New Post: Merge two images into one

I want to merge two images into one. I read that I should use WriteableBitmapEx library and use blit method. Both of my images are Image type.

So, should I first convert Image type to WriteableBitmap ?
Like this:

    var im1 = image1.ToImage().ToBitmap(); 
    var im2 = image2.ToImage().ToBitmap();

And how can I use method blit now ?