Pixel-Based Graphics Editor

A desktop raster / pixel-art editor built in Java 17 (Swing) with a Kotlin layer engine. Full layer support, a rich drawing toolset with per-tool settings, command-pattern undo/redo, zoom-to-cursor navigation, and a native layered project format, all in one self-contained desktop app with light and dark FlatLaf themes.

Features

Layers (Kotlin engine)

• Add, delete, duplicate, merge down, reorder (buttons or drag-and-drop)
• Per-layer opacity and visibility, inline rename, right-click context menu
• Tools always draw on the active layer; structural operations are undoable
• Text lives on its own re-editable layer

Drawing tools, each with its own settings panel

• Brush: four styles (natural, spray, dotted, oil), continuous size up to 300 px, stroke opacity, and a live cursor size-ring. Strokes are composited once at the chosen opacity so overlapping segments don't darken at the joints
• Pencil: hard-edged, size up to 200 px, with opacity
• Eraser: erases to transparency, size up to 400 px
• Shape: rectangle, circle, line, triangle, pentagon, hexagon, with stroke width
• Text: any installed font, adjustable size and style
• Eyedropper with a loupe magnifier; flood fill

Colour

• Photoshop-style HSV picker (saturation/value square + hue bar) docked in the UI
• Current swatch, recent colours, and a full system chooser for custom colours

Selection (Kotlin)

• Marquee select, move, copy/cut/paste/delete, select-all, recolour region

Transform

• Rotate / flip the whole document (every layer together, adopting swapped dimensions on quarter-turns) or just the current selection

Navigation

• Mouse-wheel and Ctrl+wheel zoom-to-cursor; spacebar-drag or middle-drag panning
• Status bar with live zoom %, Fit, and 100% buttons

Files

• Native .pxe project format: a ZIP of one PNG per layer plus a manifest, round-tripping the full layer stack (order, names, opacity, visibility)
• Import PNG/JPEG/BMP; export flattened PNG/JPEG/BMP
• Custom canvas sizes with presets, autosave, safe-exit prompt

Workspace

• Light and dark themes (FlatLaf), toggled from the Home menu and remembered
• Resizable, persisted panel layout with Reset Layout; in-app help for every tool

Built with

Java 17, Kotlin, Swing, FlatLaf, Gradle. The layer engine, selection tool, and safe-exit flow are Kotlin; the UI, tools, and command system are Java. The two interoperate directly in one Gradle build.

Getting started

Install: grab the Windows installer from the Releases page. No JDK needed, the runtime is bundled.

Build from source: requires JDK 17.

./gradlew run     # build and launch
./gradlew test    # run the headless unit tests

On Windows, use gradlew.bat in place of ./gradlew. The in-app help (Ctrl+H) documents every tool. User settings (panel layout, first-run flags) are stored in ~/.pixeleditor.

Packaging

./gradlew jpackage    # native installer in build/dist

Uses the JDK's jpackage; on Windows the .msi type requires the WiX Toolset 3.x. Change --type to app-image in build.gradle for a plain runnable folder with no extra tooling.

Keyboard shortcuts

Action	Shortcut
Brush / Pencil / Eraser / Eyedropper	B / P / E / I
Shape / Select / Zoom / Text	S / C / Z / T
Select all / Deselect	Ctrl+A / Esc
Undo / Redo	Ctrl+Z / Ctrl+Y
Save / Save As	Ctrl+S / Ctrl+Shift+S
New / Open	Ctrl+N / Ctrl+O
Help / Exit	Ctrl+H / Ctrl+Q

Architecture notes

• Layer stack: CanvasPanel owns a LayerStack (Kotlin); the active layer is the drawing surface, so every tool and command operates on it unchanged. Rendering composites visible layers bottom-to-top over a checkerboard.
• Undo/redo: command pattern (commands/), covering pixel edits and structural layer operations (delete, duplicate, merge, resize, rotate).
• Coordinates: one source of truth (screenToImage / imageToScreen) folds zoom, pan, and centering, shared by the renderer and all tools.
• Tests: a headless JUnit 5 suite covers the layer engine (stack operations, compositing, resize) without needing a display.

What I'd do next

• Extend test coverage to the undo/redo command classes and the .pxe round-trip (needs the file dialogs factored out of Project)
• An application icon for the packaged build
• Per-layer blend modes (multiply, screen, overlay)
• Selection transforms beyond rotate (free scale, skew)

Licence

MIT, see LICENSE.