Continuing https://unix.stackexchange.com/questions/795046/how-to-automatically-straighten-a-scanned-document-in-debian-linux , how to automatically vertically un-shear a scanned page? Sometimes a combination of an imprecise printing and an imprecise scanning results in the following layout of the text lines in the resulting image: You see a vertical shear here. All the text lines go down here; we sometimes see also all the text lines going up. (For privacy reasons, I can't share a real scan here. An artificially created shear can be found in https://ibb.co/DHYWrGYT – it's a shear of page 6 of *The TeXbook* by Donald Erwin Knuth, 2020.) Out of an image with the above text layout, we'd like to create an image with text lines going horizontally: The un-shearing has to be done with freely available tools in Debian Linux with the least manual effort; ideally, this would boil down to calling a command that would determine the slope automatically, say, vertical_shear_fixer scan.png vertically_unsheared_scan.png. In this question, we assume for simplicity that all the text lines start at the same X value, i.e., that the original scan is not rotated and not horizontally sheared. (Rotating the original scan wouldn't solve the issue: for example, for the image above, rotating counterclockwise could somewhat straighten each text line (or black line) by itself but would introduce a horizontal shear, where the top text lines start more to the left than the bottom text lines; moreover, each letter could look tilted left a tiny bit.) We could start with gray images if it simplifies the matter.

Consider the image (the sensitive header and footer have been blanked for the purpose of this question, which would be valid also with them). As you see, it's a bit tilted clockwise. We tried to straighten it via

$ pngtopam test.png > test.pgm
$ rm -f test_unpaper.pgm && dpi=600 && unpaper -start 1 -end 1 --dpi $dpi -dr 10 -dp 0.01 -dv 10 -v test.pgm test_unpaper.pgm
…
detected rotation left: [235,0,4795,7015]: 0.000000
detected rotation right: [235,0,4795,7015]: 0.000000
rotation average: 0.000000  deviation: 0.000000  rotation-scan-deviation (maximum): 0.174533  [235,0,4795,7015]
rotate (2550,3508): 0.000000
…

We tried to play with the switches -dr and -dp; without them, the result is equally bad: the output is tilted in any case. Any improvement? Ideally, we'd like to get a straightened image automatically, without caring about switches; in particular, the effort should be less than for a precise manual rotation in GIMP. (An aside: for the purpose of this question, nothing else is needed: no denoising, no sharpening, no margin removal or image centering, ….).

I'm comparing 2 images using imagemagic (compare a.png b.png -compose src diff.png): They don't look much different at all. Yet the diff image from imagemagick-compare is so hard to read: How can I just visualize simply the abs(pixel_a - pixel_b) of 2 images without introducing those postprocessing and rescaling effect? I imagine for this specific case the diff image should be mostly dark with a few grey points.

This is a pretty straightforward question. I am writing a Qt program that looks to render graphics in the terminal. To do that, I utilize Sixel Graphics which has a large overhead. I would rather render directly to the frame buffer, but can that be done while X and Wayland are running? Or do I have to strictly be in a headless environment, meaning no active desktop environment, to be able to access this? Does X or Wayland perhaps have functions allowing me to use it to render graphics through it? Thanks.

I've a docker container running on my Linux host. root@eve-ng-6:~# docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES ea25d3afa65d ios-xr/xrd-control-plane:latest "/usr/sbin/init" 2 hours ago Up 2 hours 3e2241f3-f914-456a-891f-671c42fafef3-0-5 root@eve-ng-6:~# root@eve-ng-6:~# systemctl status docker.service ● docker.service - Docker Application Container Engine Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled) Drop-In: /etc/systemd/system/docker.service.d └─http-proxy.conf, tcp-sock.conf Active: active (running) since Thu 2025-05-29 13:12:13 UTC; 3min 54s ago TriggeredBy: ● docker.socket Docs: https://docs.docker.com Main PID: 1265607 (dockerd) Tasks: 19 Memory: 38.5M CPU: 1.258s CGroup: /system.slice/docker.service └─1265607 /usr/bin/dockerd -H fd:// -H tcp://127.0.0.1:4243 root@eve-ng-6:~# ps -ef | grep 1265607 root 1265607 1 0 13:12 ? 00:00:00 /usr/bin/dockerd -H fd:// -H tcp://127.0.0.1:4243 root 1271097 674199 0 13:16 pts/3 00:00:00 grep --color=auto 1265607 root@eve-ng-6:~# Is there a way to connect to its primary process using an URL like docker://127.0.0.1:4243/ ? Thanks. Edit: based on comment received, I'd ask whether it is possible to redirect stdin/stdout of docker attach command to a tcp socket. Searching for it I found docker attach > You can't redirect the standard input of a docker attach command while > attaching to a TTY-enabled container (using the -i and -t options). Does this mean that it is actually not feasible to do that ?

I can successfully display images using the following command: sudo fbi -T 1 /home/pi/photo-screen/photos/*.jpg -t 4 I now want to start a slide show of those pictures as soon as the Raspberry PI boots up. So I added a systemd file like so:

`service
[Unit]
Wants=graphical.target
After=graphical.target

[Service]
Type=simple
User=pi
Group=pi
WorkingDirectory=/home/pi/photo-screen
ExecStart=sudo bash -c "fbi -T 1 -d /dev/fb0 photos/*"
Restart=always
RestartSec=20

[Install]
WantedBy=multi-user.target

`

● photo-screen.service
     Loaded: loaded (/etc/systemd/system/photo-screen.service; enabled; vendor preset: enabled)
     Active: active (running) since Mon 2023-12-11 15:12:07 CET; 61ms ago
   Main PID: 1080 (sudo)
      Tasks: 2 (limit: 472)
        CPU: 23ms
     CGroup: /system.slice/photo-screen.service
             ├─1080 sudo bash -c fbi -T 1 -d /dev/fb0 photos/*
             └─1082 fbi -T 1 -d /dev/fb0 photos/0058966c-7ee5-4fc0-80ec-55885809567b.jpg photos/04669eb7-bf5e-4cbf-ab8f-fc7b3566186d.jpg photos/0cc1ad40-1b05-4f1c-beae-0c285d6b62>

Dec 11 15:12:07 foto systemd: Started photo-screen.service.
Dec 11 15:12:07 foto sudo:       pi : PWD=/home/pi/photo-screen ; USER=root ; COMMAND=/usr/bin/bash -c fbi -T 1 -d /dev/fb0 photos/*
Dec 11 15:12:07 foto sudo: pam_unix(sudo:session): session opened for user root(uid=0) by (uid=1000)

Please note that I am signed in via SSH so assigning the right tty does work fine with the -T 1 parameter. I tried: - Including chvt 1; in my script - Running it as root - Adding the option -d /dev/fb0 to my script - Using fim but there I have the exact same problem - Using non-relative paths I have a screen attached and the login prompt does at some point get black but I don't see any images. I did get OOPS Terminated at some point on the screen above the login prompt. Also when I fill the screen with random stuff then it will be overwritten after some time with a black bar that fills around 80% of the screen: cat /dev/random > /dev/fb0 I tried replacing my fbi-script with cat /dev/random > /dev/fb0 but that did not fill the screen either. I thought that giving an elevated bash terminal might fix the problem: sudo bash -c "chvt 1; fbi -T 1 -d /dev/fb0 images/*" That again works via my ssh terminal but not using systemd.

I can view a pdf image with text using the evince document viewer, however I cannot select the text in the image to copy and paste. How do I copy text from an image in a pdf file?

I mean, how to generate images files from a video like screenshots.

I'm trying to find the most lightweight method to detect "adequate" change in an image. I realize that's a terrible constraint, so for the sake of this question I'll break it into two different qualifiers: substantial change, or 80% pixels changed, and motion-changed, or 10% pixels changed. These images are captured via timelapse mode on a raspberry pi camera, but for the sake of the question, _the files could be from any basically-static view point_. I've found that I can use filesize to observe change of substantial amounts:

user@host-bb:/tmp$ ls -la investigating/
total 134604
drwxr-xr-x 2 user group    4096 Oct 20 00:05 .
drwxr-xr-x 5 user group    4096 Oct 20 00:04 ..
-rw-r--r-- 1 user group 4580181 Oct 20 00:05 image1018223300.jpg
-rw-r--r-- 1 user group 4573449 Oct 20 00:05 image1018223301.jpg
-rw-r--r-- 1 user group 4573024 Oct 20 00:05 image1018223304.jpg
...snip...
-rw-r--r-- 1 user group 4455867 Oct 20 00:05 image1018223320.jpg
-rw-r--r-- 1 user group 4447607 Oct 20 00:05 image1018223321.jpg
-rw-r--r-- 1 user group 4434839 Oct 20 00:05 image1018223323.jpg
-rw-r--r-- 1 user group 4416942 Oct 20 00:05 image1018223324.jpg
-rw-r--r-- 1 user group 1769008 Oct 20 00:05 image1018223325.jpg
-rw-r--r-- 1 user group 1702851 Oct 20 00:05 image1018223326.jpg
-rw-r--r-- 1 user group 1639306 Oct 20 00:05 image1018223327.jpg
-rw-r--r-- 1 user group 1788435 Oct 20 00:05 image1018223328.jpg
-rw-r--r-- 1 user group 1908061 Oct 20 00:05 image1018223329.jpg
-rw-r--r-- 1 user group 1981029 Oct 20 00:05 image1018223330.jpg
-rw-r--r-- 1 user group 2102390 Oct 20 00:05 image1018223331.jpg
-rw-r--r-- 1 user group 2167734 Oct 20 00:05 image1018223333.jpg
-rw-r--r-- 1 user group 2243082 Oct 20 00:05 image1018223334.jpg
...snip...
-rw-r--r-- 1 user group 2640732 Oct 20 00:05 image1018223342.jpg
-rw-r--r-- 1 user group 2730206 Oct 20 00:05 image1018223343.jpg
-rw-r--r-- 1 user group 2751966 Oct 20 00:05 image1018223344.jpg
-rw-r--r-- 1 user group  315875 Oct 20 00:05 image1018223345.jpg
-rw-r--r-- 1 user group  302476 Oct 20 00:05 image1018223352.jpg
...snip...
-rw-r--r-- 1 user group  285965 Oct 20 00:05 image1018223358.jpg
-rw-r--r-- 1 user group  289271 Oct 20 00:05 image1018223359.jpg
user@host-bb:/tmp$

Even between somewhat non-major changes in lighting (such as occurred between images *28.jpg and *29.jpg) can produce a difference in filesize. I realize this is basically binning, and it could be the solution I'm looking for. This takes care of the "substantial change" (80% of pixels changed). The question remains though: Short of Imagemagick, Python script, or other image processing software, is there a lightweight way to detect change in an image that is closer to 10% pixels changed? If there is no non-image-processing software option, what would the most light-weight option be? Writing my own processing in a low-level language? A Python script? I'm coming from a Python background and am trying to do simple change detection on a raspberry pi zero w that can then trigger an event (file upload) if there is a change. Bandwidth is too small to send all the images, and the pi zero w is not a heavy hitter when it comes to processing power.

I have checked that a lot of images in a website are completely blank, ie, 500x500 with all pixels white. All the images are in subdirectories of the images directory. How can I check which ones are white? I am thinking on getting the names of these images. **UPDATE**: - I would like to use some bash script or command. - Imagemagick is installed - Server is Ubuntu 14.04 - All images are .jpg extension

I want to find screenshot files, having a specific pixel height of 2220 and width of 1080, and want to move them into another folder. That's nothing I can do manually, as the source is 100+k images or so. I've found the following command, but not able to bring it to work: find /Users/myuser/Desktop/daten/JPG -name "*.jpg" -exec bash -c "sips -g pixelHeight -g pixelWidth {} | grep -E '2220‘ >/dev/null" \; -exec mv {} /Users/myuser/Desktop/screenshots \; Error message: bash: -c: line 0: unexpected EOF while looking for matching `'' bash: -c: line 1: syntax error: unexpected end of file Thank you for your help. UPDATE: fixed the command and removed the blank in the folder name to: find /Users/myuser/Desktop/daten/JPG8 -name "*.jpg" -exec bash -c "sips -g pixelHeight -g pixelWidth {} | grep '2220' >/dev/null" \; -exec mv {} /Users/myuser/Desktop/screenshots \; .. but still not working well - no files have been moved.

I have a directory with a large list of image files (JPG). Some of them have a specific rating, which is recorded as XMP data . An example would be > XMP Exif > xmp:Rating = 5 (for a file that has 5 stars). I would like to select all files in bash that have a certain rating, and then move/copy them to a specific directory. I have found some roundabout ways using e.g. Python or PHP but am wondering if there could be a more straightforward way?

I have ppm file X.ppm with comment : xxd X.ppm|head -10 0000000: 5036 0a23 206d 6967 6874 796d 616e 6465 P6.# mightymande 0000010: 6c20 2d32 2e38 3034 3132 3232 3037 3833 l -2.80412220783 0000020: 3834 3132 3833 3535 3139 3235 652d 3032 841283551925e-02 0000030: 202b 2036 2e39 3438 3932 3238 3438 3134 + 6.94892284814 0000040: 3730 3430 3430 3831 3238 3631 652d 3031 704040812861e-01 0000050: 2069 2040 2034 2e34 3430 3839 3230 3938 i @ 4.440892098 0000060: 3530 3036 3237 3165 2d31 360a 3132 3830 5006271e-16.1280 0000070: 2037 3230 0a32 3535 0aff ffff ffff ffff 720.255........ 0000080: ffff ffff ffff ffff ffff ffff ffff fefe ................ 0000090: fefc fcfc f8f8 f8e8 e8e8 4141 4140 4040 ..........AAA@@@ It is created with c code : void record_write(FILE *out, unsigned char *buffer, int width, int height, mpfr_t centerx, mpfr_t centery, mpfr_t radius) { fprintf(out, "P6\n"); mpfr_fprintf(out, "# mightymandel %Re + %Re i @ %Re\n", centerx, centery, radius); fprintf(out, "%d %d\n255\n", width, height); fflush(out); for (int y = height - 1; y >= 0; --y) { fwrite(buffer + y * width * 3, width * 3, 1, out); } fflush(out); } I can convert it to png : xxd X.png|head -10 0000000: 8950 4e47 0d0a 1a0a 0000 000d 4948 4452 .PNG........IHDR 0000010: 0000 0500 0000 02d0 0802 0000 0137 187a .............7.z 0000020: 9700 0000 5f74 4558 7454 6974 6c65 002d ...._tEXtTitle.- 0000030: 322e 3830 3431 3232 3230 3738 3338 3431 2.80412220783841 0000040: 3238 3335 3531 3932 3565 2d30 3220 2b20 283551925e-02 + 0000050: 362e 3934 3839 3232 3834 3831 3437 3034 6.94892284814704 0000060: 3034 3038 3132 3836 3165 2d30 3120 6920 040812861e-01 i 0000070: 4020 342e 3434 3038 3932 3039 3835 3030 @ 4.440892098500 0000080: 3632 3731 652d 3136 aba5 7721 0000 0015 6271e-16..w!.... 0000090: 7445 5874 536f 6674 7761 7265 006d 6967 tEXtSoftware.mig It also contain comment, but : - It is not exif ( and ppm is not supported by eviv2 library ). - Gimp also do not show comment from ppm or png file ( why ?) - identify -verbose X.ppm shows comment What program should I use to extract comment from ppm files ?

**EDIT!** so i guess it's not a matter of colour profiles or operating systems, but of whatever program linux uses to render images by default..? maybe??? because when i open up the same image in both image viewer (left, incorrect colour perception) and imagemagick (right, correct colour perception), i get the same results as i do when i open it between firefox on linux and windows.  so i'm guessing now that i have to change the way linux renders images by default, if there's even a way to do that. it's not SUPER important, since i now know there's a program that can display my art correctly, but it would be nice. **OG POST** i've been gradually settling myself into mint the last few days, since i wanna start inching myself away from windows and all the crap it's pulling. i've mostly been able to figure out everything on my own, but one thing is tripping me up; the way that mint (or maybe ubuntu as a whole?) renders the colours of images is off. i'm a digital artist. colour accuracy is something i really need to have. none of the usual colour profiling tools worked for me (gnome colour manager doesn't have the functionality i need, and every other effective tool needs an expensive piece of hardware that you stick to the screen) so i then decided to boot up my windows VM and take a look at the same website, side by side. the colours come through differently!! top is how it's rendering in linux mint with firefox (incorrect, banner image colour does not match nav elements), bottom is how it's rendering in windows 11 pro with firefox (correct colours).  i checked the same image in clip studio paint (which i got running through playonlinux), and it's rendering the picture the same as it is in the windows VM. so while i at least don't have to worry about linux messing up my art WHILE i'm making it (and hopefully when i'm making breakpoints as well), this is still probably something that's gonna bug me... anyone got tips for fixes, or do i just have to deal with it? running linux mint 22.1 cinnamon 6.4.7 with the X11 display server. let me know if there's anything else i should include for you nerds, since i'm still pretty new at this whole linux thing.

Cross posted from linux mint forum, where no response was received. My workflow involves having multiple images open and simultaneously visible and editable, in a single frame, in a single instance of the application. This allows me to paste back and forth between images, without having to (in effect) make the image in a tab visible. My workflow also involves being able to copy an on-focus image, and then paste it into a new image "automatically" (again in the same frame), where I don't have to first create the new canvas. This functionality is provided by Paint Shop pro 5, which I have been using under wine in Mint 20. I would very much like to ditch Paint Shop Pro it in favor of a native linux app, that offers this specific functionality. I have explored the following apps somewhat superficially - to the best of my knowledge, none of them will do what I want: pinta, gwenview, nomacs, digikam, image magick, gtthumb, krita, gphoto, showfoto. I also briefly attempted to explore gimp plug-ins; again no joy. Please let me know if you know of a native linux app or gimp plugin that replicates this particular Paint Shop Pro functionality. For what it's worth, prior to posting this question, I searched this forum and others for questions directly on point with respect to this particular functionality, and didn't find anything. Given the situation, and given that Corel Draw (the makers of Paint Shop Pro) services the Apple and Windows operating systems but not linux, I am beginning to suspect that I am beating a dead horse. That is, there may be something inherent in the Linux "windowing" system that makes this functionality problematic. I also welcome any technical opinions, re the previous paragraph. Further, if you think that I am beating a dead horse, I welcome any suggested app, that you think "comes closest" to what I want.

Is there any image viewer (like eog) for linux which can do the following: Show 2 (3 or 4) images of a directory with maximal possible sizes on one page at the same time. When I click "next", it should show me the next 2 (3 or 4) images of that directory and so on.

I have a bunch of MP3 files that have their album art included within the file itself. I am now looking for a way to extract them to store them separably, at best from command line. Is there a way to achieve this?

My preferred image viewer is Feh. When I open a small image with Feh, there is very intrusive interpolation between pixels. I would like to turn this off and just view the raw pixels. How can I do this with Feh? Or will another program be in order? Edit: I realise the original post was ambiguous. My question is better stated as "how can I view the image zoomed in with an interpolation which preserves the original blockiness?"; e.g., zooming x and y by 2 should render a single blue pixel as a 4-pixel large blue block. This intention was inferred from my OP and I have accepted an answer :)

I wanted to use libreoffice draw to draw network diagrams. I searched a little and found out that there is an extension called VRT ( https://extensions.libreoffice.org/en/extensions/show/vrt-network-equipment ) Also I've heard that Libreoffice Draw should be able to use the cisco eps icons if I convert them to svg ( https://www.peteredstrom.se/how-to-import-cisco-network-symbols-in-libreoffice-draw ). I was wondering what you could suggest me to use if you used different themes/icons.

I have some arbitrarily-sized images for which I want to produce fixed-size 800x600 thumbnails, which keep the original image ratio and add white letterboxing to make up the rest of the space. I'd like the letterboxing to be as minimal as possible, which means that the process would do the following: - choose whichever axis is largest - if x is largest, scale the image (keeping the ratio) so that new x is 800. - if y is largest, scale the image (keeping the ratio) so that new y is 600. - the result, at this point, will not be 800x600 (unless the original happened to be exactly 4:3 ratio), so centre the result in an 800x600 rectangle and add a white background. I can do the first 3 steps with convert -resize 800x600 $input $output so I suppose I could overlay that on top of another image using some other imagemagick tool, but it would be great if I could do it in one hit. Anyone know if this is possible?