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Zwibbler: A simple drawing program using Javascript and Canvas
Posted on: 2009-12-28 16:17:47

Tested under Firefox 3.5.6 and Google Chrome


This project extends the technique I created for imprecise line-drawing to create an entire vector graphics application, similar to Inkscape. It is written almost entirely in Javascript, except for a server-side program that renders text.

See below if you are interested in the implementation and coding parts.


  • Download and share your drawings in PNG, PDF, or SVG formats.
  • Box, circle, lines, and curve primitive shapes
  • Shadows when supported by browser
  • Text in several hand-drawn fonts rendered on the server
  • Rotate & scale shapes individually or in groups
  • Select colours using an HSV colour wheel.
  • Unlimited levels of Undo/Redo


Users who are familiar with vector graphics programs such as CorelDRAW! or Inkscape will have no problem using it, because the some of the most common keyboard shortcuts work the same way. Otherwise, it will take some getting used to.

List of keyboard shortcuts

The keyboard is the only way to do some things.

CStart drawing a new curve
LStart drawing a new line
Ctrl+DDuplicate selection
Page UpMove selected shapes toward you
Page DownMove selected shapes away from you
HomeBring selected shapes to front
EndSend selecting shapes to back
Ctrl+GGroup selected shapes
Ctrl+Shift+GUn-group selected shapes
+Zoom in
-Zoom out
Shift +Restore normal zooming
Arrow KeysMove around while zoomed-in

Saving and loading

Drawings can be stored on the website by clicking on "Save". If you do not have an account, the drawings will be deleted in a few hours, or if you close your web browser. As soon as you create an account, the drawings will be transferred to long term storage.

If you don't want to create an account, the "Save" option will also allow you to download your drawing as an image.

Drawing simple shapes

Click on the rectangle or circle tool in the toolbar, and the desired shapes will immediately appear in the upper left of the drawing area. You can then drag them to where you want to go.

No two shapes are alike. If you create two circles, they will be slightly different. However, if you duplicate a shape using Ctrl+D, the duplicate will be exactly the same.

Drawing lines and curves

To draw a line, click the line tool in the toolbar, then click anywhere in the drawing window to place the first point. You can then click again to place the second point, and so on. To end the line, double click. If you end the line or curve close enough to where you started it, then it will create a closed shape.

Hint: The line tool can be activated by pressing "L", and the curve tool can be activated by pressing "C".

Lines have a sloppiness property that can be set after drawing it. To set the property, select on the line you have drawn. The options pertaining to the line will appear to the left of the drawing window.

Curves do not have sloppiness, but smoothness. By increasing smoothness, the curve is modified to make rounder corners.

Drawing text

Text is placed the same way as circles or rectangles. Click on the text tool, and some default text is placed in the upper left of the image. You can change what the text says by clicking on the text, and then modifying the "text" property that appears to the right of the canvas.

Example: Editing text using the properties area

You can move, scale, or rotate text. However, in this version of the drawing software, scaling will result in loss of quality. Instead, change the font size in the properties area.

Selecting things

While not in line or curve mode, you can select things by dragging a box around them using the mouse. The box must fully enclose the shapes to select them. You can also add a shape to an existing selection by pressing the shift key while clicking it.

Overlapping shapes

You can move a shape to the front using the Home key on the keyboard. Send it to the back using the End key.

Point edit mode

For some shapes, you can move the corners around by entering "Edit" mode. You can enter edit move by clicking on an already-selected object. In edit mode, the corners that you can move are highlighted using a blue box.

Example: Point edit mode


Delete all objects in the selection by hitting the Delete key on the keyboard.


To avoid having to repeatedly select complex groups of shapes, you can "group" the current selection using Ctrl+G. Now, when you click on any one of the group members, all will be selected. You can break apart any selected groups using Ctrl+Shift+G.


You can copy pieces of your drawings between documents and browser windows. While there are shapes selected, click on "Copy" and they will be transferred to the zwibbler clipboard, stored in your browser. You can then open another document later or in another browser window and paste the shapes there.


While there are shapes selected, you can duplicate them by pressing Ctrl+D. Copies of the objects will appear over the existing ones. You will have to move them aside to see the effect.

Zooming in

Increase magnification by pressing +. Decrease by pressing -. Restore to original magnification by pressing Shift+'+'. While zoomed in, you can move around using the arrow keys on the keyboard.


The last 10% of work to make a polished program takes 90% of the time. I know about these bugs:
  • Scaling text reduces its quality.
  • There's no way to set the background colour of a drawing.

Implementation Notes

I should write something about the implementation. Hmm, the undo stack is pretty standard stuff but may be new to some people. But the thing I was happiest to find was the concept of abstracted Mouse Behaviours.

Design patterns for mouse behaviour are slim pickings. When a novice programmer designs a mouse-intensive application, he or she will tend to make a very complex function that deals with all possible cases when the mouse is clicked or moved. It can quickly grow to be unmaintainable.

To deal with this complexity, we separate the possible states of the system into various MouseBehaviour objects, which implement onMouseDown(x,y), onMouseUp(x,y), and onMouseMove(x,y). (This is a variation on the State design pattern). The default mouse behaviour is the selection mode. If you press the mouse button while over something, it then replaces the default mouse behaviour with a new mouse behaviour. When you lift the button, the new behaviour ends and reverts back to the previous behaviour. This keeps everything simple. There are several mouse behaviours:

  1. DefaultBehaviour -- Depending on where you click, it replaces the current behaviour with a new instance of one of the other behaviours.
  2. SelectBoxBehaviour -- if you click on an empty area of the image, it handles drawing the select box. When you lift the button, it selects everything in the rectangle you have drawn.
  3. TransformSelection -- if you clicked on a selection handle, then it transforms the selected shapes as you move the mouse.
  4. MoveEditNodeBehaviour -- If you click a blue edit node, then it moves the node.
  5. DrawLinesBehaviour -- Places points in a line shape until you double-click to end it.
These objects can be found in DrawView.js


Zwibbler.com is not open source. All source code is Copyright 2010 Hanov Solutions Inc. Drawings produced by you using zwibbler.com remain your property.

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Sylvain Caillet

2009-12-29 11:45:48
It sounds very interesting. But I need some time to study the javascript mechanics :-)


2009-12-29 12:47:30
Love the sloppyness factor, but rather surprised that a sloppy filled area is "perfectly" filled - surely the color should not quite reach the border in some places, and bleed outside it in others?


2009-12-29 13:19:56
wow. very cool... The beauty of it is its rawness and imperfect look... i love it. going to play with it some more.

Ben Jones

2009-12-29 20:03:35
Can't seem to stop drawing a lines. Any leads? (using Firefox 3.5.6)

Ben Jones

2009-12-29 20:04:05
Sweet job by the way.

Tom Leys

2009-12-29 21:08:55
To stop drawing a line, double click where you want it to end.

Very cute little webapp.

Ben Jones

2009-12-29 22:01:17
Double Click...it works.


2009-12-29 23:36:11
Could you put a license on this, MIT maybe? I think I could use this on an upcoming project.


2009-12-30 09:38:04
Tested on Opera 10, too. Looks like it's fully working :)

David Robbins

2009-12-30 11:00:16
Great tool. Is there a way to generate the image as a png or jpeg? This would be awesome.

David Robbins

2009-12-31 10:30:00
Sorry I didn't read your post more closely - the image saving feature works in FireFox, but not in Chrome, so you can disregard my last comment. Any thoughts as to why Chrome will not work?

I've just discovered your blog and am really enjoying it.

dave t

2010-01-04 15:10:49
this is awesome, thanks for sharing. have you considered open sourcing this?

Stefan Siebel

2010-01-05 15:50:04
Great stuff! Thanks for sharing!

Alice (aka Steve\'s wife)

2010-01-18 22:37:06
Hahahaha! That comic is so you it's ridiculous!

Dana Moore, BBN Technologies

2010-01-20 17:46:28
Totally love the functionality!

Nicely implemented.

Really fun to us. The big wow factor for me is that simple cartoons often get the point across better than powerpoints or Omnigraphs which take far more time and energy to produce.

Really marvelous work. If you decide to open source, I would love to help take to the next step (not that it needs to be improved really -- as it stands it's really quite marvelous!); but a couple thoughts I have:

* object linking with a semantic KB?

* overlay planes over a visual backdrop (e.g., photo, screencap)?

* templates?

* Domain specific object palettes?

* layers?

* audio annotation?


Sean Doughtie

2010-02-02 22:51:01
Good Work!

I looked at the source and there is not license info... are you planning to release under a standard license?

Tom Bortels

2010-02-08 00:28:54
This is seriously awesome, Steve. Thank you for sharing.

I'd like to see point editing for curves - I'd be in hog heaven if I could mess with the Bezier curve handles.

I too am interested in license - I'd dearly love to copy this out and hack it into... well, frankly, something that draws spaceships. Some preset objects, a symmetry mode; it's be sweet. Fingers crossed for MIT or such...

Scott Francis

2010-02-08 19:31:16
+1 for a BSD licensed version (I'm frankly surprised Google Docs hasn't released something like this already; VIsio is pretty much the only non-gaming reason I keep Windows around anymore, and I'd dearly love a web-based version!)


2010-02-09 14:27:20
Really nice little app - thanks!


2010-02-12 04:39:34

2 RFEs: line arrows, and OpenID sing-in

Thanks for this tool


2010-02-20 17:47:34
Love it!

This makes sketching so much nicer, because it's equally accurate than my drawing, but just looks better.

Wish there was a "real" app like this for everyday offline use.


2010-03-05 06:42:24
Hi, very nice work

You can implement the saving in png option with the function .toUrl(), then ajax the previous content generated to a PHP script with png header in ;)


2010-03-27 07:47:13
Hello. I tried to run on my computer but the text did not appear. this may cause.

Steve Hanov

2010-04-05 22:25:52
Although the source code is available the software is not open source. I may use this commercially in the future. (Or you can if you send enough money.)

However rest assured that I am taking all reasonable precautions to keep your saved data available.


2010-04-09 17:31:11
have you made any thoughts towards licensing costs, or freehand drawing?

Thiago Mata

2010-04-17 07:58:55
Man, you should make a post into your blog just about this image rotation using matrix operations. I try to understand just reading your code but it not that easy ( still trying );

Very good work. Very nice tool.

Sean Doughtie

2010-04-23 00:46:29
>(Or you can if you send enough money.)

how much are we talking about?

Matthew Wilson

2010-05-02 12:48:51
I don't seem to be able to change the text value in FF 3.6.4.


2010-05-04 07:46:04
Very interesting application. I have a question. Would it be possible to save on the server the final draw in gif, with the background as transparent? Don't know if I am asking too much

Sean Doughtie

2010-05-10 16:22:50
>Would it be possible to save on the server the final draw in gif, with the background as transparent?

or perhaps download an SVG


2010-06-02 09:08:40
But how can I save it to add to my sharepoint sites?

Toby Bennett

2010-06-17 04:59:53
Cool. The text nearly works but it doesn't update what I type in (I'm using Opera)

Steve Hanov

2010-06-17 09:00:40

You have to press Enter when you finish typing to update the text. But now that you mention it I can see how it is a problem. Thanks for pointing it out.

Harry Roberts

2010-06-19 19:58:56
This is great, if you give it the ability to draw over websites ala twiddla.com we would pay for this. I don't care about chat, gchat if fine for that.

David Spector

2010-07-29 19:30:39
Wow, I am really impressed. Your code is beautiful, and the app seems bulletproof--quite an achievement for JavaScript. It's a hot app for any business. I wish you success!

Springtime Software

Scott Richards

2010-08-05 13:55:05
This is beautiful. Did you write the color picker yourself? I would like to get my hands on that code... Keep up the good work!


2010-09-28 02:50:26
How to do "carriage return" in text ?

Thank you

Steve Hanov

2010-09-28 07:32:13
There is no ability to do multiline text. I admit that text handling is not easy.

Jerry Myroup

2010-10-01 09:49:20
Hi Steve

I created a windows application that behaves in a similar fashion to your application. If you do a search on youtube for procadtivity, you will find 3 or 4 videos showing my application in use. I would be very interested in working with you to create a drawing application that would be faster than anything on the market today. Email:gmyroup@digitalfreehand.com

D. Sohin

2010-10-05 21:00:11

why don't you put your invention on github,

so everybody could collaborate on this awesome project

and have like an ass-load of benefits from it?

N Mitra

2010-12-30 15:01:46
Nice application. For zoom in "ctrl+" is working. DrawView.js link is broken. Kindly update. Want to know what exactly is abstracted mouse behavior.


2011-02-17 14:28:27
It would be cool if you could send an invite to allow other users to join your drawing as observers, or pass control to them to allow them to add to your drawing.


2011-03-21 03:43:31
i really would like to see an open source project like this


2011-04-11 08:44:43
Used this three times.

First time: saved, closed, tried to reopen - TypeError: a is null

Second time - Blue Screen of Death

Third time - Saved, tried to get pdf, got: TypeError: a is null

Firefox 3.6


2011-06-01 02:50:55
neat app! you should make it multiuser! : )

here's a tutorial on multiuser sketch pads to get you started...




2011-06-19 18:21:38

How can we display the properties panel in the embedded version of zwibber ?

Thank you.


2011-07-07 10:56:10
How do I reset my password?


2011-08-23 12:13:42
where the name come from? Zwibbler? Is that german?


2011-09-11 12:08:45
How can i apply this to my webpage?

Thank you guys


2011-11-01 13:22:26
hello , i was looking for a web page online tht allow me to create a brain storming scheme and the most similar thing tht i have found is ur system .

my compliment, maybe you can implement the program in this way , because i have not found the page tht i was looking for.


good and usefull work

Gary P

2012-06-02 10:52:18
kind of an old post but I'm interested in using this (adding in pasting of clipart we have).. Would love to license it.. Any options? still "closed source"? What does "send enough money mean?"



2013-02-28 20:03:14
can i have the coding in java for this. for studying purposes only. plss :(

znorfiq@gmail.com..pls email me as soon as possible

tevel Software

2013-03-20 09:19:46
Hallo all

We are looking for a simple server side drawing software to add to our web site.

The reason we need it is that we want to have the ability to actually "sign" customers on a web form (using their finger/stylus) using a tablet/smartphone.

We need a simple software with an API that allows the signing/drawing in b/w (no need for colors, brushes, etc...), and saving the image created as a file in our server. The file needs to be saved in a JPG/BMP format.

Do you have something a simple as that ?

Best Regards

Asaf Willensky

Tevel Software



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