Processing sketch (Java-like) to display and experiment with various gradient methods

sketch_apr15b.pde

int barWidth=50;
GradientI[] grads=new GradientI[4];

void setup() {
  size(1600, 300);
  colorMode(HSB, 360, 100, 1.0);
  noStroke();
  background(0);
  grads[0]=new LiearGradient();    /*  lin     */
  grads[1]=new LiearGradient(1.1); /*  clip_a  */
  grads[2]=new CirculatGradient(); /*  f(x)    */
  grads[3]=new LiearGradient(1.2); /*  clip_b  */
}

void draw() {
  int start=0;
  int step=height/grads.length;
  for (int gid=0;gid<grads.length;gid++) {
    for (int i=0;i<width;i+=barWidth) {
      fill(30, 100, grads[gid].perentageDark((float)i/(float)width) );
      rect(i, start, barWidth, start+step);
    }
    start+=step;
  }
}

/**
 * Simple linar function, optionally clipped
 */
class LiearGradient implements GradientI {
  float clipping;
  LiearGradient() {
    this(1.0);
  }
  LiearGradient(float clipping) {
    this.clipping=clipping;
  }
  float perentageDark(float percentageAdvanced) {
    return max(0.0,min(1.0, clipping*(percentageAdvanced-(1-1/clipping)/2)));
  }
}

/**
 * Shadow gradient of circular lights
 */
class CirculatGradient implements GradientI {
  float perentageDark(float percentageAdvanced) {
    return (2*sqrt(-(percentageAdvanced-1)*percentageAdvanced)*(2*percentageAdvanced-1)+acos(1-2*percentageAdvanced))/PI;
  }
}

/**
 * Gradient Interface
 */
interface GradientI {
  /**
   * Calculate the mixing factor
   */
  float perentageDark(float percentageAdvanced);
}