colored line

gistfile1.txt

void setup() {
  size(600, 600);  
}

void draw() {
   
  background(255);
  
  PVector a = new PVector(mouseX, mouseY);
  PVector b = new PVector(50, height/2);
  
  float w_a = 50;
  float w_b = 150;
  
  int color_a = color(255,0,0);
  int color_b = color(0,0,255);
  
  for (int y = 0; y < height; y++) {
    for (int x = 0; x < width; x++) {
      PVector v = point_nearest_line(a, b, new PVector(x, y));
      
      if (v == null) continue;
      
      float t = dist(v.x, v.y, a.x, a.y) / dist(a.x, a.y, b.x, b.y);
      t = constrain(t, 0, 1);
      float w = map(t, 0, 1, w_b, w_a);
      
      float dist_to_line = dist(v.x, v.y, x, y); 
      if (dist_to_line <= w) {
        
        float t2 = dist_to_line / w;
        int c = lerpColor(color_a, color_b, t2);
        set(x, y, c);
      }
    }
  }
  
}

public float NEARNESS = 1.0;


public PVector point_nearest_line(PVector v0, PVector v1, PVector p){
  PVector vp = null;
  PVector the_line = PVector.sub(v1, v0);
  float lineMag = the_line.mag();
  lineMag = lineMag * lineMag;
  if (lineMag > 0.0) {
    PVector pv0_line = PVector.sub(p, v0);
    float t = pv0_line.dot(the_line)/lineMag;
    if (t >= 0 && t <= 1){
      vp = new PVector();
      vp.x = the_line.x * t + v0.x;
      vp.y = the_line.y * t + v0.y;
    }
  }
  return vp;
}