Read only texture

Hello,

I am trying to make a pocket tanks like game where the environment is a texture and pixels are changed to transparent and the collider is updated to destroy something. However i have run into a problem. Running the script tells me i need to make the texture readable in the import settings. I do. But then when changes are made to the texture they dont go away even after i stop and start the game again... the very asset image file is changed. How would i make a copy of the original image that i can destroy?

Thanks!