Revision Date: 6 September 2024

Line/Curve Tool
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This tool is used to draw lines and curves. These two abilities are grouped into a single tool because a line is actually a perfectly straight curve. In other words, this tool always draws curves, where a straight line is a subset involving no actual curvature.

Drawing a line is straightforward: click where the line begins and drag the mouse pointer to the end point. Releasing the mouse button ends the "drawing" phase.

Note

Using the Left Mouse button renders the line with the Primary color. Using the Right Mouse Button renders the line in the Secondary color.

When the drawing phase is ended, four control nubs appear on the line and the four-way move icon appears just off the end point of the line.

The Control Nubs and Move icon pulsate to make them easier to distinguish.

If a single, straight line is desired, press the Enter key or click the Finish button in the Tool Bar to commit the line to the canvas. Drawing elsewhere on the canvas finishes any previous line and starts a new one.

Tip

Holding down the Shift key before releasing the mouse button constrains the line to angles that are multiples of 15 degrees, e.g. 0°, 15°, 30°, 45° 60° and so on.

Tip

Holding down the Alt key before releasing the mouse button reflects the line about it's center. This key modifier makes it possible to draw a line or curve centered on the point where the dragging operation started.

If a curve is desired, drag the control nubs to a new location by clicking and dragging.

Moving a Line/Curve

Before a Line/Curve is committed to the canvas, it can be moved anywhere on the canvas. Click and drag the pulsing Move icon (four-arrows-in-a-square) using the Left Mouse Button to reposition the Line/Curve.

The keyboard arrow keys ↑ ← ↓ → can also be used to move a Line/Curve. A single key press moves the object by one pixel in the direction of the arrow. Simultaneously holding the Ctrl key moves the object by 10 pixels per arrow key press.

Rotating a Line/Curve

Before a Line/Curve is committed to the canvas, it can be rotated about its geometric center.

Rotate the Line/Curve about the center using the Right Mouse Button. Click and drag to rotate. As a visual guide that rotation is possible, the mouse pointer will turn into a double headed arrow (see diagram).

Rotate or Move a Line/Curve — Rotate Cursor

If the Shift key is held down while rotating the angle of rotation is snapped to 15 degree increments.

The keyboard arrow keys ↑ ← ↓ → can also be used to rotate a Line/Curve while the Right Mouse Button is held down.

Committing a Line/Curve to the canvas

Commit a Line/Curve to the active layer and exit editing mode using any one of these methods…

Press the Enter key
Click outside of the bounding box of the current Line/Curve.
Click Finish in the Tool Bar
Draw a new Line/Curve.

Curve Types

There are three icons in the Tool Bar for changing between Straight, Cubic Spline and Bézier curves.

If the Left icon (Straight) is used, the line will always display straight line segments between the control nubs.

If the middle icon (Spline) is selected, the line will be curved using cubic spline interpolation. This means the line will always continue through each of the Control Nubs, even if the nubs are relocated or dragged off canvas. When a nub is moved, the curve will be redrawn so that it always goes through the center of each Control Nub.

If the Right icon is selected (Bézier), a Bézier curve results. With this curve type, the curve will extend from the first or origin Control Nub to the last or destination Control Nub. The second and third Control Nubs modify the curve along its path. The curve will not necessarily touch either the second or third Control Nub. Some types of Bézier curves cannot be drawn using the Cubic Spline type.

Tip

Switch between curve types by toggling between the Curve Icons in the Tool Bar. The curve will be reinterpreted based on the curve type and current location of the Control Nubs.

Brush Width, Line Style and Fill

Lines and curves are subject to the Brush settings in the Tool Bar. Brush Width, Line Styles & Fill Type are all configurable.

The Line/Curve can have different start cap, dash style, and end cap. The start- and end-caps can be flat (normal), one of two arrow head types, or rounded. The dash style can be either solid or a combination of dashes and dots.

Using Brush Width & Line Styles lines like these can be drawn:

Lines and curves can be rendered using a Fill Type as specified in the Tool Bar. This feature allows the line/curve to be filled with one of numerous patterns rather than a solid color.

Fills utilizing a fill style will make use of both the Primary and Secondary colors.

Antialiasing

There are two antialiasing modes associated with the Line/Curve tool.

These settings determine whether the line is rendered as solid pixels or smoothed with interpolated shades spreading into neighboring pixels.

When Antialiasing is selected, lines will appear slightly thicker and smoother (upper example). Internally, Paint.NET uses x2 or x4 super sampling to improve the quality of antialiasing.

When Aliased is selected, lines are rendered only as solid pixels. These will appear more jagged and thinner (lower example).

Antialiasing can be switched on or off via the Tool Bar when the Text tool is active.

Blend Modes

Lines and curves can be applied using a Blend Mode selected from the Tool Bar. The line/curve will be applied in accordance with the other parameters then reinterpreted as if the pixels were on their own layer with the layer blend mode set.

Line/Curve Tool O once