.NET (Core and Framework)

dstImg = new Bitmap(srcImage);

protected override void OnPaint(PaintEventArgs e)
{
    base.OnPaint(e);
    e.Graphics.DrawImage(dstImg, 0, 0);
    // An alternative that doesn't work any better
    //Rectangle r = new Rectangle(0, 0, srcImage.Width, srcImage.Height);
    //e.Graphics.DrawImage(dstImg, r, r, GraphicsUnit.Pixel);
    // Junxtapose original to the right of dstImg, it will have the correct size:
    e.Graphics.DrawImage(srcImage, dstImage.Width + 1, 0);
}

dstImg = new Bitmap(srcImage.Width, srcImage.Height, PixelFormat.Format24bppRgb);
Graphics g = Graphics.FromImage(dstImg);
Rectangle r = new Rectangle(0, 0, srcImage.Width, srcImage.Height);
g.DrawImage(srcImage, r, r, GraphicsUnit.Pixel);
g.Dispose();