Add browser compatible API

[LinusU]

This PR modifies the API to a few wrapper functions that are provided both for Node.js and the browser. Using a tool like browserify it should be easy to write code that works both on the backend and the frontend 🙌

ref: #833

[zbjornson]

meant to be a devDependency?

[LinusU]

Great catch!

[zbjornson]

Do cases 0 and 1 exist? MDN only documents new ImageData(arr, w, h) and ImageData(w, h).

Also, would this be the same as return new ImageData(...arguments)? EDIT: (Or what you have in index.js, where you're just passing three args, and height may be undefined.)

[LinusU]

0 and 1 doesn't exist, I added them to get the errors reported back to be accurate.

return new ImageData(...arguments) would be perfect, but unfortunately Node.js 4.x doesn't support it... It's doing this since passing (10, 10, undefined) doesn't do what you want it to in the browsers:

Not 100% sure that this is the best approach though 🤔

[zbjornson]

Ah, clever :) and now I understand what your comment means.

[zbjornson]

@LinusU I started playing more with this and realized one thing to consider changing. This PR hid the ImageData constructor, so you can't do xx instanceof ImageData or new ImageData(...) anymore, for example. Browsers provide ImageData, so I think it should still be exposed.

[zbjornson]

Actually, a lot of stuff got hidden...

> /* 2.0 */ Canvas.
[inherited from Object, snip]

Canvas.createCanvas          Canvas.createImageData       Canvas.loadImage             Canvas.parseFont

> /* 1.6 */ Canvas.
[inherited from Object, snip]

[inherited from Function, snip]

Canvas.Context2d             Canvas.Image                 Canvas.ImageData             Canvas.JPEGStream
Canvas.PNGStream             Canvas.cairoVersion          Canvas.prototype             Canvas.version

// 2.0 pre-this PR also had Canvas.backends

The constructors are useful at least for instanceof (although Context2d should be CanvasRenderingContext2d), and cairoVersion/version have their merits as well. Maybe go back to exposing all of those, and just additionally export the create* and loadImage functions?

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Sounds like that was the intent actually:

I want to keep new Image() since that does indeed work in the browser.

• Move non-standard API out of the Canvas class #833 (comment)

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Edit 3: Plus exposing all the original constructors means that all of the examples and benchmarks won't need to be updated, and legacy code will continue to work :)