LineDraw.pde

float gSize=10;//grid size

void setup(){
  size(500, 500);
  background(255);
  fill(0);
  noStroke();
  int x1 = 10;
  int y1 = 10;
  int x2 = 20;
  int y2 = 40;
  int dx = x2 - x1;
  int dy = y2 - y1;
  if(dx > dy){
    for(int x = x1; x <= x2; x++){
      int y = y1 + dy * (x - x1) / dx;
      rect(x*10, y*10, 10, 10);
    }
  }else{
    for(int y = y1; y <= y2; y++){
      int x = x1 + dx * (y - y1) / dy;
      rect(x*10, y*10, 10, 10);
    }
  }
}

void draw(){
  
}