Convert PNG to GIF or JPG

Question

I am trying to convert png image to gif and jpg format. I am using the code that I've found at Microsoft documentation.

I've created git-hub example by modifying this code into this:

        public static void Main(string[] args)
        {
            // Load the image.
            using (Image png = Image.FromFile("test-image.png"))
            {
                var withBackground = SetWhiteBackground(png);
                // Save the image in JPEG format.
                withBackground.Save("test-image.jpg");

                // Save the image in GIF format.
                withBackground.Save("test-image.gif");
                withBackground.Dispose();
            }
        }

        private static Image SetWhiteBackground(Image img)
        {
            Bitmap imgWithBackground = new Bitmap(img.Width, img.Height);
            Rectangle rect = new Rectangle(Point.Empty, img.Size);
            using (Graphics g = Graphics.FromImage(imgWithBackground))
            {
                g.Clear(Color.White);
                g.DrawImageUnscaledAndClipped(img, rect);
            }

            return imgWithBackground;
        }

Original image (fictional data) is this:

And when I convert it to gif I get this:

So my question: is there a way to get gif format out of png that would look the same?

Edit: Hans Passant pointed out that the root problem was transparent background. After some digging I found answer here. I used code snipped mentioned in the link to set background to white:

        private Image SetWhiteBackground(Image img)
        {
            Bitmap imgWithBackground = new Bitmap(img.Width, img.Height);
            Rectangle rect = new Rectangle(Point.Empty, img.Size);
            using (Graphics g = Graphics.FromImage(imgWithBackground))
            {
                g.Clear(Color.White);
                g.DrawImageUnscaledAndClipped(img, rect);
            }

            return imgWithBackground;
        }

So now the gif looks like this:

Answer 1

Something like (https://docs.sixlabors.com/articles/imagesharp/gettingstarted.html):

using SixLabors.ImageSharp;
using SixLabors.ImageSharp.Processing;

// Open the file and detect the file type and decode it.
// Our image is now in an uncompressed, file format agnostic, structure in-memory as a series of pixels.
using (Image image = Image.Load("test-image.png")) 
{     
    // The library automatically picks an encoder based on the file extensions then encodes and write the data to disk.
    image.Save("test.gif"); 
}