New Post: ToBase64 is always different for same image

I am converting a PDF to image and sending back to client Base 64 encoding string

using (MagickImage pdfConvertedImage = images[index])

                    {
                        // ReSharper restore AccessToDisposedClosure
                        //// set the format of the image
                        pdfConvertedImage.Format = MagickFormat.Png;
                        pdfConvertedImage.Resize(new MagickGeometry(width, height));                    

                        var keyValuePair = new KeyValuePair<string, string>(
                                    string.Format(imageFolderPath + FilePng, index),
                                    pdfConvertedImage.ToBase64());

                        imageCollection.Add(keyValuePair);

}

But, the Base64 string is always different for the Image. For the same resolution, I should expect the image to be exact, ie the base 64 encoded string , should match, but its not happening.

Can you please help me.

I am using
<package id="Magick.NET-Q8-x64" version="7.0.0.0009" targetFramework="net451" />