image-raub/README.md

Native Image loader for Node.js

# Image for Node.js

This is a part of [Node3D](https://github.com/node-3d) project.

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```console
npm i -s image-raub
```

Using [FreeImage](http://freeimage.sourceforge.net/), this addon loads images from:
* Local file.
* Data URI.
* Http(s) URL.
* Node.js Blob URL.
* Raw RGBA pixel data.

The Image class is similar to
[HTMLImageElement](https://developer.mozilla.org/en-US/docs/Web/API/HTMLImageElement/Image),
and can be used as a replacement in non-DOM environments.

Additional features:
* `save` - saves the image to a local file.
* `drawImage` - is similar to
	[drawImage](https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawImage).

> Note: this **addon uses N-API**, and therefore is ABI-compatible across different
Node.js versions. Addon binaries are precompiled and **there is no compilation**
step during the `npm i` command.


## Image

```js
import Image from 'image-raub';
const image = new Image('images/test.png'); // relative to CWD
icon.on('load', () => { console.log('data', image.width, image.height, image.data); });
```

For loaded images, `image.data` will contain a `Buffer` of `4 * width * height` bytes.
You can directly interact with that buffer - read or write, and then save the image
to a file or use it any other way.

With `Image.fromPixels()` it is possible to generate new images from scratch by providing
your own data buffer.

See [TS declarations](/index.d.ts) for more details.


### Set window icon

Compatible with [glfw-raub](https://github.com/node-3d/glfw-raub) `window.icon` property.

```js
const icon = new Image();
icon.src = 'icons/logo.png';
icon.on('load', () => { window.icon = icon; });
```


### Load an OpenGL texture

Here `Image` is used to load a texture. The constructed object receives `src` property,
then the file is read and `'load'` event is emitted. After that, `image.data` is
available as a `Buffer`, containing the whole pixel data, and `image.width`/`image.height`
contain the dimensions.

```js
const Image = require('image-raub');
const image = new Image();
// Web-style onload
image.onload = () => {
	gl.bindTexture(gl.TEXTURE_2D, texture);
	gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR_MIPMAP_NEAREST);
	gl.generateMipmap(gl.TEXTURE_2D);
	gl.bindTexture(gl.TEXTURE_2D, null);
};

image.src = 'textures/grass.jpg';
```


### Make an OpenGL snapshot

Image can save its current content to the filesystem. It can also load from raw
pixel values using `static fromPixels()` method.

```js
const memSize = screen.w * screen.h * 4; // estimated number of bytes
const storage = { data: Buffer.allocUnsafeSlow(memSize) };

gl.readPixels(
	0, 0,
	screen.w, screen.h,
	gl.RGBA,
	gl.UNSIGNED_BYTE,
	storage
);

const img = Image.fromPixels(screen.w, screen.h, 32, storage.data);

img.save(`${Date.now()}.jpg`);
```