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C# - Bitmap to ASCII-Art

Veröffentlicht von am 02.12.2007
(4 Bewertungen)
Wandelt ein Bitmap in ASCII Art um. Der Code zeigt nur die prinzipielle Vorgehensweiße und kann noch sehr stark optimiert werden. Kleine Rastergrafiken sollten zuvor durch Skalierung vergrößert werden um gute Ergebnisse zu erhalten.
namespace Helper
{
    namespace Imaging
    {
        static class Imaging
        {
            /// <summary>
            /// Converts a colored bitmap to a grayscale bitmap.
            /// http://loop.servehttp.com/~vertexwahn/oldwiki/public_html_an_turing/FarbbildGrauwertbild.pdf
            /// </summary>
            /// <param name="sourceBitmap"></param>
            /// <returns></returns>
            public static System.Drawing.Bitmap ConvertToGrayscale(System.Drawing.Bitmap sourceBitmap)
            {
                System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(sourceBitmap.Width,
                        sourceBitmap.Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);

                for (int y = 0; y < bitmap.Height; y++)
                    for (int x = 0; x < bitmap.Width; x++)
                    {
                        System.Drawing.Color color = sourceBitmap.GetPixel(x, y);
                        int grayscale = ((77 * color.R) + (151 * color.G) + (28 * color.B)) >> 8;
                        bitmap.SetPixel(x, y, System.Drawing.Color.FromArgb(0, grayscale, grayscale, grayscale));
                    }

                return bitmap;
            }

            /// <summary>
            /// Gets the bitmap from URL.
            /// http://dotnet-snippets.de/dns/image-aus-url-laden-SID509.aspx 
            /// </summary>
            /// <param name="url">The URL.</param>
            /// <returns></returns>
            public static System.Drawing.Bitmap GetImageFromURL(string url)
            {
                System.Net.HttpWebRequest httpWebRequest = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(url);
                System.Net.HttpWebResponse httpWebReponse = (System.Net.HttpWebResponse)httpWebRequest.GetResponse();
                System.IO.Stream stream = httpWebReponse.GetResponseStream();
                return new System.Drawing.Bitmap(System.Drawing.Image.FromStream(stream));
            }

            /// <summary>
            /// Computes the avarange grayscale value of a certain bitmap region.
            /// </summary>
            /// <param name="grayscaleBitmap">A grayscale bitmap.</param>
            /// <param name="rectangle">Defines a region.</param>
            /// <returns></returns>
            public static int GetAvarageGrayscale(System.Drawing.Bitmap grayscaleBitmap,
                System.Drawing.Rectangle rectangle)
            {
                int average = 0;

                try
                {
                    for (int y = rectangle.Y; y < rectangle.Bottom; y++)
                        for (int x = rectangle.X; x < rectangle.Right; x++)
                        {
                            average += grayscaleBitmap.GetPixel(x, y).R;
                        }
                }
                catch (System.Exception ex)
                {
                    return 128;
                }

                return average / (rectangle.Width * rectangle.Height);
            }

            /// <summary>
            /// Computes the difference between to different bitmap regions.
            /// </summary>
            /// <param name="grayscaleBitmapA">First bitmap.</param>
            /// <param name="compareRectA">First bitmap region.</param>
            /// <param name="grayscaleBitmapB">Secound bitmap</param>
            /// <param name="compareRectB">Secound bitmap region.</param>
            /// <returns></returns>
            public static int ComputeDistance(System.Drawing.Bitmap grayscaleBitmapA,
                                System.Drawing.Rectangle compareRectA,
                                System.Drawing.Bitmap grayscaleBitmapB,
                                System.Drawing.Rectangle compareRectB)
            {
                int averageA = GetAvarageGrayscale(grayscaleBitmapA, compareRectA);
                int averageB = GetAvarageGrayscale(grayscaleBitmapB, compareRectB);

                return System.Math.Abs(averageA - averageB);
            }

            /// <summary>
            /// Applies an edge filter to the bitmap.
            /// </summary>
            /// <param name="bitmap">A bitmap.</param>
            /// <returns>Edge bitmap.</returns>
            public static System.Drawing.Bitmap DetectEdges(System.Drawing.Bitmap bitmap)
            {
                System.Drawing.Bitmap grayscaleMap = ConvertToGrayscale(bitmap);

                System.Drawing.Bitmap edgeMap =
                    new System.Drawing.Bitmap(grayscaleMap.Width, grayscaleMap.Height, System.Drawing.Imaging.PixelFormat.Format24bppRgb);

                for (int y = 1; y < edgeMap.Height - 1; y++)
                {
                    for (int x = 1; x < edgeMap.Width - 1; x++)
                    {
                        int sum = System.Math.Abs(grayscaleMap.GetPixel(x - 1, y - 1).R + grayscaleMap.GetPixel(x, y - 1).R + grayscaleMap.GetPixel(x + 1, y - 1).R
                            - grayscaleMap.GetPixel(x - 1, y + 1).R - grayscaleMap.GetPixel(x, y + 1).R - grayscaleMap.GetPixel(x + 1, y + 1).R);

                        System.Drawing.Color z1 = grayscaleMap.GetPixel(x - 1, y - 1);
                        System.Drawing.Color z2 = grayscaleMap.GetPixel(x, y - 1);
                        System.Drawing.Color z3 = grayscaleMap.GetPixel(x + 1, y - 1);
                        System.Drawing.Color z4 = grayscaleMap.GetPixel(x - 1, y + 1);
                        System.Drawing.Color z5 = grayscaleMap.GetPixel(x, y + 1);
                        System.Drawing.Color z6 = grayscaleMap.GetPixel(x + 1, y + 1);

                        int foo = z1.R + z2.R + z3.R - z4.R - z5.R - z6.R;
                        if (sum > 255)
                            sum = 255;

                        sum = 255 - sum;

                        edgeMap.SetPixel(x, y, System.Drawing.Color.FromArgb(255, sum, sum, sum));
                    }
                }

                return edgeMap;
            }

            /// <summary>
            /// Converts a bitmap to ascii art.
            /// </summary>
            /// <param name="bitmap">A bitmap.</param>
            /// <returns>Ascii art.</returns>
            /// <example>
            /* 0:::::::::::::::::::::::::::::$MMMMM%:::::::::::::::::::::::::::::::::::::M
                %                            (#''` !M8                                    M
                %                    :QMMMMMMMM849640MMM@(                                M
                %                 "MMMMMMM4*' HM:  !MB#MMMMMM$                            M
                %               'MMMM3        ''$844$    `6MMMMM'                         M
                % '#MNN#H@@@@@@HMMM!          '''`           $MMM3                        M
                %1M@99889QB81!!M*M4'`                          @QM:                       M
                %1Q'"B000008MMM*`MM:`''`                       !M@3                :&$;`  M
                %0`  $`      !B  `*MM6  ''''`                 'MM(!:            $MMMMMMMMMM
                %!&  `8'     #`    ''1MM@H3'`'''`         '$MMMH   %          4M$''!@BMMM4M
                % ;0   46   (3       `''''1#@HBH#&$&$448MMMM0'     :'       (M& ':@BQ@"   M
                %  !B(16BMQ`B                       :894:          `*     'MH   B8Q0`     M
                %    &MM` *M&                      !4               ;:"Q#M#'  !@3Q`       M
                %      4MM;&`                      "                (01'`'''`"Q0"         M
                %        :MN                      `(                `'''`  '84B'          M
                %                                 &                 `` `''QB09`           M
                %          !                     :(                 '389088@;             M
                %          1:                   '9                  !"6QQQ!               M
                %          `#                  :B                  `84'                   M
                %           (#                04                   &'                     M
                %            1M6           `9B!                   $:                      M
                %             !M#006(:'"6490`                   `Q:                       M
                %               4B! :(1!                      `48`                        M
                %                 4@9'                      ;@B!                          M
                %                   '9QB0!              ;8QB3                             M
                %                       `&88909444099898%                                 M
                0:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::M 
            */
            /// </example>
            public static string ConvertToAsciiArt(System.Drawing.Bitmap bitmap)
            {
                System.Drawing.Bitmap edgeMap = DetectEdges(bitmap);

                string output = "";

                for (int y = 0; y < edgeMap.Height; y += 13)
                {
                    for (int x = 0; x < edgeMap.Width; x += 8)
                    {
                        int minDistance = 999999999;
                        char minChar = ' ';

                        for (int i = 32; i < 127; i++)
                        {
                            char c = (char)i;
                            string str = "" + c;

                            System.Drawing.Bitmap characterMap =
                                new System.Drawing.Bitmap(8, 13, System.Drawing.Imaging.PixelFormat.Format24bppRgb);
                            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(characterMap);
                            g.FillRectangle(new System.Drawing.SolidBrush(System.Drawing.Color.White),
                                            new System.Drawing.Rectangle(0, 0, characterMap.Width, characterMap.Height));
                            g.DrawString(str,
                                new System.Drawing.Font("Courier New", 10),
                                new System.Drawing.SolidBrush(System.Drawing.Color.Black), -2, -2);

                            int tmp = ComputeDistance(characterMap,
                                new System.Drawing.Rectangle(0, 0, characterMap.Width, characterMap.Height),
                                edgeMap,
                                new System.Drawing.Rectangle(x, y, characterMap.Width, characterMap.Height));

                            if (tmp < minDistance)
                            {
                                minDistance = tmp;
                                minChar = c;
                            }
                        }

                        output += minChar;
                    }

                    output += "\r\n";
                }

                return output;
            }
        }
    }

    namespace UnitTests
    {
        [TestFixture]
        public class TestImaging
        {
            [Test]
            public void TestConvertToAsciiArt()
            {
                System.Drawing.Bitmap bmp = Helper.Imaging.Imaging.GetImageFromURL(@"http://www.uni-koblenz.de/~stefmu/npr/teapot1.jpg");
                string assciiArt = Helper.Imaging.Imaging.ConvertToAsciiArt(bmp);
            }
        }
    }
}
Abgelegt unter ASCII-Art, ASCII, Grafik, ASCII-Kunst.

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