A simple, stand-alone mask painting tool for making clean RGB/CMY region masks (for SDXL / ComfyUI regional prompting, etc.). Load an image, paint directly on top of it, then export a pure-color mask PNG.

Core tools

• Brush: Paints with a configurable brush size. Supports Square or Circle brush shapes.

• Line: Click once to set a start point, release to place the end point and draw a straight line using the current brush size/shape (for nice straight borders).

• Polygon: Click to drop points, then close the shape to fill it.

  • Close by clicking near the first point (it highlights) or double-click to close.

  • In polygon mode, right-click removes the last point (useful for fixing a misclick).

• Fill: Flood-fills a contiguous area of the current mask layer based on the region’s existing mask color (designed to work with the tool’s pure RGB/CMY colors).

• Erase: Removes mask paint (transparent). When Erase is selected, color buttons are disabled because erase doesn’t use color.

Colors (pure mask output)

You can paint with 6 pure channels:

• RGB: Red, Green, Blue

• CMY: Cyan, Magenta, Yellow
  Export normalization ensures the saved mask is strictly pure channel colors (plus black background), even if your strokes had edge/preview artifacts.

UI + workflow features

• Load Image: Imports your guide image and enables the masking UI.

• Opacity slider: Controls how strong the mask overlay preview appears on top of the guide image (view-only; export stays pure).

• Brush size slider + numeric input (px): Fast adjustment with an exact value box.

• Undo / Redo: Buttons plus shortcuts (Ctrl+Z, Ctrl+Y / Ctrl+Shift+Z), with a history stack.

• Clear: Wipes the current mask layer.

• Export Mask: Saves a PNG named <original_filename>_mask.png, with black background and normalized pure RGB/CMY paint.

• Pan & Zoom: Right-click drag to pan, mouse wheel to zoom toward cursor for precise edits on large images.