Add raw image support

[basvanmeurs]

When you need to read parsed raw ARGB image data, you need to load the image, then draw it on a canvas and convert it to a buffer:

    var img = new Canvas.Image();
    img.src = data;
    var canvas = new Canvas(img.width, img.height);
    var ctx = canvas.getContext('2d');
    ctx.drawImage(img, 0, 0, img.width, img.height);
    var buffer = canvas.toBuffer('raw');

This is an unnecessary double copy of the data. This pull request contains a new method: Image.getRawData, which returns the buffer directly:

    var img = new Canvas.Image();
    img.src = data;
    var buffer = img.getRawData();

This allows for a more efficient usage of Canvas.Image.

We'd appreciate it if you'd merge this into the node-canvas module!

[zbjornson]

Looks good. Needs a conflict fixed again (sorry), and ideally one trivial change.

I can make the changes real quick if you want.

[LinusU]

Would prefer to have this as a guard instead, e.g.

if (!img->_surface) {
  info.GetReturnValue().Set(Nan::Undefined());
  return;
}

// ...

[LinusU]

No need to return at the end of the function ☺️

[zbjornson]

Also don't need the else { set undefined } block -- that's implicit if you didn't set another return value.

[LinusU]

Please follow standard style here (2 spaces indentation, space between function and (), no semicolons)

[LinusU]

Personally not a fan of tacking more non-standard things on to the prototype 🤔 I do see the use case though.

Generally, what do we think about having these as standalone exported functions? Not sure that this is a good idea, but it could be something like this:

const { getRawImageBuffer } = require('canvas')

// img = ...
const buffer = getRawImageBuffer(img)

Just a thought 🤔 💭

[basvanmeurs]

Can you please re-consider bringing this in to node-canvas, or explain what needs to be done exactly to get it in there?

[basvanmeurs]

Hi guys, can you spare some time to review and consider merge please?

[zbjornson]

I don't mind if this goes on the prototype or is an accessory function. It's slightly more convenient on the prototype (one less function to import), but agree with @LinusU that we should avoid adding more non-standard methods. I defer to others' decisions.

A few of Linus's comments are still pending though, and the last commit should be removed (CI forces a build from source).

[LinusU]

I defer to others' decisions.

I feel the same 😁

The comments need to be addressed before we merge though...

[NightScript370]

I just sent a Pull Request addressing the comments