Filterous 2

Filterous 2 is an Instagram-like image manipulation library for Javascript and node.js.

This is a revamped version of Filterous, which was written for JavaScript for browser about 4 years ago. This version works on both Node.js and browser, and comes with pre-defined Instagram-like filters (with the same filter names and very similar effects).

Installation

For Node.js:

first, this module uses node-canvas, so you need Cairo and Pango. Please follow the installation guide here before started.

$ npm install filterous

For Browser:

<script src="filterous2.min.js"></script>

The minified JavaScript code is available on Release page.

Usage

The usages are slightly different for Node.js and the browser.

Basic Usage for Node.js

Import an image buffer to filterous then save to the disk.

const filterous = require('filterous');

filterous.importImage(buffer, options)
  .applyFilter(filter, value)
  .save(filename);

also:

filterous.importImage(buffer)
  .applyInstaFilter(filterName, options)
  .save(filename);

The applyFilter() can be used with other filters and the results are accumulative, while the predefined applyInstaFilter() overwrite the previous filter result. However you can use applyFilter() to adjust the colors after applyInstaFilter() is applied.

Options are:

{
  scale: <value>, 
  format: <imageFormat> 
}

The value must be less than 1. You can only scale down an image. and the imageFormat is either 'png', 'gif', or 'jpeg' (default).

Example for Node.js

Using color adjustment filters:

fs.readFile('input/leia.jpg', (err, buffer) => {
  if (err) throw err;
  let f = filterous.importImage(buffer)
    .applyFilter('brightness', 0.2)
    .applyFilter('colorFilter', [255, 255, 0, 0.05])
    .save('output/leia.jpg');
});

Example with predefined Instagram-like effects:

fs.readFile('input/leia.jpg', (err, buffer) => {
  let f = filterous.importImage(buffer, {scale: 0.5, format: 'png'})
    .applyInstaFilter('amaro')
    .save('output/leia.jpg');
});

Basic Usage for JavaScript on Browser

Import an image object to filterous and render as HTML with renderHtml.

filterous.importImage(imgObj, options)
  .applyFilter(filter, value)
  .renderHtml(imageDOM);

also:

filterous.importImage(imgObj, options)
  .applyInstaFilter(filterName)
  .renderHtml(imageDOM);

var imageDOM = document.querySelector('img.photo');
var imgObj = new Image();
imgObj.src = 'input/leia.jpg';

filterous.importImage(imgObj, options)
  .applyFilter('brightness', 0.2)
  .applyFilter('contrast', -0.3)
  .renderHtml(imageDOM);

Example with predefined Instagram-like effects:

filterous.importImage(imgObj, options)
  .applyInstaFilter(filterButton.id)
  .renderHtml(imageDOM);

Available Filter Effects and the Values

Most effects take a value (the amount of the effects) between -1 and 1. for example, the value for the brightness() 0 means unchanged, -1 darkens the image, and 1 means full-brightness. The image will turn almost completely white.

Effect	Adjestment(s)
grayscale	N/A
sepia	0 to 1
invert	N/A
brightness	-1 to 1
saturation	-1 to 1
contrast	-1 to 1
rgbAdjust	[r, g, b]
colorFilter	[r, g, b, adj] // adj is 0 to 1
convolute	3x3 matrix

Available InstaFilter Names

Names
normal	clarendon	gingham	moon	lark	reyes
juno	slumber	crema	ludwig	aden	perpetua
amaro	mayfair	rise	hudson	valencia	xpro2
sierra	willow	lofi	inkwell	hefe	nashville
stinson	vesper	earlybird	brannan	sutro	toaster
walden	1977	kelvin	maven	ginza	skyline
dogpatch	brooklyn	helena	ashby	charmes

Note: normal gives no filter effect. It normalize the image to the original.

Demo

Try the demo on browser!

Behind the Scene

Filterous takes an image into a canvas to manipulate the pixels of the image. Unlike the CSS filters that alters how the image appearance only on browsers, the JavaScript library actually alters the pixel color values. So you can actually download the modified image.

The CanvasRenderingContext.getImageData() method of the Canvas API returns an ImageData object representing the underlying pixel data of the canvas, and the data property of pixelData stores the color info of an each pixel in the canvas. (The diagram below shows a canvas size of only 9x9 pixel to make it simple).

Each pixel in the data array consists of 4 bytes values- red, green, blue, and alpha channel, and each of the R (red), G (green), B (blue) and A (alpha transparency) values can take values between 0 and 255.

This library alters R, G, or B values of each pixel (yes, each pixel in the entire image! so the operation can be quite slow with JavaScript!) to get filtered look.

Browser Supports

Filterous 2 for browsers should support all the modern browsers that supports Promises.

Contribute

I am pretty sure this library is buggy. Please feel free to send me pull requests.