Passing an image to Kernel via NETLink

Question

I have created a specialized image analysis method in Mathematica that takes an image and returns a marked up image with some detection output. In order to allow others to feed images into my analysis from arbitrary sources (databases, file systems, web interfaces, scanners, etc), I would like to wrap in a .NET application (preferably C#).

Is there any way to pass an image object from .NET into MathKernel via NETLink and handle it as an Image in the kernel? I have found examples of how to get images out of MathKernel, but not the other direction.

I could write the image to a temporary file, but that seems sloppy.

Answer 1

I have found through a lot of iterations that the easiest and most reliable way of doing this is to pass the images using Base64 strings.

I have included example functions for sending and retrieving images using Mathematica .NETLink. The .NETLink built in function for retrieving images (EvaluateToImage) seems to re-encode the image.

Once the image is back in a byte array, saving or displaying the image should be trivial.

using System;
using System.IO;
using Wolfram.NETLink;

namespace Example
{
    class Example
    {
        private static IKernelLink ml;

        internal void InitializeKernelLink()
        {
            ml = MathLinkFactory.CreateKernelLink();
            ml.WaitAndDiscardAnswer();
        }

        internal void SendImage()
        {        
            var path = @"C:\Example.JPG";
            var imageArray = File.ReadAllBytes(path);
            var base64Image = Convert.ToBase64String(imageArray);
            ml.Evaluate("importedImage = ImportString[\"" + base64Image + "\",\"Base64\"]");
            ml.WaitAndDiscardAnswer();
        }

        internal void GetImage()
        {
            ml.Evaluate($"ExportString[importedImage,{{\"Base64\", \"PNG\"}}]");
            ml.WaitForAnswer();
            var data = ml.GetString();
            byte[] decoded = Convert.FromBase64String(data);
        }

    }
}