ex winform：
Graphics g = Graphics.FromImage(newimg);
String str = "hello world";
Font font = new Font("Arial", 30);
SolidBrush sbrush = new SolidBrush(Color.Black);
g.DrawString(str, font, sbrush, new PointF(100, 120));
In the WPF on how the InteropBitmap to do the same thing?
The graphics object in Wpf is different than Winforms since Wpf uses Vector Graphics. In Wpf you will be using a DrawingVisual, DrawingContext, FormattedText and a BitmapImage, the DrawingContext is equivalent to the Graphics object in Winforms. This is a quick example to show what I mean.