Draws using Canvas dissapears when image is zoomed

[femosso]

I'm drawing lines over the ImageViewTouch image using canvas. For this I overrided the method onDrawn in ImageViewTouch class and there I make some lines drawing.

The lines are drawn normally in the image, however when I zoom it the lines simply dissapears.

How can I 'save' the draw in the image so that the lines are zoom along the image?