To represent some color, just declare an object of the ofColor class.

ofColor color;

To initialize the color, set its components.

color.r = 0.0;
color.g = 128.0;
color.b = 255.0;

Or, equivalently, use the constructor.

color = ofColor( 0.0, 128.0, 255.0 );

You can use color as an argument in the functions ofSetColor() and ofBackground(). For example, ofSetColor( color ) and ofBackground( color ).

openFrameworks has a number of predefined colors, including white, gray, black, red, green, blue, cyan, magenta, and yellow. See the full list of colors in the libs/openFrameworks/types/ofColors.h file. To use the predefined colors, add the ofColor:: prefix before these names. For example, ofSetColor( ofColor::yellow ) sets the current drawing color to yellow.

You can modify the color using the following functions:

Let's consider an example that demonstrates color modifications.

In this example, we will modify the red color by changing its brightness, saturation, and hue through the whole range and draw three resultant stripes.

This example project is based on the openFrameworks emptyExample project. Fill the body of the testApp::draw() function with the following code:

ofBackground( 255, 255, 255 );    //Set white background

//Changing brightness
for ( int i=0; i<256; i++ ) {
  ofColor color = ofColor::red;  //Get red color
  color.setBrightness( i );      //Modify brightness
  ofSetColor( color );
  ofLine( i, 0, i, 50 );    
}

//Changing saturation
for ( int i=0; i<256; i++ ) {
  ofColor color = ofColor::red;  //Get red color
  color.setSaturation( i );      //Modify saturation
  ofSetColor( color );
  ofLine( i, 80, i, 130 );
}

//Changing hue
for ( int i=0; i<256; i++ ) {
  ofColor color = ofColor::red;  //Get red color
  color.setHue( i );             //Modify hue
  ofSetColor( color );
  ofLine( i, 160, i, 210 );
}

Run the project and you will see three stripes consisting of the red color with changed brightness, saturation, and hue.

As you can see, changing brightness, saturation, and hue is similar to the color-corrections methods used in photo editors like Adobe Photoshop and Gimp. From a designer's point of view, this is a more powerful method for controlling colors as compared to directly specifying the red, green, and blue color components.

Now we will consider how to perform drawings with uncleared background, which can be useful in many creative coding projects related to 2D graphics.