Using FSR to measure how much water is in my cup.

Motivation:
It happens very often that my cup is overflowing. It is because I usually stare at my computer, work with one hand, and at the same time fill water into my cup with the other hand. With the water-level meter, I won't overfill my cup.

My code:
===

Processing-
===

/*
 * Aithne Sheng-Ying Pao HW4
 * Measure how much water is in the cup
 */
import processing.serial.*;
// Change this to the portname your Arduino board
String portname = "COM8";
Serial port;
String buf="";
int cr = 13;  // ASCII return   == 13
int lf = 10;  // ASCII linefeed == 10

void setup() {
  size(300,300); 
  smooth();
PImage b;  // set background image (please save this image, "cup.jpg" to the same folder of Processing)
b = loadImage("cup.jpg");
background(b);
  noStroke();
  port = new Serial(this, portname, 9600);
}
void draw() {
}

// draw water level subroutine
void drawquad( int r) {
   fill(51,153,255); // water color blue
   quad(70, 300-r, 70, 300, 223, 300, 223, 300-r);
}
// called whenever serial data arrives
void serialEvent(Serial p) {
  int c = port.read();
  if (c != lf && c != cr) {
    buf += char(c);
  }
  if (c == lf) {
    int val = int(buf);
    println("val="+val);
    drawquad(val);
   
    buf = "";
    if (val==0){// erase screen
    PImage b;
    b = loadImage("cup.jpg");
    background (b); 
    }}
}

===

Aduino--
====
/*
 * Resistive Sensor Input
 * Takes the input from a resistive sensor, e.g., FSR or photocell
 * Dims the LED accordingly, and sends the value (0-255) to the serial port
 */
int sensorPin = 0;  // select the input pin for the sensor
int ledPin = 10;    // select the output pin for the LED
int val = 0;        // variable to store the value coming from the sensor
void setup() {
  Serial.begin(9600);
}
void loop() {
  val = analogRead(sensorPin); // read the value from the sensor, 0-1023
  analogWrite(ledPin, val/4);  // analogWrite (dimming the LED) can be between 0-255
  Serial.println(val/4);       // writing the value to the PC via serial connection
  delay(50);                   // rest a little...
}