gimp

GIMP is a feature-rich image editor with over two decades of active development. It covers professional image editing needs including photo retouching, image composition, and graphic design workflows.

• Layer, channel, and path editing comparable to Photoshop's non-destructive workflow
• Advanced color management with ICC profile support for print-ready output
• Hundreds of built-in filters and effects including blur, sharpen, distort, and noise reduction
• Script-Fu and Python-Fu scripting for batch processing and custom filter creation
• Extensible plugin ecosystem maintained by an active community
• Broad file format support including PSD, TIFF, PNG, JPEG, and WebP

Built in C on the GTK toolkit, GIMP runs on Windows, macOS, and Linux. Completely free with no restrictions on commercial use, it maintains a strong user base in Japan with full Japanese UI support.