NullPointerException when trying to use a function inside of a class

I'm trying to make a simple game in Processing where you move an object around with changing sprites and a moving parallax background with three layers. I get this error when I run it from home.

java.lang.NullPointerException: Cannot read field "width" because "img" is null
    
at processing.core.PGraphics.image(PGraphics.java:3953)

    at processing.core.PApplet.image(PApplet.java:12499)

    at assignment_3$Background.parallax(assignment_3.java:79)

    at assignment_3.draw(assignment_3.java:33)

    at processing.core.PApplet.handleDraw(PApplet.java:2185)

    at processing.awt.PSurfaceAWT$9.callDraw(PSurfaceAWT.java:1440)

    at processing.core.PSurfaceNone$AnimationThread.run(PSurfaceNone.java:356)

It's probably something to do with calling the arrays but idk. I've tried to see if it's something with the setup inside of each class but I can't figure it out.

assignment_3

Player hero;
Background bg;

int animFrame = 0;
int cameraX = 0;

void setup() {
  size(400, 180);
  frameRate(120);
  hero = new Player(10, 10, 0, 0);
  bg = new Background();

}

void draw() {
  animFrame = (frameCount / 3) % 6;
  bg.parallax(cameraX);
  
 if (keyPressed) {
   hero.acc();
 }
 else {
   hero.stop();
 }
 
 if(hero.x > 300) {
   cameraX += 1;
 }
 hero.step();
 hero.animate(animFrame);
}

Background

class Background {
  
  PImage[] background = new PImage[3];
  int cameraX;
  int world2Screen(int x, int y, int z) {
    return(x - cameraX)/z;
  }
  
void setup() {
  background[0] = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/background_layer_1_sm.png");
  imageDouble(background[0]);
  background[1] = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/background_layer_2_sm.png");
  imageDouble(background[1]);
  background[2] = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/background_layer_3_sm.png");
  imageDouble(background[2]);
}

void imageScale(PImage toScale, float scale){  
  toScale.resize(int(toScale.width*scale),int(toScale.height*scale));
}

void imageDouble(PImage toScale){
  // toScale.resize(int(toScale.width*2),int(toScale.height*2));
  // but better to reuse
  imageScale(toScale,2.0);
}

void parallax(int cam) {
  if(cam == 0) {
    image(background[0], world2Screen(0, 0, 3), 0);
    image(background[0], world2Screen(background[0].width*((cam/background[0].width) + 3),0, 3), 0);
    image(background[1], world2Screen(0, 0, 2), 0);
    image(background[1], world2Screen(background[1].width*((cam/background[1].width) + 3),0, 3), 0);
    image(background[2], world2Screen(0, 0, 1), 0);
    image(background[2], world2Screen(background[2].width*((cam/background[2].width) + 3),0, 3), 0);
}
}
}

Player

class Player {
  
  float x, y, runSpeed, jumpSpeed;
  int animFrame = 0;
  int charW = 56;
  String direction;
  boolean jump;
  
  PImage idlesheetl = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/idle_l.png");
  PImage idlesheetr = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/idle_r.png");
  PImage[] idlel = new PImage[6];
  PImage[] idler = new PImage[6];
  
  PImage runsheetl = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/run_l.png");
  PImage runsheetr = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/run_r.png");
  PImage[] runl = new PImage[8];
  PImage[] runr = new PImage[8];
  
  PImage jumpsheetl = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/jump_l.png");
  PImage jumpsheetr = loadImage("https://ecs.wgtn.ac.nz/foswiki/pub/Courses/CGRA151_2022T2/Assignment3/jump_r.png");
  PImage[] jumpl = new PImage[10];
  PImage[] jumpr = new PImage[10];

Player(float xPos,float yPos,float rSpeed,float jSpeed) {
  x = xPos;
  y = yPos;
  runSpeed = rSpeed;
  jumpSpeed = jSpeed;
  direction = "right";
  jump = false;
}

void setup(){
  for(int i = 0; i < idlel.length; i++) {
    idlel[i] = idlesheetl.get(i*charW, 0, charW, charW);
    idler[i] = idlesheetr.get(i*charW, 0, charW, charW);

  }
  for(int i = 0; i < runl.length; i++) {
    runl[i] = runsheetl.get(i*charW, 0, charW, charW);
    runr[i] = runsheetr.get(i*charW, 0, charW, charW);

  }
  for(int i = 0; i < jumpl.length; i++) {
    jumpl[i] = jumpsheetl.get(i*charW, 0, charW, charW);
    jumpr[i] = jumpsheetr.get(i*charW, 0, charW, charW);
  }
}

void animate(int animFrame) {
  if(jump) {
    if(direction == "right") {
      image(jumpr[animFrame], x, (height - y) - charW);
    }
    else {
      image(jumpl[animFrame], x, (height - y) - charW);
    }
  }
  if(!jump) {
    if(runSpeed == 0 && jumpSpeed == 0) {
      if(direction == "right") {
      image(idler[animFrame], x, (height - y) - charW);
    }
    else {
      image(idlel[animFrame], x, (height - y) - charW);
    }
    }
  }
  if(runSpeed > 0) {
    if(direction == "right") {
    image(runr[animFrame], x, (height - y) - charW);
    }
    else {
      image(runl[animFrame], x, (height - y) - charW);
    }
  }
}

void step() {
  
  if(y < 10) {
    y = 10;
  }
  
  if(y > 150) {
    y = 150;
  }
  
  if(y > 0 && x < width - 60) {
    x  += runSpeed;
  }
  else if (x <= 0) {
    x = 10;
  }
  else {
    x = 315;
  }
  if(y < height) {
    y += jumpSpeed;
  }
}
  

void acc() {

}

void stop() {

}


}