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…
Open a new file: File, Open… Save your work: File, Save. XCF is the native file format for GIMP. It saves all the information about an image (layers, transparency settings, paths, etc.) Save Images as PNGs: File, Export As (or use the Shift, Ctrl, + E shortcut), select the File Type to convert the image into your desired format, choose PNG Image, and then smash the Export button.
Add coffee stains to your image: Filters, Decor, Coffee Stain… Age a photo/Make it look vintage: Filters, Decor, Old Photo… Rounded corners in GIMP: Filters, Decor, Rounded Corners. Alvin Alexander has a gallery of 130+ Gimp filters/effects.
If you want to make a fancy border around an image: 1. Increase your image canvas size: Image, Canvas Size, and smash the Center button (it allows you to center the image on the canvas). 2. Create a path around the image: Click the layer, then Alpha to Selection (it selects everything in the current layer that is not transparent), Select To Path (it convert the previous selection to a path), and Select, None. 3. Draw the border using the previous path: Edit, Stroke Path, select Stroke with a paint tool, e.g., Sparks.
Sharpen an image: Filters, Enhance, Sharpen (Unsharp Mask).
You can also (1) remove noise from the image (Filter, Enhance, Noise Reduction, and rename this layer as “Noise Reduction”). Then, duplicate this layer two times (Layer, Duplicate Layer or Shift+Ctrl+D). (2) Use High Pass in the first duplicated layer (Filters, Enhance, High Pass), rename this new layer as “HighPass”, change its blender mode from Normal to Vivid Light. Finally, (3) you could apply the Sharpen filter to the last duplicated layer (Filter, Enhance, Sharpen (Unsharp Mask)) and rename the layer as “Unsharp Mask”.
Scaling/resizing photos: Go to the menu Image and choose Scale Image
Blur an image: Filters, Blur, Gaussian Blur…
Adjust brightness/contrast: Colours, Brightness-Contrast… or Colours, Curves. An “S” curve is a quick way to boost your picture’s contrast, it is used to darken your shadows and brighten your highlights.
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. Then, apply the Drop Shadow filter: 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 (it creates a path from the text). B. Create a new layer (Layer, New Layer. Fill with: Transparency). C. Select, From Path (it creates a selection from the active path), and then go to the menu Select again, and choose Grow (4-5 pixels, it increases the selected area). D. Select the bucket tool (Tools, Paint Tools, Bucket Fill or use the shortcut Shift+B) and fill the selected area with black. E. De-select with Select, None. F. Move the layer with the outline down.
Create a gradient stroke: A. Write your text. B. Right-click on the text layer and choose Alpha to Selection (it selects our text). C. Grow/Increase your selection: Select, Grow (4px, it increases the selected area). D. Grab the Gradient tool to make a smooth transition between multiple colors, e.g., Full saturation spectrum CW. E. Deselect: Select, None.
Create a long shadow. After writing your text, select Filters, Light and Shadow, Long Shadow.
Personalize Gimp. Edit, Preferences, Interface, Theme (e.g., Light), Icon Theme (e.g., Color), Toolbox (e.g. uncheck Use Tool groups because we don’t want Gimp to group some tools), etc. Besides, you can reassign some keys: Edit, Keyboard Shortcuts.
Cartoonify your pictures or photos: Filters, Artistic, Cartoon. Another option is Filters, G’MIC-Qt…, Artistic, Cartoon. Of course, you need to have previously installed G’MIC.
Highlighting an image or text. A. Use the Rectangle Select Tool to select the area you want to highlight. B. Create a new transparent layer by selecting Transparency in the Layer Fill Type. C. Click on Foreground color, select a yellow color, click and drag it onto your selected area. D. Finally, select Multiply from the Mode dropdown menu in the Layers pane to change the blending mode.
Create a cool text effect. We are going to use three layers. The bottom one has a black background (Bucket Fill), the middle layer has the text itself (use the Text and Alignment tools to create the text and align it in your canvas), and the top one has been created with Layers, New From Visible (it creates a new layer filled with the image as it currently appears, it is labeled as “Visible”).
Then, we apply a blur filter on this layer: Filters, Blur, Gaussian Blur. Next, we create a new layer (“MyPlasma”), add some Plasma noise to this layer (Filters, Render, Noise, Plasma…), and apply a bump map filter (Filters, Map, Bump Map…). Click on Aux Input button and select the Visible layer.
Finally, we add a mask to the layer (Layer, Mask, Add Layer Mask…), copy the visible layer (Ctrl+C), select MyPlasma’s mask and paste the visible layer (Ctrl+V).