ValueNoise

/*
Adapted from C source code found at https://www.reddit.com/r/gamedev/comments/3g89el/portable_procedural_land_generation/
// The C source was licensed under http://creativecommons.org/licenses/by/4.0/
// and this Java version is made available under the same license.
edit: above C source was released into the public domain, and this source file is made available under the same terms, without warranty for any use or purpose.

Java version by Charles Griffiths, August 10, 2015
This version refers to classes in libgdx (com.badlogic.gdx).
*/

import java.io.BufferedWriter;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.Random;

import com.badlogic.gdx.graphics.Pixmap;
import com.badlogic.gdx.graphics.Pixmap.Format;



public class ValueNoise
{
protected Random r;
public final int width, height;
private int size;
private int elevation[][];


  public ValueNoise( int width, int height )
  {
  int i, max = Math.max( width, height );

    this.width = width;
    this.height = height;
    for (i=1; Math.pow( 2, i )+1 <= max; i++);
    size = (int) Math.pow( 2, i );
  }


  public int getElevation( int x, int y )
  {
    if (x >= 0 && x < width && y >= 0 && y < height)
      return elevation[x][y];

    return 0;
  }


  public void generate()
  {
    generate( System.currentTimeMillis() );
  }

  public void generate( long seed )
  {
  int noise[][] = getArray();

    r = new Random( seed );
    elevation = getArray();

    for (int a=1, t=2; t<=size/4; a*=2, t*=2)
      octave( noise, a, t );
  }


  private int[][] getArray()
  {
  int ia[][] = new int[size+1][size+1];

    for (int i=0; i<=size; i++)
      Arrays.fill( ia[i], 0 );

    return ia;
  }


  protected void octave( int noise[][], int a, int t )
  {
    for (int i=0; i<size; i+=t)
      for (int j=0; j<size; j+=t)
        noise[i][j] = r.nextInt( a ) - a/2;

    for (int i=0; i<size; i+=t)
      for (int j=0; j<size; j+=t)
        binterp( noise, i, j, t );

    for (int i=0; i<=size; i++)
      for (int j=0; j<=size; j++)
        elevation[i][j] += noise[i][j];
  }


  protected void binterp( int noise[][], int i0, int j0, int t )
  {
  int a = t*t;

    for (int i=i0; i<=i0+t; i++)
      for (int j=j0; j<=j0+t; j++)
      {
      int b = (int) (noise[  i0][  j0] * (t-j+j0) * (t-i+i0));
      int c = (int) (noise[  i0][t+j0] * (  j-j0) * (t-i+i0));
      int d = (int) (noise[t+i0][  j0] * (t-j+j0) * (  i-i0));
      int e = (int) (noise[t+i0][t+j0] * (  j-j0) * (  i-i0));

        noise[i][j]=(b+c+d+e)/a;
    }
  }


  public void save( String filename )
  {
    try
    {
    FileOutputStream fos = new FileOutputStream( filename );

      writeAscii( fos );
      fos.close();
    }
    catch (FileNotFoundException e)
    {
      e.printStackTrace();
    }
    catch (IOException e)
    {
      e.printStackTrace();
    }
  }


  private void writeAscii( OutputStream os ) throws IOException
  {
  BufferedWriter bw = new BufferedWriter( new OutputStreamWriter( os ));

    for (int i=0; i<height; i++)
    {
    StringBuffer sb = new StringBuffer();

      for (int j=0; j<width; j++)
      {
        if (j > 0)
          sb.append( "\t" );
        sb.append( elevation[i][j] );
      }
      sb.append( System.lineSeparator() );

      bw.write( sb.toString() );
    }

    bw.flush();
  }


  public Pixmap getPixmap()
  {
  Pixmap p = new Pixmap( width, height, Format.RGB888 );
  int max = 0, min = 0;

    for (int i=0; i<height; i++)
      for (int j=0; j<width; j++)
      {
      int z = elevation[i][j];

        if (z > max)
          max = z;
        else if (z < min)
          min = z;
      }

    for (int i=0; i<height; i++)
      for (int j=0; j<width; j++)
      {
      float value = (float)(elevation[i][j] - min) / (max-min+1);

        // greyscale
        p.setColor( value, value, value, 1 );
        p.drawPixel( j, i );
      }

    return p;
  }
}