Problem
1. Write a function to draw a simple face with eyes and a mouth. on a picture.
2. Now use your simple face function in a loop to draw a whole crowd of people.
3. Create a watermark function to blend a watermark onto an image, in which the position of the watermark can be a tile, scale, or a tuple (X, Y). Also consider the opacity value between 0 and 1 to make the image less intrusive.