Images

File formats

Explaining Image File Formats (video)

Note we can compress files before we share them/upload to web servers.

Free images

https://unsplash.com/

StockAI

https://www.stockai.com/ Free AI-generated stock photos

Convert a color image to black and white/grayscale

• https://linux.cn/article-8851-1.html
• https://www.imagemagick.org/script/command-line-options.php#canny

$ convert filename.jpg -canny 0x1 -negate canny.jpg
convert.im6: unrecognized option `-canny' @ error/convert.c/ConvertImageCommand/1107.

$ convert filename.jpg +clone +level-colors gray,white -background black -alpha remove -colorspace Gray canny.jpg

$ convert filename.jpg -monochrome canny.jpg

$ convert filename.jpg -colorspace Gray canny.jpg  # Best

The current imagemagick version is 7.0.7-15.

GUI

Convert and Manipulate Images With ‘Converter’ GUI Tool in Linux

Free-to-Use Image-Editing Apps for Linux

The Top 9 Free-to-Use Image-Editing Apps for Linux

Install/build the latest imagemagick

• https://www.imagemagick.org/script/install-source.php
• https://gist.github.com/makenova/78bb63aaa1050e2ad8019ee1e7e7b433
• https://www.tutorialspoint.com/articles/how-to-install-imagemagick-on-ubuntu

# remove version installed with apt-get
sudo apt-get remove imagemagick && sudo apt-get autoremove

# install dependencies
sudo apt-get install build-essential
sudo apt-get build-dep imagemagick -y

# download ImageMagick source
wget http://www.imagemagick.org/download/ImageMagick.tar.gz
tar xzvf ImageMagick.tar.gz

# build source
cd ImageMagick-*
./configure
make

# install and verify
sudo make install
sudo ldconfig /usr/local/lib

sudo checkinstall

**********************************************************************

 Done. The new package has been installed and saved to

 /home/XXX/Downloads/ImageMagick-7.0.7-15/imagemagick-7.0.7_15-1_amd64.deb

 You can remove it from your system anytime using: 

      dpkg -r imagemagick-7.0.7

**********************************************************************

$ convert --version
# bash: /usr/bin/convert: No such file or directory

$ which convert
/usr/local/bin/convert
$ whereis convert
convert: /usr/local/bin/convert
$ /usr/local/bin/convert -version
Version: ImageMagick 7.0.7-15 Q16 x86_64 2017-12-20 http://www.imagemagick.org
Copyright: © 1999-2018 ImageMagick Studio LLC
License: http://www.imagemagick.org/script/license.php
Features: Cipher DPC HDRI OpenMP 
Delegates (built-in): bzlib fontconfig freetype jbig jng jpeg lzma pangocairo png tiff x xml zlib

Convert an image to sketch (online tool)

• http://www.snapstouch.com/sketch.aspx
• Fred's ImageMagick Scripts

convert my-image.jpg -colorspace Gray my-image-gray.jpg
# OR
convert <img_in> -set colorspace Gray -separate -average <img_out>

To convert into a 2-bit image

convert my-image.jpg -colorspace Gray -depth 2 my-image-gray.jpg 

Create sprite/pixel art

• Piskel
• Pixilart

Convert an image to a different resolution/pixel size

A few basic (but powerful) ImageMagick commands

convert image.jpg -resize 1024x768\! output_file.jpg

Anti-alias 修邊

• The prefix “anti-” in “antialiasing” means “against” or “opposite of”. So, “antialiasing” refers to the technique that is used to counter or prevent the effect of aliasing. Aliasing is a problem that causes different signals to become indistinguishable (or aliases of one another) when sampled. It often occurs in computer graphics when representing a high-resolution signal at a lower resolution. Anti-aliasing serves a simple purpose — fixing these jagged edges that show up in games and other computer graphics.
• What Is Anti-Aliasing, and How Does It Affect My Photos and Images?
• Anti-aliasing in R graphics under Windows (as per Mac)
• What is Anti-aliasing?
  • Methods of Anti-Aliasing (AA)
  • Types of Anti-Aliasing
  • Applications of Anti-Aliasing Techniques
• How to turn on anti-aliasing in games. What is anti-aliasing? MSAA, FXAA, TAA, and more explained

Upscayl: AI Image Upscaler

https://www.upscayl.org/ Upscayl helps you turn low resolution images into high resolution. Crisp and sharp! No internet required. 5+ Modes. Fully Customizable. Free and Open Source.

Convert an image file to a different format (eg icon)

• https://convertio.co/svg-png/
• Using the imagemagic program.

  convert winamp-ncrow.png -resize 32x32 winamp-ncrow.ico

• 4 Ways to Batch Convert Your PNG to JPG and Vice-Versa

Make an icon using GIMP

How to Make an Icon for Windows 10 or 11 Out of Any Image

Crop an image

• How to Crop an Image Into a Shape in Google Slides
• How to crop an image to a circle in R with {cropcircles}

Rotate an image

http://www.imagemagick.org/script/command-line-options.php#rotate

convert winamp-ncrow.png -rotate 45 winamp-ncrow2.png  # 45 degrees

One problem with this simple approach is the picture size (not image file) changed (become smaller) if the degree is not one of 90,180 or 270.

Create an animated gif file

Use the script here. See the last example on here. The rotation speed looks good too! Just change the source image file in the script.

#!/bin/sh
#
# Create a rotating figure using Distort SRT transformations
#
command='convert -delay 10 koala.gif -virtual-pixel white'

for i in `seq 5 5 360`; do
  command="$command \\( -clone 0 -distort SRT $i \\)"
done

command="$command -delete 0 -loop 0 animate_distort_rot.gif"

eval $command

chmod 644 animate_distort_rot.gif

Tool to convert a sequence of numbered PNG files to an animated GIF?. Convert command line option. The option '-loop 0' means repeats infinitely and '-delay 200' means 2 seconds delay between each frame.

convert -delay 200 -loop 0 file_1.png file_2.png file_3.png animated.gif

Combine/merge images

• Combine 3 images into one row

  convert image1.png image2.png image3.png +append output.png

• Combine 3 images into a 2x2 layout

  # Step 1
  convert image1.png image2.png +append row1.png
  convert image3.png null: +append row2.png
  
  # Step 2
  convert row1.png row2.png -append output.png

  The null: is used to create an empty space for the missing fourth image.

Creating a GIF from images/videos

The Best Ways to Make Your Own GIFs

Create a video from images

• ffmpeg

  # frame rate of 24 frames per second, using the libx264 (h264) codec
  ffmpeg -framerate 24 -pattern_type glob -i '*.jpg' -c:v libx264 output.mp4

• ImageMagick

  # The -delay option specifies the delay (50/100 = 0.5 seconds) between each frame, 
  # This means that the frame rate will be 1/0.5=2.
  # and -loop 0 makes the video loop indefinitely.
  # the default codec used for MP4 output is libx264
  convert -delay 50 -loop 0 *.jpg output.mp4

• av

  # frame rate of 2 frames per second, using the libx264 (h264) codec
  av -r 2 -i *.jpg -c:v libx264 output.mp4

• Mencoder

  # frame rate of 2 frames per second, using the MPEG-4 video codec (older than h264)
  mencoder "mf://*.jpg" -mf fps=2 -o output.mp4 -ovc lavc -lavcopts vcodec=mpeg4

Convert Video to GIF

The Best Ways to Convert Video to GIF

View images as Slideshow

• Image viewer
• I Turned a Raspberry Pi into a Private Slideshow Machine, Here's How

HDR/High Dynamic Range

How to Create Fake High Dynamic Range Photos in Photoshop

R packages

• imager: an R package for image processing, CRAN
• Color-Swapping Film Palettes in R with imager, ggplot2, and kmeans
• Creating typewriter-styled images in R

Annotate jpeg/png file

See graphics::rasterImage()

Edit gif file

gifsicle package

Background

Change white to transparent background

Set transparent background using ImageMagick and commandline prompt (it works)

convert test.png -transparent white transparent.png

Replace transparency in PNG images with white background

http://stackoverflow.com/questions/2322750/replace-transparency-in-png-images-with-white-background

convert image.png -background white -alpha remove white.png

Adobe lightroom

• How to Blur a Photo Background in Adobe Lightroom
• Best Free and Open Source Alternatives to Adobe Lightroom Classic

Online tools to remove background

• https://www.magiceraser.io/
• photoroom.com

Automatic background removal using R

Image segmentation in R: Automatic background removal like in a Zoom conference

Remove unwanted objects

• https://cleanupphotos.com/.
  • Download a video frame from YT. Open GIMP - New. Accept the default image size. Ctrl + v to paste the image from the clipboard. Choose "Image" -> "Crop to Content". Export to PNG.
  • I uploaded a png file. The saved file cannot be opened (Fatal error reading PNG image file: Not a PNG file). After I manually changed the extension to jpg and it works. The resolution of the saved image file is decreased however.
• Lama Cleaner - A free and open-source inpainting tool powered by SOTA AI model
• 切勿错过！终于在GitHub上找到10个超强悍的开源软件和免费项目！ | 零度解说. Lama Cleaner, Misskey, StockAI, NBlog, AutoCut, Pake, Fyrox, Tooll 3, SMSBoom, Flarum.

Remove GPS metadata from jpg files - exiftool

sudo apt-get install libimage-exiftool-perl
exiftool -gps:all= -xmp:geotag= image.jpg

The image file will be updated. To check the current metadata, use

exiftool image.jpg | grep GPS

Note that the above command only remove gps information. The other information like date/time of creation, camera model are not changed.

Exitftool can also be used to edit the metadata on PDF files.

exiftool -Title="This is the Title" -Author="Happy Man" -Subject="PDF Metadata" drawing.pdf

An R package exifr also available on CRAN.

Overlay the date and time onto an image

convert image.jpg -gravity SouthEast -pointsize 24 -fill orange \
        -annotate +10+10 "%[exif:DateTimeOriginal]" output.jpg

Note that if output.jpg is replaced with image.jpg, then image.jpg will be overwritten.

for img in *.jpg; do
  convert "$img" -gravity SouthEast -pointsize 24 -fill yellow -annotate +10+10 "%[exif:DateTimeOriginal]" "$img"
done

Inkscape

• https://inkscape.org/
• Using the Command Line

  inkscape --export-type=png --export-filename=output.png my_file.svg 
  inkscape --export-type=png --export-filename=- my_file.svg | convert - filename.jpg
  

Error: Failed to get connection

inkscape -C --export-type=png input.svg --export-filename=output.png
# OR
inkscape -C  input.svg --export-filename=output.png

I got an error when I tested on headless system https://bugs.launchpad.net/inkscape/+bug/1460797. Either command works, however, in a desktop system.

So inkscape in a headless system is not possible!

Edit Svg image

• Inkscape
• Inkscape from Fedora magazine
  • Getting started with Inkscape on Fedora
  • Inkscape: Adding some colour
  • Create a simple wallpaper with Fedora and Inkscape
• Logos By Nick (Youtube)

Stitch

MAKE MORE with Inkscape – Ink/Stitch

Animated gif

• How to generate a animated GIF or movie out of images on Linux (GIMP or PhotoFilmStrip)
• convert (.gif to .png) this image to get the original view? (ImageMagick)

Hue/saturation

• What is Color Saturation? (How to Understand and Use It). You can define saturation as the depth or intensity of color present in an image.
• How to Creatively Use Hue/Saturation Adjustments in Photoshop
• Color Saturation – The Ultimate Guide for Artists with examples.
• Understand The Basics Of Color Theory
• A Photographer’s Guide to Vibrance and Saturation (and their differences). Avoiding over-saturation, and Vibrance tool

Photoshop alternatives

• Photopea:
  • You can use the free version w/o creating an account.
  • Even the app is online but the processing takes place locally. Online Photoshop Alternatives: Which is Best?

What’s the Difference between Illustrator and Photoshop

What’s the Difference between Illustrator and Photoshop?

Adobe InDesign vs. Illustrator

Adobe InDesign vs. Illustrator: Which One Should You Use?

Display images in a terminal

• tiv/Terminal Image Viewer contains a mall C++ program. It works when I tested on a Ubuntu 22.04 box. I am using the commit version 7573de8 12/6/2023.

  git clone https://github.com/stefanhaustein/TerminalImageViewer.git
  
  g++ --version
  cd TerminalImageViewer/src
  make
  sudo make install
  
  tiv myimage.png

  

  File format is not rcognized. sudo apt install imagemagick solves the issue.

• Using FIM

Design

• How to Use Canva to Design Like a Professional
• Canva: The best 5 tips & tricks for beginners

Logos

The 4 Best Websites to Create a Logo for Your Business

Collage

• Easily Make Collages in Linux With PhotoCollage and Mountain Tapir Apps
• PhotoCollage

Recognize a doodling

• quickdraw.withgoogle.com
• scribblediffusion.com

OCR

• How To Convert Images To Text On The Linux Command Line With OCR
• Use gImageReader to Extract Text From Images and PDFs on Linux
• 6 Best Chinese OCR App to Recognize Chinese Characters (Online Incl.) Google Drive can do it too (not perfect from my testing).
• TextSnatcher - Amazoin, OPen Source, OCR for you Linux Desktop! , Github

iOS

How to Edit Photos on Your iPhone Using the Photos App: crop, change the aspect ratio of a photo, rotate a photo, make a mirror image of a photo, select frames from Live Photos, change a photo’s filter, Change the exposure, Adjust the brilliance, Adjust highlights, Adjust shadows, Create contrast, Brighten the photo, Enhance the colors (Adjust saturation, Adjust vibrancy)