Canvas Contrast custom filter?

Question

JavaScript

Hello. Tell me please. Due to the fact that Safari does not support context.filter, you need to implement a custom filter, I did it according to google , but the result between the contrast in context.filter and the google function is different

Thank you.
P.S. For some reason, the codepen is not inserted as a block, here is a link to Codepen

Answer 1

https://codepen.io/anon/pen/EMbKyr?editors=0010
stolen from here https://stackoverflow.com/questions/10521978/html5...