I've been learning how to manipulate canvas images, using some of the information available here: https://developer.mozilla.org/en-US/docs/Web/API/Canvas_API/Tutorial/Pixel_manipulation_with_canvas#Painting_pixel_data_into_a_context
In this section, the example on the website works fine - i.e. clicking the greyscale or invert buttons changes the image shown accordingly.
However, when I try to look at the code on the Codepen or Jsfiddle links provided, the examples do not seem to work. Can anyone help explain why this is?
Thanks
