somewhere to talk about random ideas and projects like everyone else


stick2 a simple skeleton based stop-motion stick figure animator



JavaScript <canvas> to (Animated) GIF 23 July 2010

This is the GIF which was generated from the canvas.

This is the raw canvas element saved as a non-animated PNG

I’ve tried this before but it didn’t work. <canvas> can’t do toDataURL('image/gif'), and the primitive GLIF library couldn’t do much so I never had the opportunity to test my gif-merging code that I had. But I’m at it again, this time, porting it from the AS3GIF library, an awesomely comprehensive bitmap to binary gif encoder that even supports LZW compression (and the patent has luckily expired. Yay!). AS3Gif is supposed to “play and encode animated GIFs”, but since web pages can usually natively play GIFs fine, it’s only a port of the GIFEncoder portions of the library. And it works really well. The rest of this post is copied from the Github readme. Interesting how the w2_embed/anonybot embed post was a blog post turned into readme, this is a readme turned into blogpost. I’ll start with a link to the Github repo anyway:

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.!

This is the GIF which was generated from the canvas.

You first need to include the JS files. It’s probably best if you include it in this order, but it shouldnt’ 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 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. encoder.addFrame(context);

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. You can find the rest of the WebWorkers section on the actual readme, because the rest is just a huge block of code with comments.

stick figure animator 22 June 2010

One thing the ajax animator’s pretty bad at is stick figures. Sure it’s not impossible, but it can’t really compare with the ol-fashioned frame-by-frame joint-manipulation likeness of Pivot. It’s called stick2 because the original experiment with stickfigures was named stick.html, and when I went to extend it and didn’t feel like setting up a git/svn repo, I copied the file and named it stick2.html, and with no good project-naming skills, it stayed that way.

Anyway, this was a project that got pretty close to completion in early march, but I never bothered to blog about it until now. It should work pretty not-bad on an iPad J(except the color picker), though honestly, I’ve never tried it.

The interface is pure jQuery/html/css. The graphics are done with Raphael, but the player actually uses <canvas> for no particular reason.

Basically, it’s organized into two panels, the left-side figures-box and the bottom timeline. The figures-box contains figures (amazing!) and clicking on them adds them to your canvas. The two defaults are the pivot-style stickman, and something called “blank” which is a root node with no additional nodes. Though it shows up as a orange dot, unless you add something to it, it doesn’t have any actual look when viewed in the player.

On top is the context-sensitive buttons. Well the buttons in my screenshot aren’t context sensitive, they’re permanent. But when you click on a node, a new set of buttons (and words too!) appears. One is a line and the other is a circle. Click them to add a new segment or circle to the currently selected node. Then are various settings for the current segment (each node other than the root one is associated with a segment). Clicking those allows you to modify them. Also, a red X appears on the right, and that basically means remove the node and the child nodes.

So, now you have some extra nodes, how do you change them? Simply hold it down and drag, and the the segments move as well. But note that the length of the segment doesn’t change as you move it. That’s because by default, it locks the length of the segments. There are two ways to get around it. The first is to hold shift while dragging. The second is to tap the little lock icon on the top left.

On the bottom, is the timeline with live-previews of your frames with a semitransparent gray backdrop of numbers. Switch between each one by clicking on them and add one at the end by hitting the green “Add new frame” button.

On the canvas, there are two yellow squares, those allow you to resize the canvas.

On the very left of the top toolbar, is the play button. Hit it and the figures toolbox minimizes and it plays out your animation. Click it again to get back. Then is a little upload button. Hit it and then a little box pops up with a link to where you can find your animation in a way that you can share and to edit (not actually edit, but more like fork, as each save is given a unique id). Next is the download button which you hit, and get prompted by a big prompt-box which you use to paste in the ID of the animation you (or someone else) has saved, so you can edit it. Most of the time that’s useless as when you send a link with the player, it has a button which says “Edit”.

Sample animation:

Try the application out:


Stick Figures! 27 February 2010

Ubuntu’s weird and adding a bar on top of all my screenshots

I like stick figures, and browsing YouTube, I found some things on Pivot and Pencil (really awesome free desktop animation apps), and that made me think, Stick figures are awesome. So I’m going to add some better Stick Figure features into Ajax Animator and possibly upstream to VectorEditor eventually.