image-raub

Image for Node.js

This is a part of Node3D project.

npm i image-raub

Synopsis

Node.js N-API addon implementing the HTMLImageElement.

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.

The src property can be:

• A local file.
• A data URI.
• A http(s) URL.

FreeImage is used as backend decoder.

Additional features include:

• Save the image to disk.
• Create an Image from raw RGBA pixel data.
• Some context 2d functionality, e.g. drawImage.

Usage

Load an OpenGL texture

const Image = require('image-raub');
const image = new Image();
// Web-style onload
image.onload = () => {
	gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
	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 = `${__dirname}/texture.jpg`;

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.

Make an OpenGL snapshot

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`);

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

Properties

• get/set number width/naturalWidth - image width.
• get/set number height/naturalHeight - image height.
• get/set [width, height] wh - image width and height.
• get/set {width, height} size - image width and height.
• get/set string src - image source file.
• get/set function onload - setter uses .on('load', ...) method, getter returns all listeners.
• get/set function onerror - setter uses .on('error', ...) method, getter returns all listeners.
• get boolean complete - if image has already been loaded.

Methods:

• save(string dest) - save Image to file. Resize to w, h is optional.
• drawImage(src, ...) - refer to drawImage, but optional params dx, dy are ignored.
• load(Buffer data) - load from a file in memory.
• static fromPixels(uint width, uint height, uint bpp, Buffer pixels) - create image from raw pixels. For example it helps when you want to store the result of glReadPixels() as an image.

Events:

• 'load' - the requested (src) file was loaded.
• 'error' - an error has occured.