Andy Li’s Blog - Flex

Colorblink - An AIR app that simulates how color blind people see Flash and images

2010-02-19T20:55:00+08:00

Accessibility is a an important part of both web and game design. And for web and game design, one of the popular tool is Flash. That means very often you need to ensure accessibility in Flash. However there are still not many tools available even for simple things like color blind simulation… so I write my own:)

>> download installer (.air)

It’s a very simple AIR app. You open it, drop a swf file on its window, select the color blind type and that’s it.

The inner of Colorblink is using a Pixel Bender filter, applying to the whole application. The algorithm is just a color transform matrix, found in a Java Color-Blindness Simulators. That simulator have more simulation config, which I used only the simplest one.

This is also my first time using a git repo. So go to have a look, see if you can fork it for more features.

One thing is, there is problem loading Flex applications into Colorblink… I don’t know how to read the loaded app’s default width and height and then resize it… So, if you want to test your Flex app, get the filter and apply it to your app manually (can’t be easier).
Now you can load Flex swf or even html file! But the app wouldn’t resize automatically since the size cannot be determined. If Colorblink does not work for you, you can still always get the filter and apply it to your app manually (can’t be easier).

Oh, yes, there is a simulation of what a dog sees… So, design some game for your dogs in your free time…

Bicubic resampling by Pixel Bender

2009-08-25T07:51:00+08:00

There is bilinear resampling by Pixel Bender already, why not bicubic too?

With the very helpful Java implementation, I can get bicubic resampling running in Pixel Bender in hours.

Here is my result, along with the resampling results in PhotoShop as a comparison:

Source image (4x4), scaled by your browser):

Source image enlarged in PS (nearest neighbor):

Bicubic resampling by Pixel Bender:

There is some difference with PhotoShop’s versions (below), hope it’s not my mistake…

Bicubic resampling by PhotoShop:

Bicubic smoother by PhotoShop:

Bicubic sharper by PhotoShop:

My codes can be downloaded below:
Bicubic resampling sample program source (with PB source)

Update:
Notified by author of the Java version, the Java code was wrong and has been updated. Here below is my updated code:
Bicubic resampling sample program source (with PB source)

updated output of PB:

Update (2010-11-17):
Once again notified by Paul, the author of the Java version, there is something need to be updated. Here below is my updated code:
Bicubic resampling sample program source (with PB source)

updated output of PB:

Playing with chroma key and thresholding in Flash (with Pixel Bender)

2009-08-18T06:22:00+08:00

While traveling with my gf in Europe, I’m planning to develop a better technique to use color marker in FLARtoolkit (which I’ve tried before).

For the first step of doing so is to find a algorithm of matching colors. Using blend mode “difference” on the image is not flexible and may not fit all situations. I decided to calculate the difference by comparing hue, saturation and brightness of the colors and then threshold the image.

This is very similar to (if not exactly) doing chroma key. Maybe there is some awesome beautiful chroma key algorithm but I can’t find a fast and flexible enough to do so. If you know one, please tell me. :)

One problem I faced is choosing between color space models. RGB surely wouldn’t be the choice since it do not give hue value directly. There are HSV and HSL I found to be quite suitable. The two models share the same algorithm to calculate hue but have different ones for saturation and brightness. After reading the algorithms, my decision is… try both. :P

Another problem is how to preform thresholding. First method is after calculating the pixel difference, add the difference in hue, saturation and brightness altogether with weightings and do a one-time threshold to the grayscale image. Second method is calculate the difference and give threshold limits to the three channels (H,S,V or H,S,L), only the pixels pass all the three thresholds will be white. First method should be more easily to incorporate with other filters developed for AR (like the very hot adaptive thresholding), but the second method can be more precise. Finally I tried both too…

Here is the result. While I have set some default values to the filters, be sure to play around with the values when you change the target color. There wouldn’t be a set of values that fits all methods and situations. :)

I’ll try integrate it with FLARtoolkit and release the source when it is ready, be sure to check back soon. :)

Update:
Source and new demo is here!

Simulating atomic model of metal by Box2DFlash

2009-07-14T01:49:00+08:00

Impressed by the video here, I tried to simulate the atomic model of metal in Flash using Box2DFlash.

What is done in the program is just put a lot of spheres in the area randomly, and then let the physics engine to solve all the collisions. When all the atoms stop moving, a single still of the metal structure will be formed.

The atoms are only drawn on the screen when it is sleeping (i.e.. no movement). It can save some time from not rendering them in each frame.

caution: The browser will freeze for a few seconds after “start” is pressed. And it takes several minutes to an hour to finish (when sleep count == atom count).

source

PV3D + Async-threading = Async Render Engine

2009-06-07T03:28:00+08:00

Recently I need to write a 3D tool to help making a installation artwork. I know I should use Maya, Processing or anything like that, but in order to get the least risk, I used my most experienced language, AS3.

Since I need to render A LOT of stuff (\~400,000 objects), instantly I faced the performance issue. As you can imagine, even if I could generate all the objects in 15 seconds, the rendering process must excess the Flash Player’s execution time limit.

So I try to make my own async render engine with the help of async-threading. I extended BasicRenderEngine to AsyncBasicRenderEngine. The class even has a showBusyCursor property that let you optionally show the busy cursor on rendering.

But note that this is only a proof-of-concept and actually has little help of preventing freeze-screen. It is because I only distribute the individual 3D object’s rendering to frames but leaving the sorting, filtering, post-process code unchanged. Also, the RenderStatistics returned by renderScene/renderLayers will contain only wrong data until the RENDER_DONE event is dispatched.

One last thing, Flash’s drawing algorithm seems affecting the async rendering performance too. So I do not add the viewport to stage. Instead, once RENDER_DONE, I draw the viewport on a Bitmap on stage.

source

Vector Sound Wave Morphing

2009-05-20T06:53:00+08:00

This my my final project for the course “Interactivity I”. For this final project, my aim is to explore the vector nature of sound wave while making a tool to let people create their own waveform which can then be saved for other use.

The waveform in the program consists of 10 control points. The first point and the last point are fixed at zero so that the wave can be looped smoothly to form a sound wave. The controls points can be adjusted by dragging or by using keyboard. The points are assigned with keys labelled near them, which are number keys (+shift to move points up instead of down). I recommend using the keyboard as you may adjust multiple points at the same time (which feels like using multitouch surface 8-) ).

Degrafa is used to construct the wave form. I choose to use cubic bezier curve as it is easier for me to implement the algorithm (with the still-in-beta AdvancedCubicBezier which available via SVN).

The 3D cylinder is made by Flash Player 10’s 3D API. It looks quite nice as similar to landscapes.

Sound is synthesized dynamically in real-time (with some delay… okay? ;-) ). If you hear some “clicks” or “pops”, try to export the sound first by clicking on the export button at the bottom-right corner (it will be in wav format, encoded by the WavEncoder from popforge) .

If you hear nothing, you may try to increase the buffer size or use the export function.

source

Data structure assignment - Coin Collecting Game

2008-11-03T04:56:00+08:00

It is just a simple game (If it is really a game), but I was having fun with Flex and PaperVision3D.