I want to draw a line over a picture image

I am trying to draw lines, points over an image. right now they are underneath the picture. Can someone show me how?

also the lines are speed like…I would like to know if I can make the line larger on one end…and skinny on the opposite.

Try to clear depth buffer just after drawing the image.

line larger on one end…and skinny on the opposite

This is called a triangle.