在图像上保存文本块

我找到了很多Windows Phone 8/8.1的例子，但我似乎找不到Window 10 UWP的例子。

所以我需要的是图像上的可移动文本块。我似乎不知道如何加载图像，写一些文本然后保存。

我目前拥有的代码[不起作用]

//first, create a dummy bitmap just to get a graphics object
            Image img = new Bitmap(1, 1);
            Graphics drawing = Graphics.FromImage(img);
            //measure the string to see how big the image needs to be
            SizeF textSize = drawing.MeasureString(text, font);
            //free up the dummy image and old graphics object
            img.Dispose();
            drawing.Dispose();
            //create a new image of the right size
            img = new Bitmap((int)textSize.Width, (int)textSize.Height);
            drawing = Graphics.FromImage(img);
            //paint the background
            drawing.Clear(backColor);
            //create a brush for the text
            Brush textBrush = new SolidBrush(textColor);
            drawing.DrawString(text, font, textBrush, 0, 0);
            drawing.Save();
            textBrush.Dispose();
            drawing.Dispose();