Prime Visualiser

gistfile1.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Net.Mime;

namespace ConsoleTestApp
{
	public class PrimeVisualiser
	{
		private const int BORDER_WIDTH = 5;
		private const int SQUARE_SIZE = 64;
		private const int CLOSE_BOUND = 60;
		private const int SUBDIV_GAP = 2;

		private readonly SolidBrush m_white = new SolidBrush( Color.White );
		private readonly SolidBrush m_textBackground = new SolidBrush( Color.FromArgb( 128, Color.Black ) );
		private readonly Dictionary<int, SolidBrush> m_usedColors = new Dictionary<int, SolidBrush>();
		private Font m_font;
		private int m_seed;

		public Bitmap Run( int max, int columns = 10 )
		{
			m_usedColors.Clear();
			m_usedColors[0] = new SolidBrush( Color.Black );
			m_usedColors[1] = new SolidBrush( Color.White );
			m_font = new Font( FontFamily.GenericSansSerif, 20 );
			m_seed = DateTime.Now.Millisecond;

			int width = ( columns * SQUARE_SIZE ) + ( BORDER_WIDTH * ( columns + 1 ) );
			int rows = max / columns;
			int height = ( rows * SQUARE_SIZE ) + ( BORDER_WIDTH * ( rows + 1 ) );

			Bitmap b = new Bitmap( width, height );

			using( Graphics g = Graphics.FromImage( b ) )
			{
				g.FillRectangle( m_white, 0, 0, width, height );

				for( int y = 0; y < max; y++ )
				{
					for( int x = 0; x < 10 && ( y * columns ) + x < max; x++ )
					{
						int val = ( ( y * columns ) + x ) + 1;
						DrawSquare( g, val, x, y );
					}
				}
			}

			return b;
		}

		private void DrawSquare( Graphics g, int value, int col, int row )
		{
			int x = ( col * SQUARE_SIZE ) + ( BORDER_WIDTH * col );
			int y = ( row * SQUARE_SIZE ) + ( BORDER_WIDTH * row );

			List<int> factors = GetPrimeFactors( value ).ToList();

			SolidBrush brush;
			if( factors.Count == 1 ) // prime number
			{
				brush = GetNextColor( value );
				m_usedColors.Add( value, brush );
				g.FillRectangle( brush, x + BORDER_WIDTH, y + BORDER_WIDTH, SQUARE_SIZE, SQUARE_SIZE );
			} else if( factors.Count == 0 )
			{
				// Is 1
				brush = m_usedColors[1];
				g.FillRectangle( brush, x + BORDER_WIDTH, y + BORDER_WIDTH, SQUARE_SIZE, SQUARE_SIZE );
			} else
			{
				// Subdivide, and get colours by factors.
				int gapCount = factors.Count - 1;
				int subdivWidth = ( SQUARE_SIZE - ( gapCount * SUBDIV_GAP ) ) / factors.Count;

				for( int i = 0; i < factors.Count; i++ )
				{
					int subdivX = ( i * subdivWidth ) + ( i * SUBDIV_GAP );
					g.FillRectangle( m_usedColors[factors[i]], x + subdivX + BORDER_WIDTH, y + BORDER_WIDTH, subdivWidth, SQUARE_SIZE );
				}
			}

			int textY = SQUARE_SIZE - 25;

			g.FillRectangle( m_textBackground, x + BORDER_WIDTH, y + textY - 1 + BORDER_WIDTH, SQUARE_SIZE, SQUARE_SIZE - textY + 1 );
			g.DrawString( value.ToString(), m_font, m_white, x + 3, y + textY );
		}

		private SolidBrush GetNextColor( int val )
		{
			Random rand = new Random( val + m_seed );
			int r, g, b;

			do
			{
				r = rand.Next( 255 );
				g = rand.Next( 255 );
				b = rand.Next( 255 );
			} while( ColourTooClose( r, g, b ) );

			return new SolidBrush( Color.FromArgb( r, g, b ) );
		}

		private bool ColourTooClose( int r, int g, int b )
		{
			foreach( var brush in m_usedColors )
			{
				Color col = brush.Value.Color;

				if( Math.Abs( r - col.R ) < CLOSE_BOUND &&
					Math.Abs( g - col.G ) < CLOSE_BOUND &&
					Math.Abs( b - col.B ) < CLOSE_BOUND )
				{
					return true;
				}
			}

			return false;
		}

		private IEnumerable<int> GetPrimeFactors( int n )
		{
			// 2 first, save time later.
			while( n > 1 )
			{
				if( n % 2 != 0 )
					break;

				yield return 2;
				n >>= 1;
			}

			int div = 3;
			while( n > 1 )
			{
				if( n % div != 0 )
				{
					div += 2;
					continue;
				}

				yield return div;
				n /= div;
			}
		}
	}
}