Graphics software: Gimp, Inkscape, ImageMagick, Blender, ShareX.

• Image Viewers: IrfanView, HoneyView, and FastStone.
• Gimp is a free, open source, and extremely powerful image editing program that offers the kind of functionality usually associated with top end, expensive software developed for professionals like Adobe Photoshop.

GIMP is expandable and extendible. You can install new brushes (Techzillo, Noupe), patterns, gradients, plug-ins, and scripts. How to install them? Find the appropriate folder (Edit, Preferences, Folders) and drop them there. G’MIC is a full-featured open-source framework for digital image processing. G’MIC-Qt is a plug-in to bring G’MIC capabilities to GIMP and other image editing programs. Once that you have installed it, you will have it accessible in Filters, G’MIC-Qt…

Some tips. Round corners of an image: Filters, Decor, Rounded Corners. Scaling/resizing photos: Go to the menu Image and choose Scale Image (Interpolation: NoHalo and LoHalo reduce the blur in the resampled images). Sharpen an image: Filters, Enhance, Sharpen (Unsharp Mask). Blur an image: Filters, Blur, Gaussian Blur… Adjust brightness: Colours, Brightness-Contrast… or Colours, Curves. Create a shadow effect: A. Write your text on the canvas by selecting Tool, and then Text, by clicking the tool icon A or by using the T keyboard shortcut. B. Filters, Light and Shadows, Drop Shadow.

Create a text outline: A. Write your text. Then, right-click on the text and select Path from Text. B. Create a new layer (Layer, New Layer. Fill with: Transparency). C. Select, From Path, and then go to the menu Select again, and choose Grow (4-5 pixels). D. Select the bucket tool (Tools, Paint Tools, Bucket Fill or the shorcut Shift+B) and fill the selected area. E. De-select with Select, None. F. Move the layer with the outline down.

• Inkscape is a professional vector graphics editor for Windows, macOS, and Linux. It’s free and open source. It’s similar to Adobe Illustrator.

• Others: Pinta “is a free, open source program for drawing and image editing. Its goal is to provide users with a simple yet powerful way to draw and manipulate images on Linux, Mac, and Windows.” Krita is a professional free and open source painting program. MyPaint “is a a nimble, distraction-free, and easy tool for digital painters. It lets you focus on the art instead of the program. You work on your canvas with the minimum distractions, bringing up the interface only when you need it.”

• Free Screenshots Apps: Greenshot “is a light-weight screenshot software tool for Windows.”

  

  ShareX is a free, open source advanced screenshot capture, screen capture, file sharing, and productivity application.

• Blender “is a free and open source 3D animation suite. It supports the entirety of the 3D pipeline —modeling, rigging, animation, simulation, rendering, compositing and motion tracking, even video editing and game creation.”

• 3D modeling software and character design (free alternatives to Poser, Character Creator 3, iClone): Mixamo “allows you to create, rig and animate unique characters for your projects.” MakeHuman is a free and open source 3D character creator. VRoid Studio is a free 3d anime characters creation tool. Unreal Engine is an open and advanced real-time 3D creation platform for photoreal visuals and immersive experiences.

Command-line Tools

• ImageMagick is a free and open-source cross-platform software suite for displaying, creating, converting, modifying, and editing raster images. It is designed for batch processing of images. Let’s see some examples.

1. Display a single file/all the files in a directory: display myImage.jpg / display *.png.

2. Flip image in the vertical/horizontal direction: display -flip myImage.jpg / display -flop myImage.jpg.

3. Convert [a single file/all the files in a directory] between image formats: convert bridge.jpg -monochrome bridgeMonochrome.jpg (it transforms bridge.jpg to black and white) / convert *.jpg *.png.

   convert’s syntax format is as follows: convert inputFileName [options] outputFileName

4. Improve brightness/contrast of the image: convert -brightness-contrast 20x8 myImage.jpg output.jpg

5. Resize an image: convert -resize 800x600 myImage.jpg output.jpg, convert -resize “50%” myImage.jpg Backup/resizeMyImage.jpg (resize an image by percentage and save it on another folder).

6. Blur images: convert -blur 2x3 myImage.jpg output.jpg

7. Add text: convert -font Helvetica -fill white -gravity SouthEast -annotate +0+10 ‘The bridge’ bridge.jpg output.jpg (gravity SouthEast moves the text to the bottom right of the image, font renders text with a particular font, fill defines the color).

8. Swirl images pixels about the center: convert -swirl 180 myImage.jpg output.jpg

9. We can use scripts for batch-processing of the images.

        for j in *.jpg
        do 
             convert -monochrome "$j" altered_"$j"
        done

• Image Viewer: sudo apt install sxiv. To see an image, just type in the terminal: sxiv bangkok.jpg. If you want to display all images in a directory, the command is as follows: sxiv ./misImagenes/*. Right click with the mouse and you will be able to see all the pictures in “thumbnail mode”.
• Taking screenshot in GNU/Linux using command line tools. ImageMagick: import -window root myScreenshot.png (it takes a screenshot of the entire screen), import myScreenshot.png (it takes a screenshot of an specific area).

Deepin Scrot is GNU/Linux Deepin’s screenshot program: scrot myScreenshot.png (it takes a screenshot of the entire screen), scrot -s myScreenshot.png (it takes a screenshot of an specific area).