WkhtmlDriver.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;

namespace Wkhtmltopdf.NetCore
{
    public abstract class WkhtmlDriver
    {
        /// <summary>
        /// Converts given URL or HTML string to PDF.
        /// </summary>
        /// <param name="wkhtmlPath">Path to wkthmltopdf\wkthmltoimage.</param>
        /// <param name="switches">Switches that will be passed to wkhtmltopdf binary.</param>
        /// <param name="html">String containing HTML code that should be converted to PDF.</param>
        /// <returns>PDF as byte array.</returns>
        public static byte[] Convert(string wkhtmlPath, string switches, string html)
        {
            // switches:
            //     "-q"  - silent output, only errors - no progress messages
            //     " -"  - switch output to stdout
            //     "- -" - switch input to stdin and output to stdout
            switches = "-q " + switches + " -";

            // generate PDF from given HTML string, not from URL
            if (!string.IsNullOrEmpty(html))
            {
                switches += " -";
                html = SpecialCharsEncode(html);
            }

            string rotativaLocation;

            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            {
                rotativaLocation = Path.Combine(wkhtmlPath, "Windows", "wkhtmltopdf.exe");
            }
            else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
            {
                rotativaLocation = Path.Combine(wkhtmlPath, "Mac", "wkhtmltopdf");
            }
            else
            {
                rotativaLocation = Path.Combine(wkhtmlPath, "Linux", "wkhtmltopdf");
            }

            if (!File.Exists(rotativaLocation))
            {
                throw new Exception("wkhtmltopdf not found, searched for " + rotativaLocation);
            }

            using (var proc = new Process())
            {
                try
                {
                    proc.StartInfo = new ProcessStartInfo
                    {
                        FileName = rotativaLocation,
                        Arguments = switches,
                        UseShellExecute = false,
                        RedirectStandardOutput = true,
                        RedirectStandardError = true,
                        RedirectStandardInput = true,
                        CreateNoWindow = true
                    };

                    proc.Start();
                }
                catch (Exception ex)
                {
                    throw ex;
                }

                // generate PDF from given HTML string, not from URL
                if (!string.IsNullOrEmpty(html))
                {
                    using (var sIn = proc.StandardInput)
                    {
                        sIn.WriteLine(html);
                    }
                }

                using (var ms = new MemoryStream())
                {
                    using (var sOut = proc.StandardOutput.BaseStream)
                    {
                        byte[] buffer = new byte[4096];
                        int read;

                        while ((read = sOut.Read(buffer, 0, buffer.Length)) > 0)
                        {
                            ms.Write(buffer, 0, read);
                        }
                    }

                    string error = proc.StandardError.ReadToEnd();

                    if (ms.Length == 0)
                    {
                        throw new Exception(error);
                    }

                    proc.WaitForExit();

                    return ms.ToArray();
                }
            }
        }

        /// <summary>
        /// Encode all special chars
        /// </summary>
        /// <param name="text">Html text</param>
        /// <returns>Html with special chars encoded</returns>
        private static string SpecialCharsEncode(string text)
        {
            var chars = text.ToCharArray();
            var result = new StringBuilder(text.Length + (int)(text.Length * 0.1));

            foreach (var c in chars)
            {
                var value = System.Convert.ToInt32(c);
                if (value > 127)
                    result.AppendFormat("&#{0};", value);
                else
                    result.Append(c);
            }

            return result.ToString();
        }
    }
}