Lanczos Resampling With ActionScript

It has been a while since I worked on some interesting library. But the day has come 🙂 and here it is. Let me introduce you LanczosBitmapDataResizer class. Lanczos resampling is an interpolation method used to compute new values for sampled data. In resampling (resizing) images it is considered to be one of the best algorithms at all. Lanczos is a convolution filters. That means a filter that for each output value moves the convolution functions point of origin to be centered on the output and then multiplies all the values in the input with the value of the convolution function (kernel) at that location and adds them together.

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Quick tip: embedding in Flex

In Flex application, you can embed your assets into 3 places: ActionScript, MXML, CSS. To embed into ActionScript use following syntax:

public var imageClass:Class;

[Embed(source="assets/library.swf", symbol="symbol1")]
public var symbol1Class:Class;

// flash library symbol alternative
public var symbol2Class:Class;

To embed into MXML use:

<mx:Image source="@Embed('assets/image.png')"/>
<mx:Image source="@Embed('assets/library.swf', symbol='symbol1')"/>
<mx:Image source="@Embed('assets/library.swf#symbol2')"/>
<mx:Button skin="{null}"/>

To embed asset into CSS file use syntax:

    upSkin: Embed(source="assets/image.png");
    overSkin: Embed(source="assets/library.swf", symbol="symbol1");
    downSkin: Embed(source="assets/library.swf#symbol2");

    font-family: Copacetix;
    src: url("assets/copacetix.ttf");
        U+0020-U+0040, /* Punctuation, Numbers */
        U+0041-U+005A, /* Upper-Case A-Z */
        U+005B-U+0060, /* Punctuation and Symbols */
        U+0061-U+007A, /* Lower-Case a-z */
        U+007B-U+007E; /* Punctuation and Symbols */

Embedding font to .as (.mxml):

[Embed(source="../arial.ttf", fontFamily="myArial")] 
public static const FONT_ARIAL:Class;
public static const FONT_ARIAL_NAME:String = "myArial";

[Embed(source="../fonts.swf", fontName="myCourier", fontWeight="bold|normal") ]
public static const FONT_COURIER:Class;

public function Test()
    var format:TextFormat = new TextFormat();
    format.font	= FONT_ARIAL_NAME;
    var tf:TextField = new TextField();
    tf.embedFonts = true;
    tf.defaultTextFormat = format;

Read more about embedding assets into ActionScript best practices here. Read basics about embedding here.

Bitmap, BitmapData, ByteArray…


Lets see how to convert between Bitmap, BitmapData and ByteArray in few examples:

  • DisplayObject to BitmapData
  • BitmapData to Bitmap
  • BitmapData to ByteArray
  • URL (image) to ByteArray (asynchronous)
  • URL (image) to BitmapData (asynchronous)
  • ByteArray to BitmapData (asynchronous)

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ActionScript 3 encoding JPEG, alchemy

Lets assume you want to save an image (or any DisplayObject) from flash to disk, or upload to facebook etc. What you need is to encode your BitmapData into an Jpeg and send ByteArray raw data to be saved/uploaded. There are few ways how to do it.

First, you can use original adobe Sadly, this encoder is the slowest. There were attemps to make it faster by otpimizing code by, that resulted into two times faster org.bytearray.images.JPEGEncoder. Usage is pretty simple:

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