#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:

Gives us the following:

Enjoy!