Create PNG Image from BMP in C#. More details and explanation can be found here https://kb.aspose.com/imaging/net/how-to-create-png-image-from-bmp-in-c-sharp/

Create PNG Image from BMP in C#.cs

using System;
//Use following namespaces to create PNG image
using Aspose.Imaging;
using Aspose.Imaging.ImageOptions;

namespace CreatePNGImage
{
    class Program
    {
        static void Main(string[] args)
        {
            //Set license before creating PNG image from BMP
            Aspose.Imaging.License AsposeImagingLicense = new Aspose.Imaging.License();
            AsposeImagingLicense.SetLicense(@"c:\asposelicense\license.lic");

            //load input BMP image 
            Image BmpToPngImage = Image.Load("InputBMPImage.bmp");
            
            //set attributes of the output PNG file
            PngOptions PNGImageOptions = new PngOptions();
            PNGImageOptions.ResolutionSettings = new ResolutionSetting(300, 300);
            PNGImageOptions.CompressionLevel = 6;

            //save converted output PNG image
            BmpToPngImage.Save("OutputPNGImage.png", PNGImageOptions);

        }
    }
}