Pencil Code Reference > pen
pen will pick a drawing color
When the turtle moves, it will trace out a line in the pen color.
pen blueviolet
Here are some basic colors that can be used with pen:
| white | yellow | lime | aqua | blue | fuchsia | red | silver |
| gray | olive | green | teal | navy | purple | maroon | black |
For all 140 standard named colors, see the color table.
pen accepts an optional second argument, which is the width of the
pen in pixels. Remember that arguments need to be separated by
a comma.
pen pink, 20
pen accepts an optional third argument, which is the name of
a line-cap style to use.
| line-cap style | pen shape | example |
|---|---|---|
| 'round' (default) | circle | pen coral, 25, 'round' |
| 'square' | square | pen skyblue, 25, 'square' |
| 'butt' | flat brush | pen violet, 25, 'butt' |
Remember to enclose the line cap style in quotes. These line cap values are strings.
Round line caps are the default. They are forgiving and useful for general gometric shapes. Butt line cas are useful when you need a line that is exactly the length that you asked for. Square line caps are useful for lining up rectangular shapes with line ends.
To control the appearance of corners, use the optional fourth argument
of pen, which controls a line-join style to use.
| line-join style | corners | example |
|---|---|---|
| 'round' (default) | rounded | pen coral, 25, 'butt', 'round' |
| 'miter' | sharp | pen skyblue, 25, 'butt', 'miter' |
| 'bevel' | flat | pen violet, 25, 'butt', 'bevel' |
Names of both line-cap styles and line-join styles are taken from the HTML5 Canvas and SVG standards.
When tracing out a colored path with a, the path is continuously drawn with one end at the turtle.
This can sometimes result in overdrawing. For example, if you have a line-cap style like square that extends beyond the line-join shape for a sharp angle, extra pixels can stick out if you draw the path continuously.
This can be solved by using a pen to trace out an invisible path, then using the fill command to draw the whole path at once. With fill, you specify the line drawing options by name:
pen path fd 100 rt 120 fd 100 fill strokeStyle: green lineWidth: 25 lineCap: square
fill can also be used to fill shapes with solid colors using the default fillStyle property.
There is also special "color" called erase that will remove any existing color it passes over.
pen red fd 50 home() pen erase fd 50↑