Use a clip path instead of a mask to avoid clearing the canvas

[flozz]

Hello,

Currently perspective.js/ts use a mask while drawing the image to the canvas. This mask causes a clearing of the canvas. As webkit now supports antialising on clip paths, I reverted perspective.js lib to use clip path and I made this PR to help you integrating this change too :)

More information in the following issue:

• Clearing active canvas problem wanadev/perspective.js#9

[sserranoa]

Hi!

Do you have any update on this issue? I have the same problem.

With the solution of @flozz, its work ok.

Maybe it's posible merge the pull request? if not i do a fork, but... i would prefer, use the same library.

Thanks you!