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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.