I get unexpected results from Graphics.DrawImage

To reproduce this problem, create a 2x2 black and white image in Microsoft Paint saved as D:\small.png. Then create a new WinForms application in Visual Studio with a borderless PictureBox. Then use the following code:

void f6(Graphics g)
{
    var img = Image.FromFile(@"d:\small3.png");
    var srcRect = new Rectangle(0, 0, img.Width, img.Height);
    int factor = 400;
    var destRect = new Rectangle(0, 0, img.Width * factor, img.Height * factor);
    g.DrawRectangle(new Pen(Color.Blue), destRect);
    g.DrawImage(img, destRect, srcRect, GraphicsUnit.Pixel);
}

void pictureBox1_Paint(object sender, PaintEventArgs e)
{
    f6(e.Graphics);
}

I expect the entire rectangle inside the blue margins to turn black and the output will be as follows:

Why is this happening?

OK thanks. I do not know about interpolation. now change the code as follows:

void f6(Graphics g)
{
    var img = Image.FromFile(@"d:\small3.png");
    var srcRect = new Rectangle(0, 0, img.Width, img.Height);
    int factor = 200;
    var destRect = new Rectangle(0, 0, img.Width * factor, img.Height * factor);
    g.FillRectangle(new SolidBrush(Color.DarkCyan), pictureBox1.ClientRectangle);
    g.InterpolationMode = InterpolationMode.NearestNeighbor;
    g.DrawRectangle(new Pen(Color.Blue), destRect);
    g.DrawImage(img, destRect, srcRect, GraphicsUnit.Pixel);
}

it produces the following result:

Result3

- . 6060 . , 2x2. . , GDI + destRect srcRect?! , , . , , . ++ StretchBlt . .