int x = max(0, width);
int y = max(0, height);
PImage a,b,c,d;
float mydist;
float a_alpha;
float b_alpha;
float c_alpha;
float d_alpha;


void setup() {
  size(500,500);
  background(255,0);
  smooth(); 
  a = loadImage("logo1.png");
  b = loadImage("logo2.png");
  c = loadImage("logo3.png");
  d = loadImage("logo4.png");

}

void draw(){
  background(255,0);
  mydist = dist(height/2,width/2,mouseX,mouseY);  
  smooth();
  frameRate(30);

  //upper left
  if(mouseX < 250 && mouseY < 250){
    smooth();
    a_alpha = mydist;

    imageMode(CENTER);
    //image(a,height/2,width/2);

  }
  //upper right
  if(mouseX > 250 && mouseY < 250){
    smooth();
    c_alpha = mydist;
    //tint(255, 255, 255, mydist); 
    imageMode(CENTER);
    //image(c,height/2,width/2);

  }
  //lower right
  if(mouseX > 250 && mouseY > 250){
    smooth();
    d_alpha = mydist;
    //tint(255, 255, 255, mydist); 
    imageMode(CENTER);
    //image(d,height/2,width/2);

  }
  //lower left
  if(mouseX < 250 && mouseY > 250){
    smooth();
    b_alpha = mydist;
    //tint(255, 255, 255, mydist); 
    imageMode(CENTER);
    //image(b,height/2,width/2);

  }
  //images here for alpha to work
  tint(255, 255, 255, a_alpha);
  image(a,height/2,width/2);
  tint(255, 255, 255, c_alpha);
  image(c,height/2,width/2);
  tint(255, 255, 255, d_alpha);
  image(d,height/2,width/2);
  tint(255, 255, 255, b_alpha);
  image(b,height/2,width/2);
}

void mouseMoved() {
  x = mouseX/2;
  y = mouseY/2;

}