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glitch-canvas

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glitch-canvas

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$ bower install glitch-canvas

$ npm install glitch-canvas

what is it?

glitch-canvas is a javascript library for applying a glitch effect to a canvas element. it can be used to transform images to look like this:

glitched image

for a live example, you can check out my jpg-glitch editor online.

how to use it

this library can be used in web browsers as well as in node. it supports loading as an AMD module, as a CommonJS module or a global variable..

a simple example:

    glitch( { seed: 25, quality: 30 } )
        .fromImage( image )
        .toDataURL()
        .then( function( dataURL ) {
            var glitchedImg = new Image();
            glitchedImg.src = dataURL;
        } );

as you can see, there are three calls happening:

  1. glitch() is called with the glitch parameters
  2. then fromImage() is called with the input image as parameter
  3. and finally toDataURL() is called to output a dataURL.

when using the library, always follow these three steps:

  1. glitch
  2. input
  3. output

all input and output methods are asynchronous and use promises for flow control.

for an explanation of all available methods and parameters, check out the reference section below.

you can find more examples for both node and the browser in the examples folder of this repository.

reference

glitch()

glitch() can take the following parameters that control how the glitched image is going to look:

 
// the parameters listed are the default params 
 
var glitchParams = {
    seed:       25, // integer between 0 and 99 
    quality:    30, // integer between 0 and 99 
    amount:     35, // integer between 0 and 99 
    iterations: 20  // integer 
};
 

it returns an object containing all input methods.

fromImage()

fromImage() expects an Image object as its only parameter. it returns an object containing all input methods.

example:

var image = new Image();
 
image.onload = function () {
    glitch()
        .fromImage( image )
        .toDataURL()
        .then( function( dataURL ) {
            var glitchedImg = new Image();
            glitchedImg.src = dataURL;
            document.body.appendChild( glitchedImg );
        } );
};
 
image.src = 'lincoln.jpg'

please note: this method is not available in node. important: when using the library in a browser, make sure the image was loaded before glitching it.

fromImageData()

fromImageData() expects an ImageData object as its only parameter. it returns an object containing all input methods.

example:

var canvas = document.createElement( 'canvas' );
var ctx = canvas.getContext( '2d' );
 
ctx.fillStyle = 'red';
ctx.fillRect( 30, 30, 90, 45 );
ctx.fillStyle = 'green';
ctx.fillRect( 10, 20, 50, 60 );
 
var imageData = ctx.getImageData( 0, 0, canvas.width, canvas.height );
 
glitch()
    .fromImageData( imageData )
    .toDataURL()
    .then( function( dataURL ) {
        var glitchedImg = new Image();
        glitchedImg.src = dataURL;
        document.body.appendChild( glitchedImg );
    } );

fromBuffer()

fromBuffer() expects a Buffer object as its only parameter. it returns an object containing all input methods.

it uses image#src=buffer from node-canvas internally.

example:

var fs = require('fs');
 
fs.readFile( './lincoln.jpg', function ( err, buffer ) {
    if ( err ) { throw err; }
        
    glitch()
        .fromBuffer( buffer )
        .toBuffer()
        .then( function ( glitchedBuffer ) {
            fs.writeFile( __dirname + '/glitched-lincoln.png', glitchedBuffer, function ( err ) {
                if ( err ) { throw err; }
                console.log( 'file glitched.' );
            } );
        } );
} );

please note: this method is only available in node.

fromStream()

fromStream() expects a ReadableStream object as its only parameter. it returns an object containing all input methods.

it uses image#src=buffer from node-canvas internally.

example:

var fs = require('fs');
 
var inputStream = fs.createReadStream( './lincoln.jpg' );
var outputStream = fs.createWriteStream( './glitched-lincoln.png' );
 
glitch()
    .fromStream( inputStream )
    .toPNGStream()
    .then( function ( pngStream ) {
        pngStream.on( 'data', function ( chunk ) { outputStream.write( chunk ); } );
        pngStream.on( 'end', function () { console.log( 'png file saved.' ); } );
    } );

please note: this method is only available in node. currently, theres no input sanitation for this method, so you'll want to make sure that the input stream contains an image.

toDataURL()

toDataURL() does not take any parameters. it returns a String containing the base64-encoded image url.

example:

var image = new Image();
 
image.onload = function () {
    glitch()
        .fromImage( image )
        .toDataURL()
        .then( function( dataURL ) {
            var glitchedImg = new Image();
            glitchedImg.src = dataURL;
            document.body.appendChild( glitchedImg );
        } );
};
 
image.src = 'lincoln.jpg'

toImageData()

toImageData() does not take any parameters. it returns an ImageData object.

example:

var image = new Image();
 
image.onload = function () {
    glitch()
        .fromImage( image )
        .toImageData()
        .then( function ( imageData ) {
            var canvas = document.createElement( 'canvas' );
            var ctx = canvas.getContext( '2d' );
            ctx.putImageData( imageData, 0, 0 );
 
            document.body.appendChild( canvas );
        } );
};
 
image.src = 'lincoln.jpg'

toImage()

toImage() does not take any parameters. it returns an Image object.

example:

var image = new Image();
 
image.onload = function () {
    glitch()
        .fromImage( image )
        .toImage()
        .then( function ( glitchedImage ) {
            document.body.appendChild( glitchedImage );
        } );
};
 
image.src = 'lincoln.jpg'

please note: this method is only available in the browser.

toBuffer()

toBuffer() doesn't take any parameters. it uses canvas#tobuffer from node-canvas internally.

it returns a Buffer object.

example:

var fs = require('fs');
 
fs.readFile( './lincoln.jpg', function ( err, buffer ) {
    if ( err ) { throw err; }
        
    glitch()
        .fromBuffer( buffer )
        .toBuffer()
        .then( function ( imageBuffer ) {
            fs.writeFile( './glitched-lincoln.png', imageBuffer, function ( err ) {
                if ( err ) { throw err; }
                console.log( 'created a pdf file.' );
            } );
        } );
} );

please note: this method is only available in node.

toJPGStream()

toJPGStream() can take the following parameters:

var jpgStreamParams = {
    bufsize: 4096,          // output buffer size in bytes 
    quality: 75,            // jpg quality (0-100) default: 75 
    progressive: false      // true for progressive compression 
};
 

it uses canvas#jpegstream() from node-canvas internally.

it returns a JPEGStream object.

example:

var fs = require('fs');
fs.readFile( __dirname + '/lincoln.jpg', function ( err, buffer ) {
        if ( err ) {
            throw err;
        }
 
        var fileStream = fs.createWriteStream( __dirname + '/glitched-lincoln.jpg' );
        
        glitch()
            .fromBuffer( buffer )
            .toJPGStream()
            .then( function ( jpgStream ) {
                jpgStream.on( 'data', function ( chunk ) { fileStream.write( chunk ); } );
                jpgStream.on( 'end', function () { console.log( 'file glitched.' ); } );
            } );
    } );

please note: this method is only available in node.

toJPEGStream()

see toJPGStream().

toPNGStream()

toPNGStream() doesn't take any parameters. it uses canvas#pngstream() from node-canvas internally.

it returns a PNGStream object.

example:

var fs = require('fs');
fs.readFile( __dirname + '/lincoln.jpg', function ( err, buffer ) {
        if ( err ) { throw err; }
 
        var fileStream = fs.createWriteStream( __dirname + '/glitched-lincoln.png' );
        
        glitch()
            .fromBuffer( buffer )
            .toPNGStream()
            .then( function ( pngStream ) {
                pngStream.on( 'data', function ( chunk ) { fileStream.write( chunk ); } );
                pngStream.on( 'end', function () { console.log( 'file glitched.' ); } );
            }, function( err ) {
                console.log( 'There was an error', err );
            } );
    } );

please note: this method is only available in node.

development

npm run build will build the node-ready and browser-ready versions, which are saved to the dist-node and dist directories.

npm run test will run the tests in both the browser and node.

you can find the source code for the library in the src folder. it is using es6-style syntax.

license

mit

third party code

most of the folder structure and the npm script setup were taken from nonalnawson's hello javascript repo (Apache-2.0 license).

dependencies:

glitch-canvas in the wild

implementations in other languages

if you want to add your site or project to one of these lists, you can create a pull request or send me an email.

missing somehing?

found a bug? missing a feature? instructions unclear? are you using this library in an interesting project? maybe have a look at the issues, open a pull request and let me know. thanks!

most importantly

thank you for taking a look at this repo. have a great day :)