That code from your post is fairly standard image load handling, but the notable part is this line:

self.apng_supported = ctx.getImageData(0, 0, 1, 1).data[3] === 0;

Unless I'm misunderstanding, it's basically a "neat trick", like using ~~ for rounding or a fast inverse square root.

Is the intent that everyone who makes use of that trick is supposed to link back to your blog?

The notable part is the PNG file was copied exactly. He could have generated one himself.