canvid

canvid.js

canvid is a tiny dependency free library for playback of relatively short videos on canvas elements.

• Why not just use HTML5 video?
  Because you can't embed and autoplay HTML5 videos on iOS! Yeah, that sucks.

• Why is this better than using an animated GIF?
  Videos look kind of gross when converted to animated GIFs because of the colors sampling. Also the file size of video GIFs can get pretty huge. GIF is just not made for videos. JPG does a much better job of compressing video frames. Also, animated GIFs don't give you any playback controls. You can't pause a GIF or delay it's playback. With canvid you can do that.

• Why only "relatively short" videos?
  As you see further down, the container format for canvid is a big image sprite of all the frames of each clip. Sadly, iOS limits the maximum image size (bigger image get sampled down), so that puts a limit on the maximum frames you can store.

• Why is there no audio?
  canvid doesn't support audio for the same reason animated GIF doesn't support audio either: because that's not what it was built for.

Installation

npm

$ npm install --save canvid

git clone

$ git clone [e-mail]:gka/canvid.git

Usage

You can use canvid.js with AMD, CommonJS and browser globals.

var canvidControl = canvid({
    selector : '.video',
    videos: {
        clip1: { src: 'clip1.jpg', frames: 38, cols: 6, loops: 1, onEnd: function(){
          console.log('clip1 ended.');
          canvidControl.play('clip2');
        }},
        clip2: { src: 'clip2.jpg', frames: 43, cols: 6, fps: 24 }
    },
    width: 500,
    height: 400,
    loaded: function() {
        canvidControl.play('clip1');
        // reverse playback
        // canvidControl.play('clip1', true);
    }
});

If you want to use canvid with React you can check this simple react + canvid demo to see how it works.

Options

• videos required
  Video/Sprite objects (videoKey : videoOptions).

  • src required
    Path of the sprite image.

  • frames required
    Number of frames.

  • cols required
    Number of columns.

  • loops optional
    Number of loops.

  • fps optional (default: 15)
    Frames per second.

  • onEnd optional
    Function that gets called when the clip ended.

• selector optional
  The selector of the element where the video gets displayed. You can also pass a DOM element as a selector. default: '.canvid-wrapper'

• width optional
  Width of the element where the video gets displayed.
  default: 800

• height optional
  Height of the element where the video gets displayed.
  default: 450

• loaded optional
  Function that gets called when all videos are loaded.

• srcGif optional
  Path of the fallback gif, if canvas is not supported.

Methods

The canvid function returns an object to control the video:

var canvidControl = canvid(canvidOptions);

play
Plays video of the passed videoKey. The parameters isReverse (default: false) and fps (default: 15) are optional.

canvidControl.play(videoKey [,isReverse, fps]);

pause
Pause current video.

canvidControl.pause();

resume
Resume current video.

canvidControl.resume();

destroy
Stops video and removes the canvas of the current canvid element from the DOM.

canvidControl.destroy();

isPlaying
Returns true or false whether the video is playing or not.

canvidControl.isPlaying();

getCurrentFrame
Returns the current frame number.

canvidControl.getCurrentFrame();

setCurrentFrame
Sets the current frame number.

canvidControl.setCurrentFrame(0);

How to convert your video to a JPG sprite

First, convert you video into single frames using ffmpeg:

mkdir frames
ffmpeg -i myvideo.mp4 -vf scale=375:-1 -r 5 frames/%04d.png

Then, use ImageMagicks montage to stich all the frames into one big image:

montage -border 0 -geometry 375x -tile 6x -quality 60% frames/*.png myvideo.jpg

Is canvid responsive?

Yes it is, thanks to a nice little trick. Regardless of what width and height parameters you set in the canvid constructor, you can use style="width:100%" on the canvas element and it will get scaled to the outer container and preserve its original aspect ratio.

canvas.canvid {
  width: 100%;
}

Known Issues

Some users encountered problems on mobile devices with large sprites. A workaround is to split the sprite into multiple sprites.

If you're experiencing problems with montage (e.g. "unable to read font") try updating imagemagick to the latest version.

Contributors

• Gregor Aisch
• Moritz Klack