C#

// input:  Bitmap bm1, size w1*h1
// output: Bitmap bm2, size w2*h2
public static Bitmap ResizeImageKeepingAspectRatio(Image bm1, int w2, int h2, Brush backColor, bool centered) {
    int w1=bm1.Width;
    int h1=bm1.Height;
    Bitmap bm2=new Bitmap(w2, h2);
    Graphics g=Graphics.FromImage(bm2);
    g.FillRectangle(backColor, 0, 0, w2, h2);
    int x2=0;
    int y2=0;
    float scale=1;
    if (w1*h2>w2*h1) {// w2 is the limiting factor
       if (centered) y2=h2*w1/w2-h1;
       scale=w2/(float)w1;
    } else {          // h2 is the limiting factor
       if (centered) x2=w2*h1/h2-w1;
       scale=h2/(float)h1;
    }
    g.ScaleTransform(scale, scale);
    g.TranslateTransform(x2/2, y2/2);
    g.DrawImage(bm1, 0, 0);
    g.Dispose();
    return bm2;
}

TextBox t = new TextBox();
form1.Controls.Add(t);
t.Top = 10;
t.Left = 10;