Yes, this should be possible. Use the `OxyPlot.WindowsForms.PngExporter` to write to the response stream.

Here is an example using WebAPI:

namespace WebApplication4.Controllers
{
    using System;
    using System.IO;
    using System.Net;
    using System.Net.Http;
    using System.Net.Http.Headers;
    using System.Web.Http;
    using OxyPlot;
    using OxyPlot.Series;
    using OxyPlot.WindowsForms;
    public class PlotsController : ApiController
    {
        public HttpResponseMessage Get(int id)
        {
            var model = new PlotModel { Title = "Plot #" + id };
            model.Series.Add(new FunctionSeries(Math.Sqrt, 0, 100, 0.01, "sqrt(x)"));
            var memoryStream = new MemoryStream();
            var exporter = new PngExporter();
            exporter.Export(model, memoryStream);
            var result = new HttpResponseMessage
                             {
                                 StatusCode = HttpStatusCode.OK,
                                 Content = new ByteArrayContent(memoryStream.ToArray())
                             };
            result.Content.Headers.ContentType = new MediaTypeHeaderValue("image/png");
            result.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("inline")
            {
                FileName = string.Format("plot{0}.png", id)
            };
            return result;
        }
    }
}

The result is:

You can use the `Transform` method of the axis to get the length on the screen, but it will be a bit difficult to calculate the scale of the other axis. I think you need to consider the width of the control, the margins, and set the `Minimum` and `Maximum` of the second axis.

I think this should be covered by the following feature request: https://github.com/oxyplot/oxyplot/issues/13