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README.md

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

  1. git clone this repo: git clone git@github.com:yahoo/gifshot.git
  2. Install Node.js
  3. Install all local dependencies: npm install
  4. Start up the included node.js preview server: npm run preview
  5. 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);
  }
});

Images With Frame-Specific Text

gifshot.createGIF({
  'images': [
    { src:'http://i.imgur.com/2OO33vX.jpg', text:'First image text' },
    { src:'http://i.imgur.com/qOwVaSN.png', text:'Second image text' },
    { src:'http://i.imgur.com/Vo5mFZJ.gif', text:'Third image text' }
  ]
},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,
// CSS filter that will be applied to the image (eg. blur(5px))
'filter': '',
// The amount of time (in seconds) to wait between each frame capture
'interval': 0.1,
// The amount of time (in seconds) to start capturing the GIF (only for HTML5 videos)
'offset': null,
// The number of frames to use to create the animated GIF
// Note: Each frame is captured every 100 milliseconds of a video and every ms for existing images
'numFrames': 10,
// The amount of time (10 = 1s) to stay on each frame
'frameDuration': 1,
// 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': [],
// When existing images or videos are requested used, we set a CORS attribute on the request.
// Options are 'Anonymous', 'use-credentials', or a falsy value (like '') to not set a CORS attribute.
'showFrameText': true,
// If frame-specific text is supplied with the image array, you can force the frame-specific text to not be displayed
// by making this option 'false'.
'crossOrigin': 'Anonymous',
waterMark: null,
// If an image is given here, it will be stamped on top of the GIF frames
waterMarkHeight: null,
// Height of the waterMark
waterMarkWidth: null,
// Height of the waterMark
waterMarkXCoordinate: 1,
// The X (horizontal) Coordinate of the watermark image
waterMarkYCoordinate: 1
// The Y (vertical) Coordinate of the watermark image

Contributing

Please send all PR's to the dev branch.

If your PR is a code change:

  1. Install all node.js dev dependencies: npm install
  2. Update the appropriate module inside of the src/modules directory.
  3. Install gulp.js globally: sudo npm install gulp -g
  4. Build, Test, and Minify gifshot with Gulp: gulp
  5. Verify that the minified output file has been updated in dist/gifshot.js and dist/gifshot.min.js and that no unit tests are failing.
  6. 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

  • 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.
  • Copyright (c) Anthony Dekker 1994 - MIT License
  • Encodes a GIF into the GIF89 spec
  • Copyright (c) Dean McNamee, 2013 - MIT License

Inspiration

  • A module wrapping WebRTC's getUserMedia
  • Uses web workers and encoding/decoding algorithms to produce a Base 64 data URI image

Contributors

Chase West

Greg Franko

Chris Chernoff

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