I wrote a few years back that can filter and fix up feeds. Useful if a website happens to have a feed, but not on a per-category basis or some such. Or of course because you might want to subscribe to an hourly news podcast, but only get the news once a day.
I was suddenly having trouble connecting to GitHub, after pulling in an OpenSSH update to version 7. Chances are that means the problem is security-related, meaning it’s worthwhile to take the time to investigate the cause.
$ git pull
Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
A little debugging showed the following:
$ ssh -vT email@example.com
OpenSSH_7.1p2 Debian-2, OpenSSL 1.0.2f 28 Jan 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to github.com [126.96.36.199] port 22.
debug1: Connection established.
debug1: Skipping ssh-dss key /home/frans/.ssh/id_dsa for not in PubkeyAcceptedKeyTypes
debug1: No more authentication methods to try.
Permission denied (publickey).
Of course I could quickly fix the problem by adding
PubkeyAcceptedKeyTypes ssh-dss to
~/.ssh/config, but checking OpenSSH.com tells me that “OpenSSH 7.0 and greater similarly disables the ssh-dss (DSA) public key algorithm. It too is weak and we recommend against its use.” So, although I could obviously re-enable it easily, I guess I’ll have to generate a new key. I hope GitHub’s guide is accurate for generating something sufficiently secure, because I’m kind of ticked off that something I generated in 2013 is already considered “legacy.” I hope I’m to blame and not an earlier version of GitHub’s guide.
Incidentally, to change the passphrase one would use the
-p option, e.g.:
ssh-keygen -f id_rsa -p