contour.js not correct

[gcmartijn]

I get a incorrect outline that is 1px to wide at the right side.

The image i'm testing is this:
http://i.imgur.com/gIXu6GS.png

The image contour must be 140px not 141px

Using this:
http://jsfiddle.net/5v5hmo62/11/

[Breslov]

I too encounter contour.js algorithm inaccuracies.

The values of algorithm's x and y arguments could reach a negative value (of exactly -1), or exceed canvas' width or height (by exactly 1).

Allowed x value-range: [0, Width - 1]
Allowed y value-range: [0, Height - 1]