Draw random black-and-white forest

Question

Your task is to write program which will draw 800x600 black-and-white image with something resembling a forest.

Like this (it is dithered photo):

Rules

• You are disallowed to use any existing images - you should generate image purely algorithmically
• Use only 2 colors - black and white (no grayscale)
• Each time program runs image should be new - random every time
• One tree is not a forest (let say 5 trees minumum)
• Special libraries for drawing trees/forests are disallowed
• Answer with most votes wins

Answer 1

C: 3863 1144 1023 999 942 927

The original solution saves 2 pnm files per run (one with g appended, before dithering). Because the dithering wasn't beautiful for the first few lines, there is a hack in place to render more lines than needed, and crop during output.

The golfed solution has a simpler dithering and saves only the dithered image. (no warnings with gcc -std=c11 -pedantic -Wall -Wextra)

Example images from 3 original program runs and one run of the golfed version (last image):

Golfed version

  #include <math.h>
  #include <time.h>
  #include <stdlib.h>
  #include <stdio.h>
  #define D float
  #define R rand()/RAND_MAX
  #define Z(a,b,c) if(10.*R>a)T(h,s,j+b+c*R,g);
  #define U a[y][x]
  #define V e[y+1][x
  #define F(x) for(i=0;i<x;++i)
  int i,x,y,W=800,H=600;unsigned char a[600][800],c;D e[601][802],r,b,k,l,m,n,f,w,
  d,q=.01;void T(D h,D s,D j,D g){r=b=0;do{j+=.04*R-.02;h+=sin(j)*q;s+=cos(j)*q;b
  +=q;g+=q;f=525/d;r=.25-g/44;m=w*f+s*f+W/2;n=2*f-h*f+H/2;f*=r;for(y=n-f-2;y<n+f+2
  ;++y)if(y>=0&&y<H)for(x=m-f-2;x<m+f+2;++x)if(x>=0&&x<W)if(k=m-x,l=n-y,f>sqrt(k*k
  +l*l))if(U>d*3)U=d*3;}while(b<10*r+12*r*R&&r>q);if(r>q){Z(2,.26,.35)Z(2,-.26,-
  .35)Z(7,-.05,.1)}}int main(){FILE* o=fopen("i","wb");srand(time(0));F(W*H){y=i/W
  ;a[y][i%W]=(y<313)?255:6e3/(2*y-H);}F(200)w=1e2*R-60,d=80.*R+5,T(0,0,1.58,0);F(W
  *H){x=i%W;y=i/W;k=U+e[y][x+1];U=-(k>0);l=(k-U)*.1;e[y][x+2]+=l*4;V]+=l*2;V+1]+=l
  *3;V+2]+=l;}fprintf(o,"P5 800 600 255 ");fwrite(a,1,W*H,o);}

Original version

  #include <math.h>
  #include <stdio.h>
  #include <stdlib.h>

  #define W 800
  #define H 600
  #define SPEED 0.01
  #define HEIGHT 11.0

  #define R(m) ((double)(m) * rand() / RAND_MAX)
  #define RAD(deg) ((deg) / 180.0 * M_PI)
  #define LIMIT(x, min, max) ((x) < (min) ? (min) : (x) > (max) ? (max) : (x))

  void shade(void);
  void growTree(double dist, double side, double h, double s, double alpha, double grown);
  void plot(double dist, double side, double h, double s, double alpha, double diam);
  void dither(void);
  void writeImg(int dither);

  unsigned char img[H+10][W];
  double err[H+10+2][W+4];
  long tim;

  int main(void)
  {
     int i;
     tim = time(0);
     srand(tim);
     shade();
     for(i = 0; i < 200; ++i)
     {
        growTree(5 + R(75), -60 + R(120), 0.0, 0.0, RAD(90), 0.0);
     }
     writeImg(0);
     dither();
     writeImg(1);
  }

  void shade(void)
  {
     int y;
     for(y = -10; y < H; ++y)
     {
        double dist = H * 3.5 / (2 * y - H);
        unsigned char color = dist / 80 * 255;
        if(y <= H / 2 || dist > 80) color = 255;
        memset(img[y+10], color, W);
     }
  }

  void growTree(double dist, double side, double h, double s, double alpha, double grown)
  {
     double diam, branchLength = 0.0;

     do
     {
        alpha += R(RAD(3)) - RAD(1.5);
        h += sin(alpha) * SPEED;
        s += cos(alpha) * SPEED;
        branchLength += SPEED;
        grown += SPEED;
        diam = (1.0 - grown / HEIGHT) * 0.5;
        plot(dist, side, h, s, alpha, diam);
     } while(branchLength < 5 * diam + R(6 * diam) && diam > 0.02);

     if(diam > 0.02)
     {
        int br = 0;

        if(R(10) > 2) br++,growTree(dist, side, h, s, alpha + RAD(15) + R(RAD(20)), grown);
        if(R(10) > 2) br++,growTree(dist, side, h, s, alpha - RAD(15) - R(RAD(20)), grown);
        if(R(10) < 2 || br == 0) growTree(dist, side, h, s, alpha - RAD(2.5) + R(RAD(5)), grown);
     }
  }

  void plot(double dist, double side, double h, double s, double alpha, double diam)
  {
     int x, y;
     double scale = H / 4.0 * 3.5 / dist;
     double x0 = side * scale + s * scale + W / 2.0;
     double y0 = H / 2.0 + 2.0 * scale - h * scale;
     diam *= scale;
     h *= scale;
     s *= scale;
     for(y = y0 - diam / 2 - 2; y < y0 + diam / 2 + 2; ++y)
     {
        if(y < -10 || y >= H) continue;
        for(x = x0 - diam / 2 - 2; x < x0 + diam / 2 + 2; ++x)
        {
           double dx, dy, d;
           if(x < 0 || x >= W) continue;
           dx = x0 - x;
           dy = y0 - y;
           d = diam / 2 - sqrt(dx * dx + dy * dy) + 0.5;
           if(d > 0)
           {
              unsigned char color = dist / 80 * 255;
              if(img[y+10][x] > color) img[y+10][x] = color;
           }
        }
     }
  }

  void dither(void)
  {
     int x0, x, y;
     for(y = -10; y < H; ++y)
     {
        for(x0 = 0; x0 < W; ++x0)
        {
           double error, oldpixel;
           unsigned char newpixel;
           if(y%2) x = W - 1 - x0;
           else x = x0;
           oldpixel = img[y+10][x] + err[y+10][x+2];
           newpixel = oldpixel > 127 ? 255 : 0;
           img[y+10][x] = newpixel;
           error = oldpixel - newpixel;
           err[y+10  ][x+1+2*(1-y%2)] += error * 7 / 48;
           err[y+10  ][x+4*(1-y%2)] += error * 5 / 48;
           err[y+10+1][x  ] += error * 3 / 48;
           err[y+10+1][x+1] += error * 5 / 48;
           err[y+10+1][x+2] += error * 7 / 48;
           err[y+10+1][x+3] += error * 5 / 48;
           err[y+10+1][x+4] += error * 3 / 48;
           err[y+10+2][x  ] += error * 1 / 48;
           err[y+10+2][x+1] += error * 3 / 48;
           err[y+10+2][x+2] += error * 5 / 48;
           err[y+10+2][x+3] += error * 3 / 48;
           err[y+10+2][x+4] += error * 1 / 48;
        }
     }
  }

  void writeImg(int dither)
  {
     FILE* fp;
     char buffer[32];
     sprintf(buffer, "%ld%s.pnm", tim, dither ? "" : "g");
     fp = fopen(buffer, "wb");
     fprintf(fp, "P5\n%d %d\n255\n", W, H);
     fwrite(&img[10][0], 1, W * H, fp);
     fclose(fp);
  }

Answer 2

Java Jungle

(954 golfed)

Full of deep, twisting undergrowth, this is a forest not easily traversed.

It's basically a fractal random walk with slowly shrinking, twisty vines. I draw 75 of them, gradually changing from white in the back to black up front. Then I dither the whole thing, shamelessly adapting Averroes' code here for that.

Golfed: _{(Just because others decided to)}

import java.awt.*;import java.awt.image.*;import java.util.*;class P{static Random rand=new Random();public static void main(String[]a){float c=255;int i,j;Random rand=new Random();final BufferedImage m=new BufferedImage(800,600,BufferedImage.TYPE_INT_RGB);Graphics g=m.getGraphics();for(i=0;i++<75;g.setColor(new Color((int)c,(int)c,(int)c)),b(g,rand.nextInt(800),599,25+(rand.nextInt(21-10)),rand.nextInt(7)-3),c-=3.4);for(i=0;i<800;i++)for(j=0;j<600;j++)if(((m.getRGB(i,j)>>>16)&0xFF)/255d<rand.nextFloat()*.7+.05)m.setRGB(i,j,0);else m.setRGB(i,j,0xFFFFFF);new Frame(){public void paint(Graphics g){setSize(800,600);g.drawImage(m,0,0,null);}}.show();}static void b(Graphics g,float x,float y,float s,float a){if(s>1){g.fillOval((int)(x-s/2),(int)(y-s/2),(int)s,(int)s);s-=0.1;float n,t,u;for(int i=0,c=rand.nextInt(50)<1?2:1;i++<c;n=a+rand.nextFloat()-0.5f,n=n<-15?-15:n>15?15:n,t=x+s/2*(float)Math.cos(n),u=y-s/2*(float)Math.sin(n),b(g,t,u,s,n));}}}

Sane original code:

import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.swing.JFrame;

public class Paint {

    static int minSize = 1;
    static int startSize = 25;
    static double shrink = 0.1;
    static int branch = 50;
    static int treeCount = 75;
    
    static Random rand = new Random();
    static BufferedImage img;
    
    public static void main(String[] args) {
        img = new BufferedImage(800,600,BufferedImage.TYPE_INT_ARGB);
        forest(img);
        dither(img);
        new JFrame() {
            public void paint(Graphics g) {
                setSize(800,600);
                g.drawImage(img,0,0,null);
            }
        }.show();
    }
    
    static void forest(BufferedImage img){
        Graphics g = img.getGraphics();
        for(int i=0;i<treeCount;i++){
            int c = 255-(int)((double)i/treeCount*256);
            g.setColor(new Color(c,c,c));
            tree(g,rand.nextInt(800), 599, startSize+(rand.nextInt(21-10)), rand.nextInt(7)-3);
        }
    }
    
    static void tree(Graphics g, double x, double y, double scale, double angle){
        if(scale < minSize)
            return;
        g.fillOval((int)(x-scale/2), (int)(y-scale/2), (int)scale, (int)scale);
        scale -= shrink;
        int count = rand.nextInt(branch)==0?2:1;
        for(int i=0;i<count;i++){
            double newAngle = angle + rand.nextDouble()-0.5;
            if(newAngle < -15) newAngle = -15;
            if(newAngle > 15) newAngle = 15;
            double nx = x + (scale/2)*Math.cos(newAngle);
            double ny = y - (scale/2)*Math.sin(newAngle);
            tree(g, nx, ny, scale, newAngle);
        }
    }
    
    static void dither(BufferedImage img) {
        for (int i=0;i<800;i++)
            for (int j=0;j<600;j++) {
                double lum = ((img.getRGB(i, j) >>> 16) & 0xFF) / 255d;
                if (lum <= threshold[rand.nextInt(threshold.length)]-0.2)
                    img.setRGB(i, j, 0xFF000000);
                else
                    img.setRGB(i, j, 0xFFFFFFFF);
            }
    }
    
    static double[] threshold = { 0.25, 0.26, 0.27, 0.28, 0.29, 0.3, 0.31,
            0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4, 0.41, 0.42,
            0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, 0.51, 0.52, 0.53,
            0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6, 0.61, 0.62, 0.63, 0.64,
            0.65, 0.66, 0.67, 0.68, 0.69 };

}

One more? Okay! This one has the dithering tuned down a bit, so the blacks in front are much flatter.

Unfortunately, the dither doesn't show the fine details of the vine layers. Here's a greyscale version, just for comparison:

Answer 3

Javascript + HTML - not golfed

A javascript porting of the algorithm of @Manuel Kansten - it's amazing how good these trees look.

Just to do something different, I draw the image in color, then dither to b/w at the last step.

I don't know why, but my forest is less dark and less frightening respect to Manuel's.

Test with JSfiddle or run the new Snippet below. That's NOT fast. Be patient and watch the forest grow.

W=800
H=600
canvas.width = W;
canvas.height = H;

var ctx = canvas.getContext("2d");

R=function(m) { return m * Math.random()};
RAD=function(deg) { return deg / 180 * Math.PI};
LIMIT=function(x, min, max) {return x < min ? min : x > max ? max : x};
var SPEED = 0.01, HEIGHT = 11.0;

// Ground
var grd = ctx.createLinearGradient(0,0,0,H);
grd.addColorStop(0,"#88ccff");
grd.addColorStop(0.45,"#ffffee");
grd.addColorStop(0.5,"#80cc80");
grd.addColorStop(1,"#001100");
ctx.fillStyle = grd;
ctx.fillRect(0,0, W,H);


Plot = function(dist, side, h, s, alpha, diam)
{
    var x, y, a1,a2,scale = H/4 * 3.5 / dist, 
        x0 = side * scale + s * scale + W/2,
        y0 = H/2 + 2.5*scale - h*scale;
    
    k = dist
    if (diam > 0.05) {
        red = k*3|0;     
        green = k|0;
        a1=alpha+1
        a2=alpha-1
    }
    else
    {
        green= 80+(1-diam)*k*2|0;
        red = k|0;
        a1=0;
        a2=2*Math.PI;
    }
    diam *= scale;
    h *= scale;
    s *= scale;
    ctx.beginPath();
    ctx.arc(x0,y0,diam/2, a1,a2);//lpha-1, alpha+1);//0,2*Math.PI);
    ctx.fillStyle = 'rgb('+red+','+green+',0)';
    ctx.fill();
}

Grow = function(dist, side, h, s, alpha, grown)
{
    var diam, branchLength = 0.0;
    diam = (1.0 - grown / HEIGHT) * 0.5;
    do
    {
        alpha += R(RAD(3)) - RAD(1.5);
        h += Math.sin(alpha) * SPEED;
        s += Math.cos(alpha) * SPEED;
        branchLength += SPEED;
        grown += SPEED;
        diam = (1.0 - grown / HEIGHT) * 0.5;
        Plot(dist, side, h, s, alpha, diam);
    } while(branchLength < 5 * diam + R(6 * diam) && diam > 0.02);

    if (diam > 0.02)
    {
        var br = 0;

        if(R(10) > 2) br++,Grow(dist, side, h, s, alpha + RAD(15) + R(RAD(20)), grown);
        if(R(10) > 2) br++,Grow(dist, side, h, s, alpha - RAD(15) - R(RAD(20)), grown);
        if(R(10) < 2 || br == 0) Grow(dist, side, h, s, alpha - RAD(2.5) + R(RAD(5)), grown);
    }
}

trees=[]
for(i = 0; i < 300; ++i) trees.push({ z: 1+R(70), s:R(120)-60 });
trees.sort( function (a,b) { return a.z - b.z} );

Draw = function()
{
    t = trees.pop();
    if (t)
    {
        Grow(t.z, t.s, 0, 0, RAD(90), 0);
        setTimeout(Draw, 100);
    }
    else 
    {
        var e,c,d,p,i,l, img = ctx.getImageData(0,0,W,H);
        l = img.data.length;
        for (i = 0; i < l-W*4-4; i+=4)
        {
            c = (img.data[i]+img.data[i+1])/2|0
            c = img.data[i]
            d = c > 120 + R(16) ? 255 : 0
            e = c - d;
            img.data[i]=img.data[i+1]=img.data[i+2]=d
            c = (img.data[i+4]+img.data[i+5])/2|0
            
            c = LIMIT(c + ((e*7)>>4),0,255)
            img.data[i+4]=img.data[i+5]=img.data[i+6]=c
            p = i+W*4
            c = (img.data[p-4]+img.data[p-3])/2|0
            c = LIMIT(c + ((e*3)>>4),0,255)
            img.data[p-4]=img.data[p-3]=img.data[p-2]=c
            c = (img.data[p]+img.data[p+1])/2|0
            c = LIMIT(c+ ((e*5)>>4),0,255)
            img.data[p]=img.data[p+1]=img.data[p+2]=c
            c = (img.data[p+4]+img.data[p+5]*2)/3|0
            c = LIMIT(c + (e>>4),0,255)
            img.data[p+4]=img.data[p+5]=img.data[p+6]=c
    
        }
        bwcanvas.width = W;
        bwcanvas.height = H;
        var bwx = bwcanvas.getContext("2d");
        bwx.putImageData(img,0,0);
    }
}

setTimeout(Draw, 10);

<canvas id='bwcanvas'  width="2" height="2"></canvas>
<canvas id='canvas'  width="2" height="2"></canvas>

Answer 4

Context Free Art 3 (1133)

CF is a vector graphics rendering language, so I cannot avoid anti-alising. I worked that around by drawing square at the same place several (variable N) times. Fog is done by drawing small squares on random places.

startshape main

W = 80*0.6
H = 60*0.6

N = 3

CF::Background = [ b -1 ]
CF::Size = [ x 0 y -20 s W H ]
CF::Color = 0
CF::ColorDepth = 16
CF::MinimumSize = 0.6

shape main {
  transform [ z 0 y (H/2) b 1 ]
  loop 30 [ z -1 y -2 ] {
    loop 200000 []
      SQUARE1 [ s (0.1/3) x -W..W y -H..H z -0.5..0.5 ]
  }

  transform [ b -1 z 3 ]
  loop 14 [[ s 1.1 y -0.8..-1 s 0.6 z -3 ]] {
    loop 14 [] tree [ x (-30..-20) z (-3..3) ]
    loop 14 [] tree [ x (20..30) z (-3..3) ]
  }
}

shape tree {
  branch [ ]
}

shape branch
rule 7 {
  transform [ s (1..2) 1]
  SQUARE1 [ ]

  branch [ y (0.2..0.3) x (-0.05..0.05) s 0.994 r (-6..6) z (-0.3..0.3)  ]
  branch1 [ b 0.001 z -2 r -20..20 ]
}
rule 0.001 { }
rule 0.3 { branch [ r 4..20 ] }
rule 0.3 { branch [ r -4..-20 ] }

shape branch1
rule 90 { }
rule { branch [ r -22..22 s 0.8..1 ] }

path SQUARE1 {
  MOVETO( 0.5,  0.5)
  LINETO(-0.5,  0.5)
  LINETO(-0.5, -0.5)
  LINETO( 0.5, -0.5)
  CLOSEPOLY()
  loop N [] FILL()[]
}

shape S {
  SQUARE [ a -1 ]
  loop 1000 [ ] SQUARE [ x (-0.5..0.5) y (-0.5..0.5) s 0.01..0.001 ]
}

More renders using different numbers

Answer 5

IFS with JAVA

This solution uses an Iterated Function System (IFS) to describe one (proto) tree. The IFS is applied 100 times (=forest). Before each tree is painted (planted into the forest) the IFS is altered slightly in place (random walk style). So each tree looks slightly different.

Pictures are from random seeds:

• -824737443
• -1220897877
• -644492215
• 1133984583

No dithering is needed.

import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.swing.*;

public class IFS {
    static Random random=new Random();
    static int BLACK = 0xff000000;
    static int treeCount = 100;
    static Random rand = new Random();
    static int Height = 600;
    static int Width = 800;
    static BufferedImage img = new BufferedImage(Width, Height, BufferedImage.TYPE_INT_ARGB);

    static double[][] ifs=new double[][] {//Tree 3 {; Paul Bourke  http://ecademy.agnesscott.edu/~lriddle/ifskit/gallery/bourke/bourke.ifs
       {0.050000,  0.000000,  0.000000,  0.600000,  0.000000,  0.000000,  0.028000},
       {0.050000,  0.000000,  0.000000, -0.500000,  0.000000,  1.000000,  0.023256},
       {0.459627, -0.321394,  0.385673,  0.383022,  0.000000,  0.600000,  0.279070},
       {0.469846, -0.153909,  0.171010,  0.422862,  0.000000,  1.100000,  0.209302},
       {0.433013,  0.275000, -0.250000,  0.476314,  0.000000,  1.000000,  0.555814 /*Paul Bourke has: 0.255814*/},
       {0.421325,  0.257115, -0.353533,  0.306418,  0.000000,  0.700000,  0.304651 /*Paul Bourke has: 0.204651*/},
    };

    public static void main(String[] args) {
        int seed=random.nextInt();
        //seed=-1220897877;
        random=new Random(seed);
        for (int t = 0; t < treeCount; t++) {
            for (int i = 0; i < ifs.length; i++) {
                for (int j = 0; j < ifs[0].length; j++) {
                    ifs[i][j]=R(ifs[i][j]);
                }
            }
            tree(random.nextDouble(), 0.1*random.nextDouble());
        }
        JFrame frame = new JFrame(""+seed) {
            public void paint(Graphics g) {
                setSize(800,600);
                g.drawImage(img,0,0,null);
            }
        };
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }

    private static void tree(double x0, double dist) {
        double y0=Math.atan(dist+0.01);
        double scale=Math.atan(0.01)/y0;
        double x=0;
        double y=0;
        for (int n = 0; n < 200000/Math.pow(20*dist+1, 8); n++) {
            int k = select(ifs);
            double newx=ifs[k][0]*x + ifs[k][1]*y + ifs[k][2];
            double newy=ifs[k][3]*x + ifs[k][4]*y + ifs[k][5];
            x=newx;
            y=newy;
            newx= Width*(0.5*scale*newx+x0);
            newy= Height*((1-0.5*scale*newy)-y0-0.1);
            if (0<=newx && newx<Width && 0<=newy && newy<Height) {
                img.setRGB((int)newx, (int)newy, BLACK);
            }
        }
    }

    private static double R(double x) {
        return (1+ 0.01*random.nextGaussian())*x;
    }

    private static int select(double[][] ifs) {
        int k;
        double sum=0;
        for(k=0; k<ifs.length; k++) {
            sum+=ifs[k][6];
        }
        double r=sum*random.nextDouble();
        sum=ifs[0][6];
        for(k=0; k<ifs.length-1 && r>sum; k++) {
            sum+=ifs[k+1][6];
        }
        return k;
    }
}

Answer 6

C: 301

This program creates a simple, abstract image in the PGM format. You can open it with GIMP.

int x,y,i,d,w;srand(time(NULL));unsigned char p[480000];FILE *f=fopen("a.pgm","w");fprintf(f,"P5\n800 600\n1\n");i=480000;while(i--)p[i]=i>240000|(i%800+i/800&3)!=0;i=100;while(i--){d=(11000-i*i)/99;y=300+1100/d;x=rand()%800;while(y--){w=300/d;while(w--)p[y*800+w+x]=0;}}fwrite(p, 1, 480000, f);fclose(f);

Here is an example run:

Answer 7

I noticed a distinct lack of conifers here, so I hacked something together in Python.

from PIL import Image
import random

#Generates the seed for a tree
def makeSeed(y):
    random.seed()
    seed_x = random.randint(10, 590)
    seed_y = y
    width = random.randint(5, 10)
    height = random.randint(width*5, width*30)

    return (seed_x, seed_y, width, height)

#Grows the vertical components
def growStems(seed_data, pixel_field):
    seed_x = seed_data[0]
    seed_y = seed_data[1]
    width = seed_data[2]
    height = seed_data[3]
    for x in range(seed_x, seed_x+width):
        for y in range(seed_y-height, seed_y):
            pixel_field[x][y] = (0, 0, 0)
            #Dithering
            if seed_y > 300 and seed_y < 320:
                if (x+y)%2==0:
                    pixel_field[x][y] = (255, 255, 255)
            elif seed_y >= 320 and seed_y < 340:
                if (x+y)%4==0:
                    pixel_field[x][y] = (255, 255, 255)
            elif seed_y >= 340 and seed_y < 360:
                if (x+y)%8==0:
                    pixel_field[x][y] = (255, 255, 255)

    return pixel_field

#Grows the horizontal components
def growBranches(seed_data, pixel_field):
    seed_x = seed_data[0]
    seed_y = seed_data[1]
    width = seed_data[2]
    height = seed_data[3]
    branch_height = seed_y-height
    branch_width = width
    branch_length = 2
    max_prev = branch_length
    branches = []
    while(branch_height >= seed_y-height and branch_height < seed_y-(3*width) and branch_length < height/3):
        branches.append((branch_height, branch_width, branch_length))
        branch_height+= 4
        branch_length+=2
        #Gives the conifer unevenness to make it look more organic
        if random.randint(0,110) > 100 and branch_length > max_prev:
            max_prev = branch_length
            branch_length -= branch_length/4
    max_length = height/3


    for x in range(seed_x-max_length, seed_x+max_length):
        for y in range(seed_y-height, seed_y):
            for branch in branches:
                bh = branch[0]
                bw = branch[1]
                bl = branch[2]
                #Establishing whether a point is "in" a branch
                if x >= seed_x-bl+(width/2) and x <= seed_x+bl+(width/2):
                    if x > 1 and x < 599:
                        if y >= bh-(bw/2) and y <= bh+(bw/2):
                            if y < 400 and y > 0:
                                pixel_field[x][y] = (0, 0, 0)
                                #Dithering
                                if seed_y > 300 and seed_y < 320:
                                    if (x+y)%2==0:
                                        pixel_field[x][y] = (255, 255, 255)
                                elif seed_y >= 320 and seed_y < 340:
                                    if (x+y)%4==0:
                                        pixel_field[x][y] = (255, 255, 255)
                                elif seed_y >= 340 and seed_y < 360:
                                    if (x+y)%8==0:
                                        pixel_field[x][y] = (255, 255, 255)

    return pixel_field


def growTrees(n):
    pixel_field = [[(255, 255, 255) for y in range(400)] for x in range(600)]
    #Create the ground
    for i in range(600):    
        for j in range(400):
            if pixel_field[i][j]==(255,255,255) and j > 300:
                if (i+j)%2 == 0:
                    pixel_field[i][j]=(0,0,0)
    seed_ys=[]
    #Generates seeds for the trees and orders them back to front to make the dithering work
    for t in range(n):
        seed_ys.append(random.randint(300,390))
    seed_ys.sort()

    for s in range(len(seed_ys)):
        seed= makeSeed(seed_ys[s])
        pixel_field = growStems(seed, pixel_field)
        pixel_field = growBranches(seed, pixel_field)
    return pixel_field

def makeForest():
    forest = growTrees(25)
    img = Image.new( 'RGB', (600,400), "white") # create a new black image
    pixels = img.load() # create the pixel map
    for i in range(img.size[0]):    # for every pixel:
        for j in range(img.size[1]):
            if pixels[i,j]==(255,255,255) and j > 300:
                if (i+j)%2 == 0:
                    pixels[i,j]=(0,0,0)
            pixels[i,j] = forest[i][j] # set the colour accordingly

    img.save("Forest25.jpg")

if __name__ == '__main__':
    makeForest()

This was my first Code Golf, it was a lot of fun!

Answer 8

This answer isn't as pretty as I hoped, but it's a stepping stone to a more 3D idea I'm working on, and I really like the idea of actually simulating which trees get resources

package forest;

import java.awt.BorderLayout;
import java.awt.Canvas;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Forest extends Canvas{
    private int[] heights = new int[800];
    private BufferedImage buffered_image;
    File outputFile = new File("saved.png");
    Random r = new Random();
    public Forest() {
        buffered_image = new BufferedImage(800, 600,
                BufferedImage.TYPE_INT_RGB);
        for( int j = 0; j < 800; j++){
            heights[j] = -10000;
            for(int k = 0; k < 600; k++){
                buffered_image.setRGB(j, k, 0xFFFFFF);
            }
        }
        for(int i = 0; i < 7; i ++){
            heights[r.nextInt(800)] = 0;
        }

        this.setPreferredSize(new Dimension(800, 600));
        this.setSize(new Dimension(800, 600));
        for( int i = 0; i < 200000; i++){
            int x = r.nextInt(798) + 1;
            heights[x] =  Math.min(599, heights[x - 1] == heights[x + 1] ? heights[x] : Math.max(Math.max(heights[x - 1], heights[x]),heights[x + 1]) + 1);
            buffered_image.setRGB(x, Math.min(599, 600 - heights[x]), 0);
        } 

        try {

            ImageIO.write(buffered_image, "png", outputFile);
        } catch (IOException e) {

        }
        update();
    }
    public void repaint(){
        if(this.getGraphics() != null)
        paint(this.getGraphics());
    }


    public void paint(Graphics g) {
        g.drawImage(buffered_image, 0, 0, this);
    }

    public void update() {  
        repaint();
    }

    public static void main(String[] args) throws IOException {
        JFrame main_frame = new JFrame();
        main_frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel top_panel = new JPanel();
        top_panel.setLayout(new BorderLayout());
        Forest s = new Forest();
        top_panel.add(s, BorderLayout.CENTER);
        main_frame.setContentPane(top_panel);

        main_frame.pack();
        main_frame.setVisible(true);
    }

}