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Rendering Animated GIFs on the Canvas Element

This is probably as old as the very first implementations of the Canvas Element. But the truth is that I never thought about what could happen if you render an animated GIF in a Canvas through the drawImage method.

The results were somehow the ones I was expecting but the question is: could these be useful at any specific situation? My honest answer is, I don't really know yet.

I'm back, so is Monkey Island!

• Official Site
• Ron Gilbert comments

Benchmark on the Floor

In the projects I have been working lately I've had to test the speed of a bunch of JavaScript functions. That was another good excuse for me to read more about different ways of creating benchmarks that I didn't know of.

There's one test I want to mention here as it uses those obscure JavaScript syntax tricks that I like so much.

The goal of this test was to find a faster way to run the Math.floor function to see if we could make some heavy loops of our scripts even faster. Here is where the bitwise operators come into the game. I saw the "~~" trick in a forum thread and I found another two playing for a while with the JavaScript console (all of them round a number the same way). The average of all the A-Grade browsers tests gives us the following results:

• Math.floor(n): 15.804
• ~~n: 8.784
• n|n: 8.081
• n&n: 12.019

(Average time per instruction in microseconds)

Apparently, the n|n option will be the best candidate for our purpose. You can test it yourself in your browser:

Car Navigation Map in Canvas

After browsing through the code of Jacob Seidelin's Super Mario Kart demo, I was inspired to take the code and attempt to create a GPS-navigation system experience using publicly available roadmap tiles. The final result is a proof of concept that works pretty damn well in Firefox (and not quite that well in other browsers :).

After passing it around to a few friends, I've already heard some cool suggestions for taking the demo to the next level. So, please, if this inspires you, feel free to experiment further with the code. Enjoy!

JS Puzzle

Write a function getMax(a,b) that takes two integers and returns the maximum value. None of the following are allowed: >, <, ==, !=, Math.max, Math.min.

function getMax(a, b) {
 ...
 return max;
}

Send your answers here. I will post the solution in a few days.

Solution

Chromeflow

Based on the Rafi Adnan's coverflow+canvas sample posted in Ajaxian, I created a bookmarklet which will add more fun to the Most visited preview of your home page.

Simply drag the link below to your bookmarks bar in Chrome, open up a new tab (with the default home page), and click the bookmarklet to see your history displayed iTunes-style.

Chromeflow

(Press CTRL+B to make the bookmarks toolbar show up)

Drag and Drop without Drag and Drop

While experimenting the other day, I found out about a special behavior of input fields in web browsers. Mixing it up with images and the previous canvas experiment, I came up with a proof of concept that emulates image drag and drop behavior.

As a bonus, it also allows drag and drop between documents.

Demo

Update: Testing the demo in Google Chrome shows a funny highlighting effect when dragging images. Also, they can be dropped only in a small area on the top left of the text area.

Moving Forward

I think it's worth taking a look where canvas is positioned in the following graph shown by Vic Gundotra at the last Google IO (2008) when talking about the evolution of the web browser and how to "Move the web platform forward":

SXSW 2009

The canvas element has been generating increasingly more interest and broad web acceptance in the past year - noticeably more than similar technologies like SVG or VML that have been around for much longer.

Martin Kliehm has kindly offered me the opportunity to participate in a dual presentation at the next SXSW to talk about canvas and demonstrate some interesting uses.

If you are interested in the canvas element, you can cast your vote for this presentation (until August 29). And while you're at it, you might also want to cast your vote for canvas support in IE8.

Rendering Polygons with Canvas

This time I wanted to test the performance of the canvas rendering versus other technologies. Since Google Maps uses VML, SVG and image retrieval depending on which browser you are using, I compared the rendering times of the maps polygons to see the results.

In the end it wasn't the best environment to do the tests since it was impossible for me to split the actual rendering time of the polygons and the rest of the processes of the map code. In any case, I leave the experiment for you to see.

Canvas

I am releasing an experiment I made last October when I started playing with the canvas element.

One of the main reasons I started to play with this technology was that while I was trying to port a previous SVG experiment, I noticed it had quite a few cross browser issues. The final result with canvas was quite satisfactory and it gave me the chance to learn features beyond the basics such as drag and drop, event handlers and performance optimization.

Since that experiment in October my interests and prototypes in Canvas have been more and more challenging: Skewing techniques, VR emulation, polygon rendering, etc. There's a bunch of code to release though I am not allowed to release all of it right now. But I will do my best.

Update: Due to the interest and enhancement requests from friends and colleagues, I have created a project page where you can contribute and add items to the to do list.

Update 2: Check the Flickr and Picasa integration from Michael Johnston and Pamela Fox respectively.

JS Interpreter and Execution

Here is a quick (and tricky) mini challenge for those who usually work with javascript. Take a couple of minutes to think about the results of the alerts in each snippet.

// Snippet 1
x = 4;
function init() {
 alert(x);
 var x = x;
 alert(x);
}
init();
	

// Snippet 2
x = 4;
function init() {
 alert(x);
 // var x = x;
 alert(x);
}
init();
	

Walking the DOM

As an experiment I had the idea of implementing the iterative version of the walk the DOM recursive function (which uses firstChild and nextSibling DOM methods to walk the DOM tree as a binary tree). One of the conditions was I didn't want to use a stack in the iterative implementation. At some point, I had the hope that it could be faster than the recursive one due to the absence of the function-call overhead but that didn't happen.

With that said I will leave the code here for anyone who wants to spend more time playing with it or provide some feedback.

World Map Projections

As a big fan of world maps and also because I have been for a while programing some things on it, I am going to show my favorite world map projections:

This projection belongs to the equal-area projection category, which means it tries to represent countries in their correct proportional size. I think the first well known app using it was 43places.com.

For a long time, this map made in flash was the main map of the 43places application so the users were able to select countries and see which ones were visited, 'want to visit', etc. From my point of view this map was the best choice. However, they later switched to google maps maybe because of the specificity of the markers. Although you still can access the flash version from its users' profile.

This one belongs (among other categories) to the compromised projection ones. Its goal is to find a balance between different kinds of distortions.

That representation can be seen everywhere in the Wikipedia.

Probably the most popular of the Cyllindrical Equal-Area. However, similar projections like Behrmann or Hobo-Dyer make the countries look less strange. They all differ in the ratio of the vertical to horizontal axis, especially close to the pole areas

I haven't found any web app using them though.

Also called 'evil mercator' since it's the worst one in terms of distortion of the countries. Greenland is 554% bigger than its real size, Canada 258%, USA 68%, etc.

It's still commonly used in a lot of places. For instance, google maps uses it. Although my guess is that 95% of the use of google maps is not at the world view zoom level.

Acknowledgments

I have never been in the acknowledgments of a book before.

Ross Harmes from Yahoo! and Dustin Diaz from Google decided about a year ago to write a book about Javascript Design Patterns. As I have the honor of being on the team of the former, I was pleased to offer my feedback on his excellent lessons. Although one wonders who needs technical feedback when the beast Simon Willison is already doing that.

Javascript, being the first mainstream lambda language, has its very own features. It well deserves a good training not only to write better code but to use all the potential of the language. This book will really help you in both aspects and it will make your path easier to the mastery of the language.

If I feel happy to be mentioned in the book, I can't imagine how proud Ross and Dustin must feel to be the authors after months of work. In fact, it's a feeling that is worth a try.

Congratulations guys!

DevHouse

A nice picture from the second DevHouse I've been. This one happened last Saturday.

A-Grade Browsers

This is what happens when you mix the four A-Grade browsers.

Yahooed!

Image Transformations in Canvas with Slicing (by Ross Harmes and Ernest Delgado)

Published on the Yahoo! User Interface Blog

User registration patterns (URP)

In this article we will try to prove that some practices in current web apps have important privacy and security issues both for the user and for the application.

Read more...