somewhere to talk about random ideas and projects like everyone else



Onion Skinning in Ajax Animator 01 March 2010

The Ajax Animator (Wave/Mini interface version) now has support for basic Onion skinning, where the last keyframe is semitransparently placed in the background to aid in the positioning of the next keyframe. It’s now enabled by default at 20% opacity but can be disabled.

To disable it, click the advanced button on the right side of the toolbar and find the entry labeled Onion Skinning, there you can set the onion skinning opacity or disable it with 0% opacity.

Pure JavaScript HTML5 <canvas> to (Animated) GIF Conversion 03 January 2010

Based on as3gif Ported by antimatter15

This is the raw canvas element saved as a non-animated PNG
This is the GIF which was generated from the canvas.
This is the GIF which was generated from the canvas.

AS3GIF lets you play and encode animated GIF’s with ActionScript 3

Since web pages can usually natively play GIFs fine, it’s only a port of the GIFEncoder portions of the library.

Basic Usage

Since it pretty much is GIFEncoder, you could consult the as3gif how-to page

But there are some differences so I’ll cover it here anyway.

You first need to include the JS files. It’s probably best if you include it in this order, but it shouldn’t matter too much.

<script type="text/javascript" src="LZWEncoder.js"></script>
<script type="text/javascript" src="NeuQuant.js"></script>
<script type="text/javascript" src="GIFEncoder.js"></script>

If you want to render the gif through an inline <img> tag or try to save to disk or send to server or anything that requires conversion into a non-binary string form, you should probably include b64.js too.

<script type="text/javascript" src="b64.js"></script>

Simple enough right? Now to convert stuff to GIF, you need to have a working <canvas> or at least some imageData-esque array.

<canvas id="bitmap"></canvas>
  var canvas = document.getElementById('bitmap');
  var context = canvas.getContext('2d');
  context.fillStyle = 'rgb(255,255,255)';
  context.fillRect(0,0,canvas.width, canvas.height); //GIF can't do transparent so do white

  context.fillStyle = "rgb(200,0,0)";  
  context.fillRect (10, 10, 75, 50);   //draw a little red box

Now we need to init the GIFEncoder.

  var encoder = new GIFEncoder();

If you are making an animated gif, you need to add the following

  encoder.setRepeat(0); //0  -> loop forever
                        //1+ -> loop n times then stop
  encoder.setDelay(500); //go to next frame every n milliseconds

Now, you need to tell the magical thing that you’re gonna start inserting frames (even if it’s only one).


And for the part that took the longest to port: adding a real frame.


In the GIFEncoder version, it accepts a Bitmap. Well, that doesn’t exist in Javascript (natively, anyway) so instead, I use what I feel is a decent analogue: the canvas context. However, if you’re in a situation where you don’t have a real <canvas> element. That’s okay. You can set the second parameter to true and pass a array as your first argument. So in other words, you can do encoder.addFrame(fake_imageData, true) as an alternative. However, you must do an encoder.setSize(width, height); before you do any of the addFrames if you pass a array. If you pass a canvas context, then that’s all okay, because it will automagically do a setSize with the canvas width/height stuff.

Now the last part is to finalize the animation and get it for display.

  var binary_gif = //notice this is different from the as3gif package!
  var data_url = 'data:image/gif;base64,'+encode64(binary_gif);


Each of the files exposes a single global (see, at least it’s considerate!). But since there’s three files, that means that there’s three globals. But two of them are more of supporting libraries that I don’t totally understand or care about enough to document. So I’m just gonna document GIFEncoder.

new GIFEncoder() This is super parent function. You really don’t need the new keyword because It’s not really even using any special inheritance pattern. It’s a closure that does some var blah = exports.blah = function blah(){ for no good reason. Anyway, it returns an object with a bunch of methods that the section will be devoted to documenting. Note that I’ve never tested more than half of these, so good luck.

Boolean start() This writes the GIF Header and returns false if it fails.

Boolean addFrame(CanvasRenderingContext2D context) This is the magical magic behind everything. This adds a frame.

Boolean addFrame(CanvasPixelArray image, true) This is the magical magic behind everything. This adds a frame. This time you need you pass true as the second argument and then magic strikes and it loads your canvas pixel array (which can be a real array, I dont care and I think the program has learned from my constant apathy to also not care). But note that if you do, you must first manually call setSize which is happily defined just below this one.

void setSize(width, height) Sets the canvas size. It’s supposed to be private, but I’m exposing it anyway. Gets called automagically as the size of the first frame if you don’t do that crappy hacky hack.

void setDelay(int milliseconds) the number of milliseconds to wait on each frame

void setDispose(int code) Sets the GIF frame disposal code for the last added frame and any subsequent frames. Default is 0 if no transparent color has been set, otherwise 2. I have no clue what this means so I just copypasted it from the actionscript docs.

void setFrameRate(Number fps) Sets frame rate in frames per second. Equivalent to setDelay(1000/fps). I think that’s stupid.

void setQuality(int quality) Sets quality of color quantization (conversion of images to the maximum 256 colors allowed by the GIF specification). Lower values (minimum = 1) produce better colors, but slow processing significantly. 10 is the default, and produces good color mapping at reasonable speeds. Values greater than 20 do not yield significant improvements in speed. BLAH BLAH BLAH. Whatever

void setRepeat(int iter) Sets the number of times the set of GIF frames should be played. Default is 1; 0 means play indefinitely. Must be invoked before the first image is added.

void setTransparent(Number color) Sets the transparent color for the last added frame and any subsequent frames. Since all colors are subject to modification in the quantization process, the color in the final palette for each frame closest to the given color becomes the transparent color for that frame. May be set to null to indicate no transparent color.

ByteArray finish() Adds final trailer to the GIF stream, if you don’t call the finish method the GIF stream will not be valid.

String stream() Yay the only function that returns a non void/boolean. It’s the magical stream function which should have been a getter which JS does support but I didnt’ feel like making it a getter because getters are so weird and inconsistent. Like sure there’s the nice pretty get thing but I think IE9/8 doesn’t implement it because it’s non standard or something and replaced it with a hideously ugly blah blah. So Anyway, it’s a function. It returns a byteArray with three writeByte functions that you wouldn’t care about and a getData() function which returns a binary string with the GIF. There’s also a .bin attribute which contains an array with the binary stuff that I don’t care about.


The process isn’t really the fastest thing ever, so you should use WebWorkers for piecing together animations more than a few frames long.

I haven’t actually tried it yet, but here’s some incomplete mock-JS which should be able to do stuff once you add the boring stuff like serializing and deserializing the content (actually, i have most of the serializing done but you have to deserialize that and that’s really the boring part).

var frame_index,
    imageData; //get it from onmessage

var encoder = new GIFEncoder(); //create a new GIFEncoder for every new job
if(frame_index == 0){
  encoder.setProperties(true, true); //started, firstFrame
encoder.setSize(height, width);
encoder.addFrame(imageData, true);
if(frame_length == frame_index){
postMessage(frame_index + //on the page, search for the GIF89a to see the frame_index

var animation_parts = new Array(frame_length);
//on the handler side:

var worker = new WebWorker('blahblahblah.js');
worker.onmessage = function(e){
  //handle stuff, like get the frame_index
  animation_parts[frame_index] = frame_data;
  //check when everything else is done and then do animation_parts.join('') and have fun
var imdata = context.getImageData(0,0,canvas.width,canvas.height)
var len = canvas.width * canvas.height * 4;
var imarray = [];
for(var i = 0; i < len; i++){

worker.postMessage(frame_index + ';' + frame_length + ';' + canvas.height + ';' + canvas.width + ';' + imarray.join(','))

Ajax Animator + Wave 07 September 2009

sadly it led to this

So I think that the Ajax Animator Wave thingy is almost done. I think it’s really awesome, there’s some new stuff in there that may help in collaboration. There is still a bit of dogfooding left (VectorEditor needs to be updated as while the new version of Raphael is being used which eliminates a lot of the hacks being used, the change in path APIs means that lines, polylines and paths all fail). So after a bit of more bug testing, I think it’s going to be pretty cool. It will definately be out by the time the 100,000 people join Google Wave (I can’t wait!). But I’m not sure if it will be today, next week, or the week after that.

So to show some cool stuff I can do, I’ll publish the first time this blog has ever really seen an animation by me. But here’s the first animation I’ve made (It uses the Wave, center and flip plugins which you can access in the script executor, but someone could easily and tediously do this by hand too):

Try ignoring the probable trademark infringement.

The cool stuff being used here are first the ability to draw a rectangle, to multi-select, multi-copy, multi-paste and manual repeatition. After that, it’s multi-dragged down, and next frame then, the Ax.plugins\["center"]() plugin is called which obviously centers all of them (by the Y axis, preserving the X one). Then it goes to the next keyframe and using Ax.plugins["Sine"](100,0.01) (first arg defines multiplier for y axis and latter defines something I forgot, i think multiplier for the current X axis). Then the same function but with (100,0.02) and then Ax.plugins.flip() to make it look like the wave logo. Do some multi-select and set the color. After that cool stuff, it gets saved as text and opened in OnlyPaths Ajax Animator (which also demos a really cool feature called forwards-compatibility). It gets saved as a GIF and uploaded to my blog after that.

Standalone Animation Player 16 July 2008

I’ve created an animation player. It works with all ajax animator animations, and when compressed is a mere 3kb (which I believe is lower than OnlyPath Viewer).

It is built using the very same sources of the Ajax Animator, the whole purpose of all those *_core.js files. It uses the files Ext.ux.clone.js, op_view.js, svgrenderer_mini.js, vmlrenderer_mini.js, wrapper_core.js, view_wrapper.js, and tween_core.js.

svgrenderer_mini.js when compressed is just over 1.1kb and same is for vmlrenderer_mini.js

I’m on my linux development environment now, so I haven’t tested it in IE, but it will 100% fail, as the rendering engines is not detected and it uses SVGRenderer always.

See it in action here: