Javascript – Optimizing image load times. (thinking differently)

It might be 7 years too late, but I came across this question while trying to solve this problem. I eventually managed to do it and this is the solution. For PNG you first need to install nQuant using NuGet.

include:

using System.Web.Hosting;
using System.IO;
using System.Diagnostics;
using nQuant;
using System.Drawing;
using System.Drawing.Imaging;

Methods:

    public void optimizeImages()
    {
        string folder = 
            Path.Combine(HostingEnvironment.ApplicationPhysicalPath, @"assets\temp");
        var files = Directory.EnumerateFiles(folder);

        foreach (var file in files)
        {
            switch (Path.GetExtension(file).ToLower())
            {
                case ".jpg":
                case ".jpeg":
                    optimizeJPEG(file);
                    break;
                case ".png":
                    optimizePNG(file);
                    break;
            }

        }

    }

    private void optimizeJPEG(string file)
    {
        string pathToExe = HostingEnvironment.MapPath("~\\adminassets\\exe\\") + "jpegtran.exe";

        var proc = new Process
        {
            StartInfo =
            {
                Arguments = "-optimize \"" + file + "\" \"" + file + "\"",
                FileName = pathToExe,
                UseShellExecute = false,
                CreateNoWindow = false,
                WindowStyle = ProcessWindowStyle.Hidden,
                RedirectStandardError = true,
                RedirectStandardOutput = true
            }
        };

        Process jpegTranProcess = proc;

        jpegTranProcess.Start();
        jpegTranProcess.WaitForExit();
    }

    private void optimizePNG(string file)
    {
        string tempFile = Path.GetDirectoryName(file) + @"\temp-" + Path.GetFileName(file);
        int alphaTransparency = 10;
        int alphaFader = 70;
        var quantizer = new WuQuantizer();
        using (var bitmap = new Bitmap(file))
        {
            using (var quantized = quantizer.QuantizeImage(bitmap, alphaTransparency, alphaFader))
            {
                quantized.Save(tempFile, ImageFormat.Png);

            }

        }
        System.IO.File.Delete(file);
        System.IO.File.Move(tempFile, file);
    }

It will take all files from /assets/temp folder and optimize jpegs and PNG. I followed this question for the png part. The jpeg part I scraped from several sources. Including PicJam and Image Optimizer. The way I use it is by uploading all files from the user to the temp folder, running this method, uploading the files to azure blob storage, and deleting the local files. I downloaded jpegtran here.