#743 – ASCII Art Generator

Here’s a little ASCII Art generator that I wrote in C#.  Merry Christmas!

Main program, which accepts full path to image file to be converted:

    class Program
    {
        /// <summary>
        /// Usage:
        ///   Arg 1 - Full path to bitmap file (e.g. JPG, PNG)
        ///   Arg 2 - Width of target image, in # characters (e.g. 120)
        ///   Output: File with same name as input file but .txt extension
        /// </summary>
        /// <param name="args"></param>
        static void Main(string[] args)
        {
            try
            {
                if (args.Length < 2)
                {
                    Console.WriteLine("Usage:");
                    Console.WriteLine("  AscArt filename output-width [diagLog]");
                }
                else
                {
                    string inputFile = args[0];
                    int outputWidth = int.Parse(args[1]);

                    FileInfo fi = new FileInfo(inputFile);
                    if (!fi.Exists)
                        throw new Exception(string.Format("File {0} not found", inputFile));
                    string outputFile = Path.Combine(fi.DirectoryName, Path.GetFileNameWithoutExtension(inputFile) + ".txt");

                    Bitmap bmInput = new Bitmap(inputFile);

                    if (outputWidth > bmInput.Width)
                        throw new Exception("Output width must be <= pixel width of image");

                    // Generate the ASCII art
                    AscArt.GenerateAsciiArt(bmInput, outputFile, outputWidth);
                }
            }
            catch (Exception xx)
            {
                Console.WriteLine(string.Format("Fatal exception: {0}", xx));
            }
        }
    }

Here’s the source code for the AscArt class:

    public static class AscArt
    {
        // Typical width/height for ASCII characters
        private const double FontAspectRatio = 0.6;

        // Available character set, ordered by decreasing intensity (brightness)
        private const string OutputCharSet = "@%#*+=-:. ";

        // Alternate char set uses more chars, but looks less realistic
        private const string OutputCharSetAlternate = "$@B%8&WM#*oahkbdpqwmZO0QLCJUYXzcvunxrjft/\\|()1{}[]?-_+~<>i!lI;:,\"^`'. ";

        public static void GenerateAsciiArt(Bitmap bmInput, string outputFile, int outputWidth)
        {
            // pixelChunkWidth/pixelChunkHeight - size of a chunk of pixels that will
            // map to 1 character.  These are doubles to avoid progressive rounding
            // error.
            double pixelChunkWidth = (double)bmInput.Width / (double)outputWidth;
            double pixelChunkHeight = pixelChunkWidth / FontAspectRatio;

            // Calculate output height to capture entire image
            int outputHeight = (int)Math.Round((double)bmInput.Height / pixelChunkHeight);

            // Generate output image, row by row
            double pixelOffSetTop = 0.0;
            StringBuilder sbOutput = new StringBuilder();

            for (int row = 1; row <= outputHeight; row++)
            {
                double pixelOffSetLeft = 0.0;

                for (int col = 1; col <= outputWidth; col++)
                {
                    // Calculate brightness for this set of pixels by averaging
                    // brightness across all pixels in this pixel chunk
                    double brightSum = 0.0;
                    int pixelCount = 0;
                    for (int pixelLeftInd = 0; pixelLeftInd < (int)pixelChunkWidth; pixelLeftInd++)
                        for (int pixelTopInd = 0; pixelTopInd < (int)pixelChunkHeight; pixelTopInd++)
                        {
                            // Each call to GetBrightness returns value between 0.0 and 1.0
                            int x = (int)pixelOffSetLeft + pixelLeftInd;
                            int y = (int)pixelOffSetTop + pixelTopInd;
                            if ((x < bmInput.Width) && (y < bmInput.Height))
                            {
                                brightSum += bmInput.GetPixel(x, y).GetBrightness();
                                pixelCount++;
                            }
                        }

                    // Average brightness for this entire pixel chunk, between 0.0 and 1.0
                    double pixelChunkBrightness = brightSum / pixelCount;

                    // Target character is just relative position in ordered set of output characters
                    int outputIndex = (int)Math.Floor(pixelChunkBrightness * OutputCharSet.Length);
                    if (outputIndex == OutputCharSet.Length)
                        outputIndex--;

                    char targetChar = OutputCharSet[outputIndex];

                    sbOutput.Append(targetChar);

                    pixelOffSetLeft += pixelChunkWidth;
                }
                sbOutput.AppendLine();
                pixelOffSetTop += pixelChunkHeight;
            }

            // Dump output string to file
            File.WriteAllText(outputFile, sbOutput.ToString());
        }
    }

So converting this image:
SeanHeadShot
Gives us the following:

743-001

Enjoy!

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About Sean
Software developer in the Twin Cities area, passionate about .NET technologies. Equally passionate about my own personal projects related to family history and preservation of family stories and photos.

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