multi page PDF. / getting blank page every 5 pages

Wrote this little program that takes a master image (local), splits it into pages (because it's big), and reproduces it with tiles (taken from Flikr) based on averaged colors. On the back of each sheet is a page number, so we know ho to put them back order. All works great! very pleased! But for some reason, i get a blank page every 5 pages... why? Master image size is currently 4771 x 3181px

Also, this code probably needs some optimization, but that's another topic.

/**
 * This code is copyright (c) Mathias Markl 2016 (the imageLoader part)
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <http://www.gnu.org/licenses/>.
 */

import at.mukprojects.imageloader.*;
import at.mukprojects.imageloader.flickr.*;
import at.mukprojects.imageloader.image.*;

import processing.pdf.*;


PGraphicsPDF pdf;


ImageLoader loader;
ImageList list;
Image img;

String apiKey = "xxxx";
String apiSecret = "xxxx";

PImage master = new PImage();
PImage cover = new PImage();

int maxImages = 50;
int detail = 50;
int loaderOn = 1;
int extra;

PImage[] myImages = new PImage[50];

StringList imageSorter = new StringList(0);
int c=0;
int i=0;
int j =0;
int k =0;
int n =0;
int o=0;

//// Image Thingies

PImage baseImage;
int baseIndex=5;
int maxHeight=900;
int maxWidth=900;

int rounderY;
int rounderX;

IntList rTile = new IntList(0);
IntList gTile = new IntList(0);
IntList bTile = new IntList(0);
int rBase;
int gBase;
int bBase;
IntList cRVar = new IntList(0);
IntList cGVar = new IntList(0);
IntList cBVar = new IntList(0);
IntList cVar = new IntList(0);
IntList targetArray = new IntList(0);

int target;
int page=1;
PFont noPage;

void setup() {
  size(1000, 1000);

  loader = new FlickrLoader(this, apiKey, apiSecret);
  list = loader.start("sunset", false, 60*1000);

  master=loadImage("master.jpg");

  pdf = (PGraphicsPDF)beginRecord(PDF, "Lines.pdf");

  frameRate (60);
}

void draw() {


  if (loaderOn==1) {
    println("retrieved "+list.size()+" photos");
    //println(list.getIds());


    // Remove Duplicates

    if (list.size()==maxImages) {
      for (int b=0; b<maxImages; b++) {
        if (imageSorter.size()==0) {
          img = list.getImage(k);
          imageSorter.append(img.getImgUrl());
          k++;
        } else if (imageSorter.size()>0) {
          img = list.getImage(k);
          if (imageSorter.get(imageSorter.size()-1)==img.getImgUrl()) {
            k++;
          } else {
            imageSorter.append(img.getImgUrl());
            k++;
          }
        }
      }


      // Resizing all the funzies!

      println("LOADING IMAGES INTO PIMAGE ARRAY AND RESIZING");

      for (int i=0; i<imageSorter.size(); i++) {
        myImages[i]=loadImage(imageSorter.get(i), "jpg");
        myImages[i].resize(detail, detail);
      }


      // Tile Pixel Averaging Baby Boy

      println("LOADING AND AVERAGING TILE PIXEL COLORS");

      for (int i=0; i<imageSorter.size(); i++) {
        myImages[i].loadPixels();
        color r = 0, g = 0, b = 0;

        for (color c : myImages[i].pixels) {
          r += c >> 020 & 0xFF;
          g += c >> 010 & 0xFF;
          b += c        & 0xFF;
        }

        r /= myImages[i].pixels.length;
        g /= myImages[i].pixels.length;
        b /= myImages[i].pixels.length;

        rTile.append(r);
        gTile.append(g);
        bTile.append(b);
      }
      println("DONE");
      loader.stop();
      list=null;
      loaderOn=0;
    }
  }



  // Fonctions répetées à chaques page //


  if (loaderOn==0) {

    // Découpage du master en pages (imageBase)

    for (int v=0; v<master.height; v+=height) {
      for (int w=0; w<master.width; w+=width) {


        baseImage=master.get(v, w, width, height);


        // Découpage de la page en détails




        for (i=0; i<baseImage.width; i+=detail) {
          for (j=0; j<baseImage.height; j+=detail) {

            println("LOADING AND AVERAGING DETAIL COLORS"+" "+"DETAIL NO"+" "+(i+j));

            PImage newImg = baseImage.get(i, j, detail, detail);

            // Analyze de la couleur de chaque détail


            newImg.loadPixels();

            color rBase = 0, gBase = 0, bBase = 0;

            for (color c : newImg.pixels) {
              rBase += c >> 020 & 0xFF;
              gBase += c >> 010 & 0xFF;
              bBase += c        & 0xFF;
            }

            rBase /= newImg.pixels.length;
            gBase /= newImg.pixels.length;
            bBase /= newImg.pixels.length;

            if ((rBase+gBase+bBase)==0) {
              fill(255);
              noStroke();
              rect(i, j, detail, detail);
            } else {

              // Calcule de détail le plus près de l'image de base

              println("ANALYSING TILE COLOR PROXIMITY");


              for (k=0; k<maxImages; k++) {
                cRVar.append(abs(rBase-rTile.get(k)));

                cGVar.append(abs(gBase-gTile.get(k)));

                cBVar.append(abs(bBase-bTile.get(k)));

                cVar.append(cRVar.get(k)+cGVar.get(k)+cBVar.get(k));

                println("APPROX TILE NO"+k );
              }

              target = cVar.index(cVar.min());
              println("MATHCHING TILE="+target);
              image(myImages[target], i, j);
              println("CLEARING ALL VARIABLES");

              c=o;

              k=0;
              n=o;
              o=0;

              cRVar.clear();
              cGVar.clear();
              cBVar.clear();
              cVar.clear();

              println("PRINTING TILE "+(i+j));
            }
          }
        }
        i=0;
        j=0;
        //baseImage.resize(0, 250);
        //image(baseImage, width-baseImage.width, height-baseImage.height);

        pdf.nextPage();

        PFont noPage = createFont("Helvetica", 100, true);
        textFont(noPage, 500);
        fill(225);
        textAlign(CENTER, CENTER);
        text(page, width/2, height/2);

        pdf.nextPage();
        page++;
      }
    }
    cover=master;

    if (cover.width>cover.height) {
      cover.resize(width-200, 0);
      rounderY = (cover.height%20);
      cover.resize(width-200, cover.height-rounderY);
    } else if (cover.width<cover.height) {
      cover.resize(0, height-200);
      rounderX = (cover.width%20);
      cover.resize(cover.width-rounderX, height-200);
    }
    PFont noPage = createFont("Helvetica", 100, true);
    textAlign(CENTER, CENTER);
    textFont(noPage, 20);
    text("Mosaïc Poster Maker", width/2, ((height-cover.height)/2)-100);
    text("Jonathan Mélançon", width/2, ((height+cover.height)/2)+100);
    imageMode(CENTER);
    image(cover, width/2, height/2);

    endRecord();
    println("PDF DONE!");
    exit();
  }
}