The webapp version adds:

• offline mode via HTML5 cache
• full-screen mode
• two-finger pan/zoom (upto 4x)

To use the full-screen & offline mode on your iPhone/iPod Touch(/iPad?), bookmark the page and select “Add to Home Screen”.

Desktop browser enhancements

Other added features for desktop browsers include:

• autosave feature
• session save
• undo (de facto!)

Alas, the autosave feature doesn’t work on the iPhone OS 3.1.3 due to the canvas origin-flag bug (hopefully this’ll be fixed on OS 3.2!).  It works nicely on FF 3.6, Chrome 4.x, and Safari 4.x.  After a brief delay after the last user stroke (about 5 secs), the state of the canvas and the last brush is saved to sessionStorage (or localStorage in the case of Chrome as it doesn’t fully support sessionStorage yet).

This provides a convenient undo feature as well.  Don’t like your last few stroke, F5 (refresh) and zap! (You’ve got 5 seconds to decide!)

If localStorage is available (as in the three browsers mentioned) and ‘save‘ button is clicked, the canvas is also saved to local storage.  So even if the browser is restarted, it’ll start at the last saved canvas.

Thanks to Ricardo Cabello for this great tool.

Try it: Harmony webapp.

Note: As Ricardo mentions in the comments to his post, you can take a snapshot of the canvas on the iPhone/iPod touch by pressing the power button and home button at the same time.   This is probably the best way to save/share on the iPhone.

Update 1: 11 March 2010 — fixed offline issue.  Please re-install on iPhone/iPod Touch.

Update 2: Examples of the awesome sketches being created in Harmony:

- Polish artists: http://blip.pl/tags/harmony
- alternatyves: here, here, and here
- in color
- more

Lastly, there’s the question of how concerned Apple is, strategically, that a robust web app API and market would take away from the App Store. And if so, are they worried about the money? I’d guess probably not. I don’t think Apple’s 30 percent cut of App Store revenue is anything to sneeze at, and it’s growing fast. But there’s no question that the App Store exists to sell iPhones and iPod Touches, not the other way around.

via ★ More on PastryKit.

via Chrome Extensions and webOS Applications look quite similar.