PImage spritesheet;
int l, c;
PImage show;
PFont font;
int myFrame;
int myFrameRate=20;
float valeur;
boolean inverse=true;

boolean firstMousePress = false;
HScrollbar hs; 

void setup() {
  size(500, 300);
  frameRate(myFrameRate);
  l=4;
  c=4;
  spritesheet=loadImage("explosions.png");
  font=createFont("whitrabt.ttf", 32);
  textFont(font);


  hs = new HScrollbar(20, height-20, width-40, 16, 1);
}

void draw() {
  background(0);
  show = exportImage(spritesheet, 4, 4, l, c);
  image(show, 350, 50);
  stroke(255);
  fill(255);
  myFrame=c+(l-1)*4;
  text(myFrame, 350, 200);
  fill(color(0, 0, 255));
  stroke(color(0, 0, 255));
  text(int(myFrameRate)+" images/s", width/2+30, height-40);

  //show.save("data/explode"+myFrame+".png");
  //if (myFrame==16) exit();

  if (inverse) {
    c--;
    if (c==0) {
      c=4;
      l--;
      if (l==0) {
        l=1; 
        c=1;
        inverse=false;
      }
    }
  } else {
    c++;
    if (c==5) {
      c=1;
      l++;
      if (l==5) {
        inverse=true;
        l=4; 
        c=4;
      }
    }
  }


    hs.update();
    hs.display();
    myFrameRate=int(map(hs.getPos(), 0, hs.swidth, 1, 50));
    frameRate(myFrameRate);
}

PImage exportImage(PImage spritesheet, int nbLignes, int nbColonnes, int ligne, int colonne) {
  image(spritesheet, 0, 0);
  stroke(255);
  noFill();
  rect(0, 0, spritesheet.width, spritesheet.height);
  int largeurExport=spritesheet.width/nbColonnes;
  int hauteurExport=spritesheet.height/nbLignes;
  rect(largeurExport*(colonne-1), hauteurExport*(ligne-1), largeurExport, hauteurExport);
  return spritesheet.get(largeurExport*(colonne-1), hauteurExport*(ligne-1), largeurExport, hauteurExport);
}