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TITLE:Flash SWF 仕様

- 仕様書
--  http://www.adobe.com/devnet/swf/
---   flash_fileformat_specification.pdf

----

以下、(自分に)必要な文章だけ抜粋して意訳。

#contents

* Instoduction [#intro]

- SWF ファイルフォーマットはインターネット上でベクター画像/ビデオ/音声を運ぶもの。
- 運ぶものであって、画像エディターで画像をやり取りするものではない。
- 以下の目標をもってデザインされている
- On-screen display
--  The format is primarily intended for on-screen display and supports anti-aliasing, fast rendering to a bitmap of any color format, animation, and interactive buttons.
- Extensibility
- Extensibility (拡張性)
--  The format is a tagged format, so it can be evolved with new features while maintaining backward compatibility with earlier versions of Flash Player.
- Network delivery
--  The format can travel over a network with limited and unpredictable bandwidth.
--  The files are compressed to be small and support incremental rendering through streaming.
--  The SWF file format is a binary format and is not human readable like HTML.
--  The SWF file format uses techniques such as bit-packing and structures with optional fields to minimize file size.
- Simplicity
- Simplicity (簡易性)
--  The format is simple so that Flash Player is small and easily ported.
--  Also, Flash Player depends upon a limited set of operating system features only.
- File independence
--  The files display with minimal dependence on external resources such as fonts.
- スケーラビリティ
- Scalability
--  The files work well on limited hardware, and can take advantage of better hardware when it is available.
--  This ability is important because computers have different monitor resolutions and bit depths.
- 速さ
- Speed
--  The graphics described by SWF files render quickly.
- スクリプト対応
- Scriptability
--  The format includes tags that provide sequences of byte codes to be interpreted by a stack machine.
--  The byte codes support the ActionScriptR language.
--  Flash Player provides a runtime ActionScript object model that allows interaction with drawing primitives, servers, and features of Flash Player.

- SWF files have the extension .swf and a MIME type of application/x-shockwave-flash.
- The SWF format has evolved through several versions.
- SWF ファイルは .swf の拡張子と、application/x-shockwave-flash の MIME type を持つ。
- SWF フォーマットは幾つかのバージョンを通して発展している。
- Through SWF 5, substantial additions were made to the SWF tag set.
- Starting with SWF 6 and later, the SWF format changes less, as more new features are implemented partly or entirely at the ActionScript level.
- Starting with SWF 9, the ActionScript 3.0 language, which employs the new ActionScript Virtual Machine 2 (AVM2) can be used.
- Anyone planning to generate SWF file content that uses newer features should become familiar with the ActionScript object model that Flash Player exposes.
- Some references for this information are Programming ActionScript 3.0 (see www.adobe.com/go/learn_fl_cs4_programmingAS3_en), ActionScript 3.0 Language Reference (see www.adobe.com/go/learn_flashcs4_langref_en), and the Adobe ActionScript Virtual Machine 2 Overview (PDF file) at www.adobe.com/go/avm2overview.
- Adobe seriously considers all feedback to the SWF file format specification.
- E-mail any unclear or potentially erroneous information within the specification to Adobe at flashformat@adobe.com.
- All such email submissions shall be subject to the Submitted Materials guidelines in the Terms of Use at www.adobe.com/misc/copyright.html.

** What’s new in SWF 10 [#whats-new-swf10]

* Basic Data Types [#basic-data-types]

** Coordinates and twips [#cord-twips]

- SWF ファイルフォーマットは x-y 座標を(通常、twip と呼ばれる)整数で保存する。
- SWF ファイルフォーマットの twip は論理 pixel の 1/20 である。
- 論理 pixel はスクリーン上で(拡大縮小せずに)100% スケールで再生したときの pixel である。例えば、800 twips x 400 twips の長方形は、40 x 20 の論理 pixel にレンダリングされる。
- 少数点以下の pixel サイズはアンチエイリアシングで近似される。790x390 twips ( 39.5 x 19.5 pixels) は少しぼやけたエッジで表される。
- twips はサイズと精度の良い折衷案である。これによって、極小な座標を処理している間も、ズーミングやオブジェクトの正確な配置に際して、sub-pixel(訳注: 1 pixel 以下)に対する正確さがもたらされる。

- Coordinates in the SWF file format use the traditional graphics axes: x is horizontal and proceeds from minimum values at the left to maximum values at the right, and y is vertical and proceeds from minimum values at the top to maximum values at the bottom.

** Integer types and byte order [#int-byteorder]