Pyramid.cs

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Imaging;
using System.Linq;

namespace ConsoleTestApp
{
	public class Pyramid
	{
		private const int PRIME_COLOUR_R = 0x00, PRIME_COLOUR_G = 0x00, PRIME_COLOUR_B = 0x00;
		private const int N_PRIME_COLOUR_R = 0xC3, N_PRIME_COLOUR_G = 0xC3, N_PRIME_COLOUR_B = 0xC3;
		
		private const int SPACING = 1;
		private const int SQUARE_SIZE = 2;
		private const int MARGIN = 5;

		public static void Generate( int height, string filename )
		{
			int rowSize = 1;
			int itemCount = 0;
			List<List<bool>> data = new List<List<bool>>();
			List<bool> curRow = new List<bool>();

			for( int i = 0; i < height * height; i++ )
			{
				itemCount++;
				curRow.Add( IsPrime( i ) );

				if( rowSize == itemCount )
				{
					data.Add( curRow );
					curRow = new List<bool>();
					rowSize += 2;
					itemCount = 0;
				}
			}

			SaveImage( data, filename );
		}

		private static bool IsPrime( int n )
		{
			if( n < 2 )
				return false;
			if ( n == 2 || n == 3 || n == 5 )
				return true;
			if( n % 2 == 0 || n % 3 == 0 || n % 5 == 0 )
				return false;

			int m = (int)Math.Sqrt( n );
			for( int i = 7; i < m; i += 2 )
			{
				if( n % i == 0 )
					return false;
			}

			return true;
		}

		private static void SaveImage( List<List<bool>> data, string filename )
		{
			if( data.Count == 0 )
				throw new Exception( "Data is empty." );

			int height = ( data.Count * SQUARE_SIZE ) + ( data.Count - 1 ) * SPACING;
			int width = ( data.Last().Count * SQUARE_SIZE ) + ( data.Last().Count - 1 ) * SPACING;
			if( data.Last().Count % 2 == 0 )
				width += ( SQUARE_SIZE + SPACING );

			height += MARGIN * 2;
			width += MARGIN * 2;

			Bitmap bmp = new Bitmap( width, height, PixelFormat.Format24bppRgb );
			Graphics g = Graphics.FromImage( bmp );
			List<bool> curRow;
			SolidBrush primeBrush = new SolidBrush( Color.FromArgb( PRIME_COLOUR_R, PRIME_COLOUR_G, PRIME_COLOUR_B ) );
			SolidBrush nPrimeBrush = new SolidBrush( Color.FromArgb( N_PRIME_COLOUR_R, N_PRIME_COLOUR_G, N_PRIME_COLOUR_B ) );

			int dataWidth = data.Last().Count;

			g.Clear( Color.White );
			for( int y = 0; y < data.Count; y++ )
			{
				curRow = data[y];
				int startX = ( dataWidth / 2 ) - ( curRow.Count / 2 );

				for( int x = startX, i = 0; i < curRow.Count; x++, i++ )
				{
					g.FillRectangle( curRow[i] ? primeBrush : nPrimeBrush, GetRectangle( x, y ) );
				}
			}

			g.Dispose();
			bmp.Save( filename );
			bmp.Dispose();
		}

		private static Rectangle GetRectangle( int x, int y )
		{
			int newY = ( y * SQUARE_SIZE ) + ( y - 1 ) * SPACING + MARGIN;
			int newX = ( x * SQUARE_SIZE ) + ( x - 1 ) * SPACING + MARGIN;

			return new Rectangle( newX, newY, SQUARE_SIZE, SQUARE_SIZE );
		}
	}
}