Pixel-by-Pixel

Pixel-by-pixel tools paint the label directly onto the image, pixel by pixel, on the overlay of the active label. The Pixel-by-pixel section of the labeling bar provides three tools, each with its own settings dialog (the gear button next to the tool).

Tool	Shortcut	Description
Contour Filling	`F`	Detect the contours in the image and fill an enclosed area in a single click.
Paintbrush	`B`	Paint the label freehand with a brush of a chosen shape and size.
Magic Pen	`M`	Fill a region by selecting pixels of a similar color to the one clicked.

Contour Filling

When activated, Contour Filling analyzes the image to detect its contours (edge detection). The detected contours are previewed on top of the image, and an Apply / Cancel bar appears. Click inside an enclosed area to fill it with the active label’s color, then apply.

Settings:

Parameter	Range	Description
Tolerance	`1` – `20`	Controls how sensitive the contour detection is. A low level (e.g. 1) detects only strong, clean, well-defined edges (ultra precise). A high level (e.g. 20) captures faint and fragmented edges (maximum tolerance), at the cost of more noise. Each level shows a short description (e.g. Level 10 – Adaptive: Balances faint edge capture with minimal noise).

Paintbrush

The Paintbrush paints the active label freehand: hold the mouse button and drag over the image to color pixels with the label’s color.

Settings:

Parameter	Range / Options	Description
Brush Type	circle, square, diamond, star, triangle, cross, x, hexagon, spray, soft	The shape of the brush used to paint.
Brush Size	`1` – image size (pixels)	The size of the brush in pixels. The maximum is bounded by the dimensions of the current image.

Tip: If you draw a closed shape with the Paintbrush, you can fill it directly.

Magic Pen

The Magic Pen fills a region by comparing pixel colors: click on a pixel, and all neighboring (or all) pixels whose color is close enough to it are colored with the active label.

Settings:

Parameter	Range / Options	Description
Tolerance	`0` – `100` (%)	How similar a pixel’s color must be to the clicked color to be included. A higher tolerance includes a wider range of colors.
Max Pixels	`5000` – `500000`	The maximum number of pixels the fill can color, to keep the operation bounded.
Method	RGB, HSV	The color space used to compare colors. RGB compares raw color channels; HSV compares hue/saturation/value.
Logic	Pen logic, All color logic	Pen logic grows the selection from the clicked point, keeping only the connected region. All color logic selects every pixel of a similar color across the whole image.