App Lab Documentation

penRGB

Category:Turtle

Explore the 256^3 possible colors you can choose from using the three required numeric parameters. The fourth optional parameter is the opacity of the color, a percentage between 0 and 1. The default pen color is black, penRGB(0,0,0), and the pen is by default in the down (drawing) position.

Examples

Basic Example

// Sets the color of the line the turtle draws behind it to orange.
penRGB(255,165,0);   
moveForward();

Example: Flag of France

You can look up official RGB values for most country flags on Wikipedia.

// Flag of France - You can look up official RGB values for most country flags on Wikipedia.
penWidth(150);
penRGB(0,85,164);
penUp();
moveTo(0,75);
turnTo(90);
penDown();
moveForward(350);

penRGB(255,255,255);
penUp();
moveTo(0,225);
turnTo(90);
penDown();
moveForward(350);

penRGB(239,65,53);
penUp();
moveTo(0,375);
turnTo(90);
penDown();
moveForward(350);

Example: Random Art

Draw random lines in random colors.

// Draw random lines in random colors.
button("ChangeIt", "Click Me");
onEvent("ChangeIt", "click", function() {
  penRGB(randomNumber(0,255),randomNumber(0,255),randomNumber(0,255), randomNumber(0,100)/100);
  penWidth(randomNumber(10,50));
  moveTo(randomNumber(0,320),randomNumber(0,450));
});

Example: User Color Choice Dots

Prompts the user for r, g, b values and draws a random size dot at a random location. A console warning is generated if the user enters an invalid r or g or b value. Negative values are set to 0 and values greater than 255 are set to 255.

// Prompts the user for r, g, b values and draws a random size dot at a random location. 
// A console warning is generated if the user enters an invalid r or g or b value. 
// Negative values are set to 0 and values greater than 255 are set to 255.
textLabel("RedLabel", "Red (0-255)");
textInput("RedID", "0");
textLabel("GreenLabel", "Green (0-255)");
textInput("GreenID", "0");
textLabel("BlueLabel", "Blue (0-255)");
textInput("BlueID", "0");
onEvent("RedID", "change", function() {
  penRGB(getText("RedID"), getText("BlueID"), getText("GreenID"));
  penUp();
  moveTo(randomNumber(0,320),randomNumber(0,450));
  dot(randomNumber(10,50));
});
onEvent("GreenID", "change", function() {
  penRGB(getText("RedID"), getText("BlueID"), getText("GreenID"));
  penUp();
  moveTo(randomNumber(0,320),randomNumber(0,450));
  dot(randomNumber(10,50));
});
onEvent("BlueID", "change", function() {
  penRGB(getText("RedID"), getText("BlueID"), getText("GreenID"));
  penUp();
  moveTo(randomNumber(0,320),randomNumber(0,450));
  dot(randomNumber(10,50));
});

Syntax

penRGB(r, g, b, a);

Parameters

Name	Type	Description
r	Number	The amount of red (0-255) in the pen used by the turtle for drawing lines and dots.
g	number	The amount of green (0-255) in the pen used by the turtle for drawing lines and dots.
b	number	The amount of blue (0-255) in the pen used by the turtle for drawing lines and dots.
a	number	The opacity, a number between 0.0 (fully transparent) and 1.0 (fully opaque), of the color used by the turtle for drawing lines and dots. Default is 1.0.

Returns

No return value. Modifies turtle drawing only.

Tips

penUp() causes no line to be drawn.
Turtle drawing commands are not effected by the show() and hide() commands, which control if the turtle icon is displayed or not.
Recall Unit 1 lessons about rgb color values.
To choose a color by name or hex value use penColor(color) which takes one string parameter instead of numeric parameters.

Found a bug in the documentation? Let us know at support@code.org.