GIMP – GNU Image Manipulation Program

Introduction to GIMP

GIMP (GNU Image Manipulation Program) is a free, open-source raster graphics editor used for image manipulation, photo retouching, image composition, and image authoring. First released in 1996, GIMP has evolved into a powerful alternative to commercial image editors like Adobe Photoshop, offering an extensive set of tools for professional-quality image editing without the subscription costs associated with proprietary software.

GIMP is developed by a global community of volunteers and is released under the GNU General Public License, ensuring it remains free and open-source. The software supports numerous file formats, offers sophisticated tools for photo manipulation, and provides a customizable interface that can be adapted to individual workflows. With its plugin architecture and scripting capabilities, GIMP can be extended to meet virtually any image editing need.

Key Features and Capabilities

GIMP provides a comprehensive suite of image editing tools that rival commercial alternatives. Core features include layers with blend modes, channels, masks, paths, and comprehensive selection tools. The software supports full alpha channel management, allowing for sophisticated compositing and transparency effects. Advanced color management with ICC color profile support ensures accurate color reproduction for professional workflows.

The software excels in photo retouching with tools like the healing brush, clone tool, and perspective correction. GIMP supports high-bit-depth images (16-bit and 32-bit per channel), non-destructive editing through adjustment layers, and raw image processing through integration with external tools like darktable and RawTherapee. Its extensive filter collection and plugin ecosystem provide endless possibilities for creative effects and automation.

Installation on Linux

GIMP is available in virtually all Linux distribution repositories and through universal package formats.

Installing on Ubuntu/Debian

# Install GIMP from official repositories
sudo apt update
sudo apt install gimp

# Install additional plugins and brushes
sudo apt install gimp-plugin-registry gimp-data-extras

# Install GIMP Help documentation
sudo apt install gimp-help-en

# Launch GIMP
gimp

Installing via Flatpak (Recommended for Latest Version)

# Add Flathub repository
flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

# Install GIMP
flatpak install flathub org.gimp.GIMP

# Run GIMP
flatpak run org.gimp.GIMP

# Update GIMP
flatpak update org.gimp.GIMP

Installing via Snap

# Install GIMP via Snap
sudo snap install gimp

# Launch GIMP
gimp

Installing on Fedora

# Install GIMP
sudo dnf install gimp

# Install additional plugins
sudo dnf install gimp-resynthesizer gimp-separate+ gimp-lqr-plugin

# Install GIMP Help
sudo dnf install gimp-help

Installing on Arch Linux

# Install from official repositories
sudo pacman -S gimp

# Install optional dependencies
sudo pacman -S gimp-help-en gutenprint

# Install plugins from AUR
yay -S gimp-plugin-gmic gimp-plugin-resynthesizer

Installing on openSUSE

# Install GIMP
sudo zypper install gimp

# Install additional plugins
sudo zypper install gimp-plugins-python gimp-plugin-lqr

Compiling from Source

# Install build dependencies (Ubuntu)
sudo apt install build-essential meson ninja-build \
    libbabl-dev libgegl-dev libglib2.0-dev \
    libgtk-3-dev libpango1.0-dev libcairo2-dev \
    python3-dev intltool

# Clone repository
git clone https://gitlab.gnome.org/GNOME/gimp.git
cd gimp

# Build with Meson
meson setup _build --prefix=/usr/local
ninja -C _build
sudo ninja -C _build install

Installation on Windows

GIMP for Windows is available through multiple installation methods.

Installing via Direct Download

# Download from gimp.org
# Run the installer gimp-x.x.x-setup.exe
# Choose installation options:
#   - Full installation (recommended)
#   - Customization available for file associations
# Complete installation wizard

Installing via Winget

# Install using Windows Package Manager
winget install GIMP.GIMP

# Upgrade GIMP
winget upgrade GIMP.GIMP

Installing via Chocolatey

# Install using Chocolatey
choco install gimp

# Upgrade GIMP
choco upgrade gimp

Portable Installation

# Download GIMP Portable from PortableApps.com
# Extract to USB drive or desired location
# Run GIMPPortable.exe
# Settings stored in portable directory

Installation on macOS

GIMP is available for macOS through Homebrew or direct download.

Installing via Homebrew

# Install GIMP
brew install --cask gimp

# Launch GIMP
open -a GIMP

Installing via Direct Download

# Download DMG from gimp.org
# Choose version for your architecture:
#   - Apple Silicon (ARM64)
#   - Intel (x86_64)
# Open DMG and drag GIMP to Applications
# Launch from Applications or Spotlight

Interface Overview

Understanding GIMP’s interface is essential for efficient workflow.

Single-Window Mode

# Enable single-window mode (recommended):
Windows > Single-Window Mode

# Default panels:
# Left: Toolbox with tool options
# Center: Canvas with tabs for multiple images
# Right: Layers, Channels, Paths, Undo History

Customizing the Interface

# Dockable Dialogs:
Windows > Dockable Dialogs > [Select dialog]

# Available dialogs:
# - Layers
# - Channels
# - Paths
# - Colors
# - Brushes
# - Patterns
# - Gradients
# - Fonts
# - Tool Options
# - Histogram
# - Navigation

# Save workspace:
Windows > Save Window Layout

Essential Tools and Operations

GIMP provides comprehensive tools for image manipulation.

Selection Tools

# Rectangle Select (R)
# Select rectangular regions
# Hold Shift for square selection
# Hold Ctrl to select from center

# Ellipse Select (E)
# Select elliptical/circular regions
# Hold Shift for circle

# Free Select/Lasso (F)
# Freehand selection by drawing

# Fuzzy Select/Magic Wand (U)
# Select by color similarity
# Adjust Threshold for sensitivity

# Select by Color (Shift+O)
# Select all pixels of similar color

# Scissors Select (I)
# Intelligent edge-following selection

# Foreground Select
# Extract foreground objects interactively

Transform Tools

# Move (M)
# Move layers, selections, or paths

# Align
# Align and distribute layers

# Crop (Shift+C)
# Crop image to selection

# Rotate (Shift+R)
# Rotate layer or selection

# Scale (Shift+S)
# Resize layer or selection

# Shear (Shift+H)
# Shear transformation

# Perspective (Shift+P)
# Perspective transformation

# Flip (Shift+F)
# Flip horizontally or vertically

# Cage Transform (Shift+G)
# Deform using control points

# Warp Transform (W)
# Interactive warping

Paint Tools

# Paintbrush (P)
# Paint with brush dynamics

# Pencil (N)
# Hard-edged painting

# Airbrush (A)
# Soft spray painting

# Ink
# Calligraphy-style painting

# Clone (C)
# Clone from source area

# Healing (H)
# Heal imperfections

# Perspective Clone
# Clone with perspective correction

# Blur/Sharpen
# Local blur or sharpening

# Smudge (S)
# Smudge pixels

# Dodge/Burn (Shift+D)
# Lighten or darken areas

Color Tools

# Color Picker (O)
# Sample colors from image

# Bucket Fill (Shift+B)
# Fill with color or pattern

# Gradient (G)
# Create gradient fills

# Color Balance (Colors > Color Balance)
# Adjust color balance

# Curves (Colors > Curves)
# Precise tonal adjustments

# Levels (Colors > Levels)
# Adjust input/output levels

# Hue-Saturation (Colors > Hue-Saturation)
# Adjust hue, saturation, lightness

Keyboard Shortcuts

Master these shortcuts for efficient workflow.

File Operations

Ctrl+N              New image
Ctrl+O              Open image
Ctrl+Alt+O          Open as layers
Ctrl+S              Save (XCF format)
Ctrl+Shift+S        Save As
Ctrl+Shift+E        Export As
Ctrl+E              Export (overwrite)
Ctrl+W              Close image
Ctrl+Q              Quit GIMP

Edit Operations

Ctrl+Z              Undo
Ctrl+Y              Redo
Ctrl+X              Cut
Ctrl+C              Copy
Ctrl+V              Paste
Ctrl+Shift+V        Paste as new image
Delete              Clear selection
Ctrl+A              Select all
Ctrl+Shift+A        Select none
Ctrl+I              Invert selection

View Controls

+/=                 Zoom in
-                   Zoom out
1                   Zoom to 100%
Shift+Ctrl+E        Fit image in window
Shift+Ctrl+J        Fit selection in window
Space               Pan (hold and drag)
Tab                 Toggle tool options
Shift+Ctrl+T        Toggle toolbox
Shift+Ctrl+L        Toggle layers dialog

Layer Operations

Ctrl+Shift+N        New layer
Ctrl+Shift+D        Duplicate layer
Ctrl+M              Merge down
Ctrl+Shift+M        Flatten image
Page Up             Select layer above
Page Down           Select layer below
Home                Select top layer
End                 Select bottom layer

Tool Shortcuts

R                   Rectangle select
E                   Ellipse select
F                   Free select
U                   Fuzzy select
P                   Paintbrush
N                   Pencil
C                   Clone
H                   Heal
M                   Move
Shift+S             Scale
Shift+R             Rotate
G                   Gradient
Shift+B             Bucket fill
T                   Text
Z                   Zoom
X                   Swap foreground/background
D                   Default colors (black/white)

Working with Layers

Layers are fundamental to non-destructive editing in GIMP.

Layer Operations

# Create new layer:
Layer > New Layer
# Or Ctrl+Shift+N

# Layer options:
Name: Layer name
Width/Height: Dimensions
Fill with: Transparency/White/Black/Foreground/Background

# Duplicate layer:
Layer > Duplicate Layer
# Or Ctrl+Shift+D

# Merge layers:
Layer > Merge Down (Ctrl+M)
Layer > Flatten Image (Ctrl+Shift+M)
Image > Merge Visible Layers

Layer Blend Modes

# Common blend modes:
Normal          - Standard blending
Multiply        - Darkens image
Screen          - Lightens image
Overlay         - Increases contrast
Soft Light      - Subtle contrast
Hard Light      - Strong contrast
Difference      - Inverts based on brightness
Addition        - Adds pixel values
Subtract        - Subtracts pixel values
Darken Only     - Shows darker pixels
Lighten Only    - Shows lighter pixels
Color           - Applies hue and saturation
Luminosity      - Applies brightness only

Layer Masks

# Add layer mask:
Layer > Mask > Add Layer Mask

# Mask options:
White (full opacity)    - Layer fully visible
Black (full transparency) - Layer fully hidden
Layer's alpha channel   - Based on existing transparency
Selection              - Based on current selection
Grayscale copy         - Based on image luminosity

# Edit mask:
# Click mask thumbnail to edit
# White reveals, black conceals
# Use gradients for smooth transitions

# Apply/Remove mask:
Layer > Mask > Apply Layer Mask
Layer > Mask > Delete Layer Mask

Photo Editing Techniques

Common photo editing workflows in GIMP.

Basic Photo Corrections

# Auto-enhance:
Colors > Auto > Normalize
Colors > Auto > White Balance
Colors > Auto > Stretch Contrast

# Levels adjustment:
Colors > Levels
# Adjust Input Levels sliders
# Move black point right to deepen shadows
# Move white point left to brighten highlights

# Curves adjustment:
Colors > Curves
# S-curve for contrast
# Pull up curve to brighten
# Pull down to darken

Removing Blemishes

# Healing Tool (H):
1. Set brush size slightly larger than blemish
2. Ctrl+Click to set source (clean skin area)
3. Click on blemish to heal

# Clone Tool (C):
1. Set brush and opacity
2. Ctrl+Click to set clone source
3. Paint over area to replace

# Spot Healing (via Resynthesizer):
1. Select blemish with any selection tool
2. Filters > Enhance > Heal Selection
3. Adjust settings and apply

Background Removal

# Method 1: Fuzzy Select
1. Use Fuzzy Select (U) on background
2. Adjust Threshold for better selection
3. Select > Grow (2-3 pixels)
4. Delete or cut selection

# Method 2: Foreground Select
1. Select Foreground Select tool
2. Draw rough outline around subject
3. Paint over foreground (blue)
4. Press Enter to create selection
5. Invert and delete background

# Method 3: Paths
1. Use Paths tool (B)
2. Trace subject outline
3. Selection from Path
4. Invert and delete

# Add alpha channel first:
Layer > Transparency > Add Alpha Channel

Text and Typography

GIMP provides comprehensive text editing capabilities.

Creating Text

# Text Tool (T):
1. Select Text tool
2. Click on canvas
3. Type text in editor

# Text options:
Font: Select typeface
Size: Font size
Color: Text color
Justify: Left/Center/Right/Fill
Line spacing: Adjust line height
Letter spacing: Adjust kerning

# Convert to path:
Layer > Text to Path
# Allows vector editing of text shape

# Convert to selection:
Layer > Text to Selection

Text Effects

# Drop Shadow:
Filters > Light and Shadow > Drop Shadow
# Adjust X/Y offset, blur radius, color

# Outline Text:
1. Layer > Text to Selection
2. Select > Grow (2-5 pixels)
3. New layer below text
4. Fill selection with outline color

# Gradient Text:
1. Layer > Text to Selection
2. Fill with gradient

# 3D Text:
Filters > Alpha to Logo > [Choose effect]

Filters and Effects

GIMP includes extensive built-in filters and supports external plugins.

Blur Filters

# Gaussian Blur:
Filters > Blur > Gaussian Blur
# Adjust horizontal/vertical radius

# Motion Blur:
Filters > Blur > Motion Blur
# Type: Linear/Radial/Zoom
# Adjust angle and length

# Lens Blur:
Filters > Blur > Lens Blur
# Simulates depth-of-field effect

Distort Filters

# Liquify (IWarp):
Filters > Distorts > IWarp
# Interactive warping

# Spherize:
Filters > Distorts > Spherize
# Wrap image around sphere

# Waves:
Filters > Distorts > Waves
# Create wave distortion

Enhance Filters

# Sharpen (Unsharp Mask):
Filters > Enhance > Sharpen (Unsharp Mask)
# Amount: 50-150%
# Radius: 0.5-2 pixels
# Threshold: 0-10 levels

# Noise Reduction:
Filters > Enhance > Noise Reduction

# Red Eye Removal:
Filters > Enhance > Red Eye Removal

Batch Processing with GIMP

Automate repetitive tasks with scripts and batch processing.

Script-Fu Console

# Access Script-Fu console:
Filters > Script-Fu > Console

# Basic Script-Fu commands:
; List all functions
(gimp-procedural-db-dump "/tmp/gimp-functions.txt")

; Get image dimensions
(gimp-image-width image)
(gimp-image-height image)

; Create new image
(gimp-image-new 1920 1080 RGB)

; Get current image and drawable
(car (gimp-image-list))
(car (gimp-image-get-active-layer image))

Python-Fu Scripts

# Python-Fu batch resize script
# Save as batch_resize.py in GIMP plugins folder

#!/usr/bin/env python
from gimpfu import *
import os

def batch_resize(input_dir, output_dir, new_width):
    for filename in os.listdir(input_dir):
        if filename.lower().endswith(('.png', '.jpg', '.jpeg')):
            filepath = os.path.join(input_dir, filename)
            image = pdb.gimp_file_load(filepath, filename)
            
            # Calculate new height maintaining aspect ratio
            ratio = float(new_width) / image.width
            new_height = int(image.height * ratio)
            
            # Scale image
            pdb.gimp_image_scale(image, new_width, new_height)
            
            # Export
            drawable = pdb.gimp_image_get_active_layer(image)
            output_path = os.path.join(output_dir, filename)
            pdb.file_png_save(image, drawable, output_path, filename,
                            0, 9, 0, 0, 0, 0, 0)
            
            pdb.gimp_image_delete(image)

register(
    "batch_resize",
    "Batch resize images",
    "Resize all images in a directory",
    "Author", "Author", "2024",
    "/Filters/Batch/Resize...",
    "",
    [
        (PF_DIRNAME, "input_dir", "Input Directory", ""),
        (PF_DIRNAME, "output_dir", "Output Directory", ""),
        (PF_INT, "new_width", "New Width", 1920),
    ],
    [],
    batch_resize
)

main()

Command-Line Batch Processing

# Batch convert using GIMP from command line
# Linux/macOS:
for file in *.png; do
    gimp -i -b "(let* ((image (car (gimp-file-load RUN-NONINTERACTIVE \"$file\" \"$file\"))) (drawable (car (gimp-image-get-active-layer image)))) (file-jpeg-save RUN-NONINTERACTIVE image drawable \"${file%.png}.jpg\" \"${file%.png}.jpg\" 0.9 0 0 0 \"\" 0 0 0 0) (gimp-image-delete image))" -b "(gimp-quit 0)"
done

# Simpler with gimp-console (if available):
gimp-console -i -b '(batch-process "/input/*.png" "/output/" jpeg)' -b '(gimp-quit 0)'

Plugins and Extensions

Extend GIMP’s capabilities with plugins.

Popular Plugins

# G'MIC (GREYC's Magic for Image Computing)
# Hundreds of filters and effects
# Install: flatpak install flathub org.gimp.GIMP.Plugin.GMic

# Resynthesizer
# Content-aware fill and texture synthesis
# Ubuntu: sudo apt install gimp-plugin-registry

# BIMP (Batch Image Manipulation Plugin)
# GUI for batch processing

# Separate+
# CMYK color separation for print

Plugin Installation Locations

# Linux:
~/.config/GIMP/2.10/plug-ins/
~/.config/GIMP/2.10/scripts/

# Windows:
%APPDATA%\GIMP\2.10\plug-ins\
%APPDATA%\GIMP\2.10\scripts\

# macOS:
~/Library/Application Support/GIMP/2.10/plug-ins/
~/Library/Application Support/GIMP/2.10/scripts/

# Make plugins executable (Linux/macOS):
chmod +x ~/.config/GIMP/2.10/plug-ins/plugin-name.py

Color Management

Configure GIMP for accurate color reproduction.

Color Management Settings

# Edit > Preferences > Color Management

# Mode of operation:
Color managed display

# RGB Profile:
sRGB (default) or Adobe RGB

# CMYK Profile:
Select appropriate print profile

# Monitor Profile:
Use system-installed profile

# Rendering Intent:
Perceptual (photos)
Relative Colorimetric (graphics)

Working with Profiles

# Assign profile:
Image > Color Management > Assign Color Profile

# Convert to profile:
Image > Color Management > Convert to Color Profile

# Soft proofing:
View > Color Management > Soft-proof

Troubleshooting

Solutions for common GIMP issues.

Performance Issues

# Increase memory allocation:
Edit > Preferences > System Resources
Tile Cache Size: 4096 MB (adjust based on RAM)
Maximum New Image Size: Increase for large files

# Reduce undo levels:
Edit > Preferences > Environment
Minimal number of undo levels: 15
Maximum undo memory: 256 MB

Reset GIMP Settings

# Backup and reset (Linux):
mv ~/.config/GIMP/2.10 ~/.config/GIMP/2.10.backup
gimp  # Creates fresh configuration

# Windows:
Rename %APPDATA%\GIMP\2.10 to 2.10.backup

# macOS:
mv ~/Library/Application\ Support/GIMP/2.10 ~/Library/Application\ Support/GIMP/2.10.backup

Conclusion

GIMP stands as a testament to the power of open-source software development, providing professional-grade image editing capabilities entirely free of charge. While it may have a steeper learning curve than some commercial alternatives, the investment in learning GIMP pays dividends in the form of a powerful, flexible tool that can handle virtually any image editing task. With its active development community, extensive plugin ecosystem, and comprehensive feature set, GIMP continues to be an essential tool for photographers, designers, and digital artists who value both capability and freedom.