gifshot: A JavaScript repository from tianwalker2012

JavaScript library that can create animated GIFs from media streams, videos, or images

How

gifshot uses the following technologies:

The webRTC getUserMedia() API to get permission to use a user's webcam and manipulate the CameraStream Media object
The HTML5 Filesystem APIs to handle the temporary blob URL creation
The HTML5 video element to stream the blob URL
The canvas API to create a dynamic image from an HTML5 video, or images
Web workers to process the GIF frames
Typed Arrays to handle binary image data
Base 64 encoding to create a base 64 encoded image string

Browser Support

Animated GIF from Webcam :

Firefox 17+, Chrome 21+, Opera 18+, Blackberry Browser 10+, Opera Mobile 12+, Chrome For Android 35+, Firefox for Android 29+

Animated GIF from Existing Video :

All modern browsers (IE10+)

Animated GIF from Existing Images :

All modern browsers (IE10+)

Quick Start

Include gifshot on your HTML page (gifshot.js can be found in the build directory)

<script src='gifshot.js'></script>

Start using the JavaScript API to create your animated GIFs

// By default, a user's webcam is used to create the animated GIF
gifshot.createGIF({}, function(obj) {
	if(!obj.error) {
		var image = obj.image,
		animatedImage = document.createElement('img');
		animatedImage.src = image;
		document.body.appendChild(animatedImage);
	}
});

Demo Set Up

git clone this repo: git clone https://git.corp.yahoo.com/sports/gifshot.git
Install Node.js
Install all local dependencies: npm install
Start up the included node.js preview server: npm run preview
Go to localhost:8001 to try out gifshot

API Methods

createGIF(options, callback)

Creates an animated GIF from either a webcam stream, an existing video (e.g. mp4), or existing images

Note: If you wish to use the default options, you can just pass a callback function as the only argument

Another Note: An object is passed back to the callback function with helpful data

gifshot.createGIF({}, function(obj) {
	// callback object properties
	// --------------------------
	// image - Base 64 image
	// cameraStream - The webRTC MediaStream object
	// error - Boolean that determines if an error occurred
	// errorCode - Helpful error label
	// errorMsg - Helpful error message
	// savedRenderingContexts - An array of canvas image data (will only be set if the saveRenderingContexts option was used)
});

takeSnapShot(options, callback)

Takes a snap shot (not animated) image from a webcam stream or existing video

Note: If you wish to use the default options, you can just pass a callback function as the only argument

Another Note: An object is passed back to the callback function with helpful data

gifshot.takeSnapShot({}, function(obj) {
	// callback object properties
	// --------------------------
	// image - Base 64 image
	// error - Boolean that determines if an error occurred
	// errorCode - Helpful error label
	// errorMsg - Helpful error message
	// savedRenderingContexts - An array of canvas image data (will only be set if the saveRenderingContexts option was used)
});

stopVideoStreaming()

Turns off the user's webcam (by default, the user's webcam is turned off)

Note: This is helpful when you use the keepCameraOn option

gifshot.stopVideoStreaming();

isSupported()

If the current browser supports all of the gifshot animated GIF options

gifshot.isSupported();

isWebCamGIFSupported()

If the current browser supports creating animated GIFs from a webcam video stream

gifshot.isWebCamGIFSupported();

isExistingVideoGIFSupported()

If the current browser supports creating animated GIFs from an existing HTML video (e.g. mp4, ogg, ogv, webm)

Note: You can pass in an array of codec extensions to specifically check if the current browser supports at least one of them

gifshot.isExistingVideoGIFSupported(['mp4', 'ogg']);

isExistingImagesGIFSupported()

If the current browser supports creating animated GIFs from existing images (e.g. jpeg, png, gif)

gifshot.isExistingImagesGIFSupported();

Examples

Web Cam

gifshot.createGIF(function(obj) {
	if(!obj.error) {
		var image = obj.image,
		animatedImage = document.createElement('img');
		animatedImage.src = image;
		document.body.appendChild(animatedImage);
	}
});

HTML5 Video

gifshot.createGIF({
	'video': ['example.mp4', 'example.ogv']
},function(obj) {
	if(!obj.error) {
		var image = obj.image,
		animatedImage = document.createElement('img');
		animatedImage.src = image;
		document.body.appendChild(animatedImage);
	}
});

Images

gifshot.createGIF({
	'images': ['http://i.imgur.com/2OO33vX.jpg', 'http://i.imgur.com/qOwVaSN.png', 'http://i.imgur.com/Vo5mFZJ.gif']
},function(obj) {
	if(!obj.error) {
		var image = obj.image,
		animatedImage = document.createElement('img');
		animatedImage.src = image;
		document.body.appendChild(animatedImage);
	}
});

Snap Shot

gifshot.takeSnapShot(function(obj) {
	if(!obj.error) {
		var image = obj.image,
		animatedImage = document.createElement('img');
		animatedImage.src = image;
		document.body.appendChild(animatedImage);
	}
});

Options

// Desired width of the image
'gifWidth': 200,
// Desired height of the image
'gifHeight': 200,
// If this option is used, then a GIF will be created using these images
// e.g. ['http://i.imgur.com/2OO33vX.jpg', 'http://i.imgur.com/qOwVaSN.png', 'http://i.imgur.com/Vo5mFZJ.gif'],
// Note: Make sure these image resources are CORS enabled to prevent any cross-origin JavaScript errors
// Note: You may also pass a NodeList of existing image elements on the page
'images': [],
// If this option is used, then a gif will be created using the appropriate video
// HTML5 video that you would like to create your animated GIF from
// Note: Browser support for certain video codecs is checked, and the appropriate video is selected
// Note: You may also pass a NodeList of existing video elements on the page
// e.g. 'video': ['example.mp4', 'example.ogv'],
'video': null,
// You can pass an existing video element to use for the webcam GIF creation process,
// and this video element will not be hidden (useful when used with the keepCameraOn option)
// Pro tip: Set the height and width of the video element to the same values as your future GIF
// Another Pro Tip: If you use this option, the video will not be paused, the object url not revoked, and
// the video will not be removed from the DOM.  You will need to handle this yourself.
'webcamVideoElement': null,
// Whether or not you would like the user's camera to stay on after the GIF is created
// Note: The cameraStream Media object is passed back to you in the createGIF() callback function
'keepCameraOn': false,
// Expects a cameraStream Media object
// Note: Passing an existing camera stream will allow you to create another GIF and/or snapshot without
//	asking for the user's permission to access the camera again if you are not using SSL
'cameraStream': null,
// The amount of time (in seconds) to wait between each frame capture of a video
'interval': 0.1,
// The number of frames to use to create the animated GIF
// Note: Each frame is captured every 100 milleseconds of a video
'numFrames': 10,
// The text that covers the animated GIF
'text': '',
// The font weight of the text that covers the animated GIF
'fontWeight': 'normal',
// The font size of the text that covers the animated GIF
'fontSize': '16px',
// The minimum font size of the text that covers the animated GIF
// Note: This option is only applied if the text being applied is cut off
'minFontSize': '10px',
// Whether or not the animated GIF text will be resized to fit within the GIF container
'resizeFont': false,
// The font family of the text that covers the animated GIF
'fontFamily': 'sans-serif',
// The font color of the text that covers the animated GIF
'fontColor': '#ffffff',
// The horizontal text alignment of the text that covers the animated GIF
'textAlign': 'center',
// The vertical text alignment of the text that covers the animated GIF
'textBaseline': 'bottom',
// The X (horizontal) Coordinate of the text that covers the animated GIF (only use this if the default textAlign and textBaseline options don't work for you)
'textXCoordinate': null,
// The Y (vertical) Coordinate of the text that covers the animated GIF (only use this if the default textAlign and textBaseline options don't work for you)
'textYCoordinate': null,
// Callback function that provides the current progress of the current image
'progressCallback': function(captureProgress) {},
// Callback function that is called when the current image is completed
'completeCallback': function() {},
// how many pixels to skip when creating the palette. Default is 10. Less is better, but slower.
// Note: By adjusting the sample interval, you can either produce extremely high-quality images slowly, or produce good images in reasonable times.
// With a sampleInterval of 1, the entire image is used in the learning phase, while with an interval of 10,
// a pseudo-random subset of 1/10 of the pixels are used in the learning phase. A sampling factor of 10 gives a
// substantial speed-up, with a small quality penalty.
'sampleInterval': 10,
// how many web workers to use to process the animated GIF frames. Default is 2.
'numWorkers': 2,
// Whether or not you would like to save all of the canvas image binary data from your created GIF
// Note: This is particularly useful for when you want to re-use a GIF to add text to later
'saveRenderingContexts': false,
// Expects an array of canvas image data
// Note: If you set the saveRenderingContexts option to true, then you get the savedRenderingContexts
//	in the createGIF callback function
'savedRenderingContexts': []

Custom Builds

We provide a gulp custom-build task, that allows you to remove certain dependencies that you may not need. Pass in the custom build name that you would like (it default to webcam):

gulp custom-build --webcam

Note: For custom builds, you need to clone this repo locally. Also, the unminified and minified custom build files will be in the build/custom directory of the local gifshot repo.

###Possible build options:

webcam - The webcam-to-GIF functionality of gifshot (the existing image/video logic is removed)

image - The image-to-GIF functionality of gifshot (the existing webcam/video logic is removed)

video - The HTML5 video-to-GIF functionality of gifshot (the existing webcam/image logic is removed)

Contributing

Please send all PR's to the dev branch.

If your PR is a code change:

Install all node.js dev dependencies: npm install
Update the appropriate module inside of the src/modules directory.
Install gulp.js globally: sudo npm install gulp -g
Concatenate, Lint, Test, and Minify gifshot with Gulp: gulp
Verify that the minified output file has been updated in build/gifshot.js and build/gifshot.min.js and that no unit tests are failing.
Send the PR!

Note: There is a gulp watch task set up that will automatically build, test, and minify gifshot whenever a module inside of the src/modules directory is changed. We recommend using it.

Credits

gifshot would not have been possible without the help/inspiration of the following libraries/awesome people:

###Used

NeuQuant

An image quantization algorithm to reduce the number of colors required to represent the image (thus decreasing the file size). This script was ported from C into Java by Kevin Weiner and then to ActionScript 3 by Thibault Imbert, and to JavaScript by antimatter15, and fixed, patched and revised by sole.

Dean McNamee's omggif

Encodes a GIF into the GIF89 spec

###Inspiration

Soledad Penadés's gumhelper.js

A module wrapping WebRTC's getUserMedia

Soledad Penadés's animated_GIF.js

Uses web workers and encoding/decoding algorithms to produce a Base 64 data URI image

Jen Fong-Adwent's (aka Edna Piranha) Meatspace Chat

tianwalker2012/gifshot

How