I doubt you ll get anything higher resolution than the "onmousemove" event gives you, without writing an efficient assembler program on some embedded system custom built for the purpose. You run inside an OS, you play by the OS s rules, which means you re limited by the frequency of the timeslices an OS will give you. (usually about 100 per second, fluxuating depending on load) I ve not used a tablet that can overcome the "polygon" problem, and I ve used some high end tablets. Photoshop overcomes the problem with cubic interpolation.

That is, unless, you have a very special tablet that will capture many movement events and queue them up to some internal buffer, and send a whole packet of coordinates at a time when it dispatches data to the OS. I ve looked at tablet api s though, and they only give one set of coordinates at a time, so if this is going to happen, you ll need custom hardware, and a custom driver, and custom apis that can handle packets of multiple coordinates.

Or you could just use a damned canvas tag, the onmousemove event, event.pageX|pageY some cubic interpolation, the "toDataURI" api of canvas, post the result to your php script, and then just say you did all that other fancy stuff.

onmousemove, in my tests, will give you one event per pixel of movement, limited only by the speed of the event loop in the browser. You ll get sparse data points (polygons) with fast movement and that s as good as it gets without a huge research grant and a hardware designer. Deal.

there are some applets for this in the oekaki world: Shi painter, Chibipaint or PaintBBS. Here you have php classes for integration.

Drawings produced by these applets can have quite good quality. If you register in oekakicentral.com you can see all the galleries and some drawings have an animation link that shows how was it drawn (it depends on the applet), so you can compare the possibilities of the applets. Some of them are open source.

Edit: See also this made in HTML 5.

Have a look at <InputDraw/>: a flash component that turns freehand drawing into SVG. Then you could send back the generated SVG to your server.

It s free for non commercial use. According to their site, commercial use price is 29€. It s not open source though.

IMHO it s worth a look.

Alternatively, you implement something based on svg-edit which is open source and uses jQuery (demo). If requires the Google Frame Plugin for IE6+ support though.

EDIT: I just found the svg-freehand-signature project (demo) that captures your handwritten signature and sends it to a server as a SVG using POST. It s distributed as a straight-forward and self-contained zip (works out of the box with Safari and Firefox, you may want to combine it with svgweb that brings SVG support to Internet Explorer).

EDIT: I successfully combined Cesar Oliveira s canvaslol (just look at the source of the page to see how it works) with ExplorerCanvas to have something on IE. You can also have a look at Anne van Kesteren s Paintr experiment.

markup.io is doing that with an algorithm applied after the mouseup.

I asked a similar question recently, and got interesting but not satisfying answers: Is there any way to accelerate the mousemove event?