SWF_FILE_FORMAT_SPEC_V10文檔翻譯
Chapter 1 Basic Data Types
Coordinates and twips
The SWF file format stores all x-y coordinates as integers, usually in a unit of measurement
called a twip. In the SWF format, a twip is 1/20th of a logical pixel. A logical pixel is the same
as a screen pixel when the file is played at 100%—that is, without scaling.
座標及twips單位
SWF文件的X,Y座標是以整型格式進行存儲，通常以twips作爲一個量度單位，以SWF格式來說，
一個twip就相當於是一個邏輯像素的1/20，在沒有縮放，即100%比例進行播放時，一個SWF文件
邏輯像素就是一個屏幕像素。
Integer types and byte order
The SWF file format uses 8-bit, 16-bit, 32-bit, 64-bit, signed, and unsigned integer types. All
integer values are stored in the SWF file by using little-endian byte order: the least significant
byte is stored first, and the most significant byte is stored last, in the same way as the Intel x86
architecture. The bit order within bytes in the SWF file format is big-endian: the most
significant bit is stored first, and the least significant bit is stored last.
整型類型及字節序
SWF文件格式使用8位，16爲，32爲，64位，有符號及無符號整型類型，在SWF文件中，所有以整型
方式存儲的值都是使用little-endian 字節序，即低字節存儲在低位，高字節存儲在高位。Intel x86架構
採用得就是這種方式，而對於一個字節內位順序採用的是big-endian方式，及高位先存儲，然後再存低位。
MATRIX record
The MATRIX record represents a standard 2x3 transformation matrix of the sort commonly
used in 2D graphics. It is used to describe the scale, rotation, and translation of a graphic
object. The MATRIX record must be byte aligned.
MATRIX record表示的是標準的2×3排序變換矩陣，通常應用於2D，用來完成縮放，旋轉及圖形圖像變換
MATRIX record必須是字節對齊的。
|
Field |
Type |
Comment |
|
HasScale |
UB[1] |
Has |
|
NScaleBits If HasScale = 1 |
UB[5] Bits in each scale value field |
NScaleBits If HasScale = 1 |
|
ScaleX |
If HasScale = 1, FB[NScaleBits] x scale value |
ScaleX If HasScale = 1 |
|
ScaleY |
If HasScale = 1, FB[NScaleBits] y scale value |
ScaleY If HasScale = 1 |
|
HasRotate |
UB[1] |
Has rotate and skew values if equal to 1 |
|
NRotateBits |
If HasRotate = 1,UB[5] Bits in each rotate value field |
NRotateBits If HasRotate = 1 |
|
RotateSkew0 |
If HasRotate = 1, FB[NRotateBits] |
First rotate and skew value |
|
RotateSkew1 |
If HasRotate = 1, FB[NRotateBits] |
Second rotate and skew value |
|
NTranslateBits |
UB[5] |
Bits in each translate value field |
|
TranslateX |
SB[NTranslateBits] |
x translate value in twips |
|
TranslateY |
SB[NTranslateBits] |
y translate value in twips |
Chapter 2 SWF Structure Summary
The SWF header+SWF file structure
SWF File Header
Field Type Comment Bytes
Signature UI8 Signature byte: 1
“F” indicates uncompressed
“C” indicates compressed (SWF 6 and later only)
Signature UI8 Signature byte always “W” 1
Signature UI8 Signature byte always “S”
Version UI8 Single byte file version (for example, 0x06 for SWF 6) 1
FileLength UI32 Length of entire file in bytes 4
FrameSize RECT Frame size in twips 由表示最大數所需要位來決定
(前五位用來標識用多少位表示，因爲UB[5]
,注意單位是twips,換算成像素，還要除以20)
FrameRate UI16 Frame delay in 8.8 fixed number of frames per second 2
FrameCount UI16 Total number of frames in file 2
SWF file structure
Following the header is a series of tagged data blocks. All tags share a common format, so any
program parsing a SWF file can skip over blocks it does not understand. Data inside the block
can point to offsets within the block, but can never point to an offset in another block. This
ability enables tags to be removed, inserted, or modified by tools that process a SWF file.
The FileAttributes tag is only required for SWF 8 and later.
|Header | FileAttributes tag | Tag | Tag | Tag | End tag
Tag format
Each tag begins with a tag type and a length. The tag-header formats can be either short or
long. Short tag headers are used for tags with 62 bytes of data or less. Long tag headers, with a
signed 32-bit length field, can be used for any tag size up to 2GB, far larger than is presently
practical.
每一個tag都是以tag type+長度方式開始的，tag-header格式可以是 short 或 long 類型。Short
Tag headers 用來表示長度小於等於62字節的tag.Long tag headers是一個有符號的32-bit字段，
最大能存儲2GB長度Tag,這遠比目前實際大得多。
RECORDHEADER (short)
|
Field |
Type |
Comment |
|
TagCodeAndLength |
UI16 |
Upper 10 bits: tag type Lower 6 bits: tag length |
The length specified in the TagCodeAndLength field does not include the
RECORDHEADER that starts a tag.
在TagCodeAndLength字段中所標明的標籤的長度是不包含RECORDHEADER部分的，
If the tag is 63 bytes or longer, it is stored in a long tag header. The long tag header consists of
a short tag header with a length of 0x3f, followed by a 32-bit length.
如果tag是63字節或更長，它以long tag header方式來存儲，log tag header由一個shrot tag header+0x3f+32-bit length來組成。
RECORDHEADER (long)
|
Field |
Type |
Comment |
|
TagCodeAndLength |
UI16 |
Tag type and length of 0x3F Packed together as in short header |
|
Length |
SI32 |
Length of tag |
Definition and control tags
The two categories of tags in a SWF file are as follows:
"Definition tags" And "Control tags"
Definition tags -- define the content of the SWF file—the shapes, text, bitmaps, sounds, and so
on. Each definition tag assigns a unique ID called a character ID to the content it defines.
Flash Player then stores the character in a repository called the dictionary. Definition tags, by
themselves, do not cause anything to be rendered
Definition tags -- 定義SWF文件的內容--形狀，文本，位圖，聲音等等，每一個 definition tag被分配一個唯一
的ID好來表明一個已定義的內容，之後Flash Player將其存放在一個叫做“字典”的容器中，
Definition tag其自身不會被渲染。
Control tags -- create and manipulate rendered instances of characters in the dictionary, and
control the flow of the file.
Control tags -- 創建並操作字典中已渲染的角色實例，並控制文件數據流。
Tag ordering in SWF files（SWF文件中tag規則）
Generally speaking, tags in a SWF can occur in any order. However, you must observe the
following rules:
■ The FileAttributes tag must be the first tag in the SWF file for SWF 8 and later.
■ A tag should only depend on tags that come before it. A tag should never depend on a tag
that comes later in the file.
■ A definition tag that defines a character must occur before any control tag that refers to
that character.
一個定義了角色的definition tag必須出現在任何與該角色相關control tag之前。
■ Streaming sound tags must be in order. Out-of-order streaming sound tags result in the
sound being played out of order.
流聲音tag必須是有序的，無序的流聲音tag會導致播放時無序
■ The End tag is always the last tag in the SWF file.
The dictionary
The dictionary is a repository of characters that are defined, and are available for control tags
to use. The process of building and using the dictionary is as follows:
字典是所有被定義角色容器，爲control tags所用，建立及使用字典步驟如下：
1. The definition tag defines some content, such as a shape, font, bitmap, or sound.
2. The definition tag assigns a unique CharacterId to the content.
3. The content is saved in the dictionary under the CharacterId.
4. A control tag uses the CharacterId to retrieve the content from the dictionary, and performs
some action on the content, such as displaying a shape, or playing a sound.
Every definition tag must specify a unique ID. Duplicate IDs are not allowed. Typically, the
first CharacterId is 1, the second CharacterId is 2, and so on. The number zero (0) is special
and is considered a null character.
每一個定義的 definition tag 必須制定一個唯一的ID, 負責IDs 是不允許的，通常，第一個角色ID爲1，其次爲2，以此類推。
0用來表明空角色ID標識。
Control tags are not the only tags that reference the dictionary. Definition tags can use
characters from the dictionary to define more complex characters. For example, the
DefineButton and DefineSprite tags refer to other characters to define their contents. The
DefineText tag can refer to font characters to select different fonts for the text.
不僅僅Control tag能引用字典，definition tags也可以從字典中使用角色來定義更復雜的角色。例如：...
Processing a SWF file(SWF文件的處理)
Flash Player processes all of the tags in a SWF file until a ShowFrame tag is encountered. At
this point, the display list is copied to the screen and Flash Player is idle until it is time to
process the next frame. The contents of the first frame are the cumulative effect of performing
all of the control tag operations before the first ShowFrame tag. The contents of the second
frame are the cumulative effect of performing all of the control tag operations from the
beginning of the file to the second ShowFrame tag, and so on.
Flash Player在遇到 ShowFrame tag之前會處理所有的control tag,正因爲如此，顯示列表中的信息會被拷貝到屏幕上同時
Flash Player處於閒置狀態，直到遇到下一個ShowFrame tag出現。每個ShowFrame tag中取出的control tag在顯示的時候
呈現疊加效果
Summary
A SWF file is made up of a header, followed by a number of tags. The two types of tags are
definition tags and control tags. Definition tags define the objects known as characters,
which are stored in the dictionary. Control tags manipulate characters, and control the flow
of the file.
小結：
一個SWF文件由 header+ much more tags 組成，tags有兩種類型：definition tags 和 control tags,
Definition tags定義角色對象，並存儲在字典中，Control tags操作角色，並且控制文件數據流。
Chapter 3 The Display List(第三章，顯示列表)
Displaying a frame of a SWF file is a three-stage process:
1. Objects are defined with definition tags such as DefineShape, DefineSprite, and so on.
Each object is given a unique ID called a character, and is stored in a repository called the
dictionary.
2. Selected characters are copied from the dictionary and placed on the display list, which is
the list of the characters that will be displayed in the next frame.
3. Once complete, the contents of the display list are rendered to the screen with ShowFrame.
顯示一個swf 文件的一幀數據需要經歷三個步驟：
1：用definition tags（諸如defineShape, DefineSprite）等對對象進行定義，每一個對象分配一個唯一的ID標識一個角色並存儲在字典中
2：所選擇的角色從字典中拷貝出來並放置在顯示列表中，以方便下一幀顯示
3：完成以後，顯示列表中的信息就會在遇到ShowFrame標籤時進行渲染。
A depth value is assigned to each character on the display list. The depth determines the
stacking order of the character. Characters with lower depth values are displayed underneath
characters with higher depth values. A character with a depth value of 1 is displayed at the
bottom of the stack. A character can appear more than once in the display list, but at different
depths. Only one character can be at any given depth.
In SWF 1 and 2, the display list was a flat list of the objects that are present on the screen at
any given time. In SWF 3 and later versions, the display list is a hierarchical list where an
element on the display can have a list of child elements. For more information, see
DefineSprite.
depth 值被分配給顯示列表中的每個角色，這個 depth 值決定角色的棧順序，角色的depth值越小，出現的就越晚。
最小的之爲1，放置在棧底，一個角色可以在顯示列表中出現多次，但是有不同的depths，一個角色對應一個給定的depth
,在SWF1和2版本中，顯示列表是對象平坦列表被展現在屏幕上，SWF3及後續版本改用繼承的方式，詳見DefineSprite.
The following six tags are used to control the display list:
■ PlaceObject： Adds a character to the display list.
■ PlaceObject2 & PlaceObject3： Adds a character to the display list, or modifies the
character at the specified depth.
■ RemoveObject： Removes the specified character from the display list.
■ RemoveObject2： Removes the character at the specified depth.
■ ShowFrame： Renders the contents of the display list to the display.
NOTE
The older tags, PlaceObject and RemoveObject, are rarely used in SWF 3 and
later versions.
Clipping layers[裁剪層]
Flash Player supports a special kind of object in the display list called a clipping layer. A
character placed as a clipping layer is not displayed; rather it clips (or masks) the characters
placed above it. The ClipDepth field in PlaceObject2 specifies the top-most depth that the
clipping layer masks.
For example, if a shape was placed at depth 1 with a ClipDepth of 4, all depths above 1, up to
and including depth 4, are masked by the shape placed at depth 1. Characters placed at depths
above 4 are not masked.
Flash Player在顯示列表中提供了一種特殊的對象類型叫裁剪層，一個角色放置在裁剪層中是不會被顯示的，而是裁剪
（或遮蓋）放置在其上的對象，在PlaceObject2就有一個ClipDepth字段用來表明裁剪的最大層級數。
Using the display list[顯示列表的使用]
The following procedure creates and displays an animation:
接下來的步驟是創建及顯示一個動畫
1. Define each character with a definition tag.
Each character is given a unique character ID, and added to the dictionary.
爲每一個角色分配一個definition tag，每一個角色分配一個唯一ID,並放置在字典中
2. Add each character to the display list with a PlaceObject2 tag. Each PlaceObject2 tag
specifies the character to be displayed, plus the following attributes:
A depth value, which controls the stacking order of the character being placed. Characters
with lower depth values appear to be underneath characters with higher depth values. A
depth value of 1 means the character is displayed at the bottom of the stack. Only one
character can be at any given depth.
A transformation matrix, which determines the position, scale, factor, and angle of
rotation of the character being placed. The same character can be placed more than once
(at different depths) with a different transformation matrix.
變換矩陣，決定位置，縮放，比例，旋轉角度，同樣的角色可以放置不同的變換矩陣。
An optional color transform, which specifies the color effect applied to the character
being placed. Color effects include transparency and color shifts.
An optional name string, which identifies the character being placed for SetTarget
actions. SetTarget is used to perform actions inside sprite objects.
An optional ClipDepth value, which specifies the top-most depth that will be masked by
the character being placed.
An optional ratio value, which controls how a morph character is displayed when placed.
A ratio of zero displays the character at the start of the morph. A ratio of 65535 displays
the character at the end of the morph.
3. Use a ShowFrame tag to render the contents of the display list to the screen.
4. Use a PlaceObject2 tag to modify each character on the display List.
Each PlaceObject2 assigns a new transformation matrix to the character at a given depth.
The character ID is not specified because each depth can have only one character.
使用PlaceObject2 tag來修改顯示列表中的每一個角色
每一個PlaceObject2分配一個新的變換矩陣給指定depth的角色
角色ID是不能指定的，因爲每一個depth只能對應一個角色。
5. Use a ShowFrame tag to display the characters in their new positions.
Repeat steps 4 and 5 for each frame of the animation.
6. Use a RemoveObject2 tag to Remove each character from the display list.
Only the depth value is required to identify the character being removed.
Display list tags
Display list tags are used to add character and character attributes to a display list.
PlaceObject2
The PlaceObject2 tag extends the functionality of the PlaceObject tag. The PlaceObject2 tag
can both add a character to the display list, and modify the attributes of a character that is
already on the display list. The PlaceObject2 tag changed slightly from SWF 4 to SWF 5. In
SWF 5, clip actions were added.
The tag begins with a group of flags that indicate which fields are present in the tag. The
optional fields are CharacterId, Matrix, ColorTransform, Ratio, ClipDepth, Name, and
ClipActions. The Depth field is the only field that is always required.
The depth value determines the stacking order of the character. Characters with lower depth
values are displayed underneath characters with higher depth values. A depth value of 1 means
the character is displayed at the bottom of the stack. Any given depth can have only one
character. This means a character that is already on the display list can be identified by its
depth alone (that is, a CharacterId is not required).
The PlaceFlagMove and PlaceFlagHasCharacter tags indicate whether a new character is
being added to the display list, or a character already on the display list is being modified. The
meaning of the flags is as follows:
■ PlaceFlagMove = 0 and PlaceFlagHasCharacter = 1
A new character (with ID of CharacterId) is placed on the display list at the specified
depth. Other fields set the attributes of this new character.
■ PlaceFlagMove = 1 and PlaceFlagHasCharacter = 0
■ PlaceFlagMove = 1 and PlaceFlagHasCharacter = 1
The character at the specified Depth is removed, and a new character (with ID of
CharacterId) is placed at that depth. Other fields set the attributes of this new character.
For example, a character that is moved over a series of frames has PlaceFlagHasCharacter set
in the first frame, and PlaceFlagMove set in subsequent frames. The first frame places the new
character at the desired depth, and sets the initial transformation matrix. Subsequent frames
replace the transformation matrix of the character at the desired depth.
The optional fields in PlaceObject2 have the following meaning:
■ The CharacterId field specifies the character to be added to the display list. CharacterId is
used only when a new character is being added. If a character that is already on the display
list is being modified, the CharacterId field is absent.
■ The Matrix field specifies the position, scale and rotation of the character being added
or modified.
■ The ColorTransform field specifies the color effect applied to the character being added
or modified.
■ The Ratio field specifies a morph ratio for the character being added or modified. This
field applies only to characters defined with DefineMorphShape, and controls how far the
morph has progressed. A ratio of zero displays the character at the start of the morph. A
ratio of 65535 displays the character at the end of the morph. For values between zero and
65535 Flash Player interpolates between the start and end shapes, and displays an inbetween
shape.
■ The ClipDepth field specifies the top-most depth that will be masked by the character
being added. A ClipDepth of zero indicates that this is not a clipping character.
■ The Name field specifies a name for the character being added or modified. This field is
typically used with sprite characters, and is used to identify the sprite for SetTarget
actions. It allows the main file (or other sprites) to perform actions inside the sprite (see
“Sprites and Movie Clips” on page 231).
■ The ClipActions field, which is valid only for placing sprite characters, defines one or
more event handlers to be invoked when certain events occur.
Chapter 4 Control tags
Control tags manage some overall aspects of files, frames, and playback in SWF files.
Control tags是針對SWF文件幀，回放等宏觀，全局的一些方面進行管理
包含的tag如下：
SetBackgroundColor
FrameLabel
Protect
End
ExportAssets
ImportAssets
EnableDebugger
EnableDebugger2
ScriptLimits
SetTabIndex
FileAttributes
|
Field |
Type |
Comment |
|
UseGPU (see note following table) |
UB[1] |
If 1, the SWF file uses GPU compositing features when drawing graphics, where such acceleration is available. If 0, the SWF file will not use hardware accelerated graphics facilities. Minimum file version is 10. |
ImportAssets2
SymbolClass
Metadata
DefineScalingGrid
DefineSceneAndFrameLabelData
Chapter 5 Actions
Actions are an essential part of an interactive SWF file. Actions allow a file to react to events
such as mouse movements or mouse clicks. The SWF 3 action model and earlier supports a
simple action model. The SWF 4 action model supports a greatly enhanced action model that
includes an expression evaluator, variables, and conditional branching and looping. The
SWF 5 action model adds a JavaScript-style object model, data types, and functions.
行爲對於相與SWF文件進行互動是必須的一部分，行爲允許SWF文件對事件作出反應(如鼠標移動或鼠標點擊事件)，SWF 3 action model以及早期版本支持一些簡單的行爲模型，SWF 4 action model支持的行爲模型有了很大增強，包括表達式計算，變量，條件分支及循環，SWF 5 action model 還添加了java script風格的腳本，數據類型及函數
SWF 3 action model
The SWF 3 action model consists of eleven instructions for Flash Player:
|
Instruction |
See |
Description |
|
Play |
ActionPlay |
Start playing at the current frame |
|
Stop |
ActionStop |
Stop playing at the current frame |
|
NextFrame |
ActionNextFrame |
Go to the next frame |
|
PreviousFrame |
ActionPreviousFrame |
Go to the previous frame |
|
GotoFrame |
ActionGotoFrame |
Go to the specified frame |
|
GotoLabel |
ActionGoToLabel |
Go to the frame with the specified label |
|
WaitForFrame |
ActionWaitForFrame |
Wait for the specified frame |
|
GetURL |
ActionGetURL |
Get the specified URL |
|
StopSounds |
ActionStopSounds |
Stop all sounds playing |
|
ToggleQuality |
ActionToggleQuality |
Toggle the display between high and low quality |
|
SetTarget |
ActionSetTarget |
Change the context of subsequent actions to a named object |
An action (or list of actions) can be triggered by a button state transition, or by SWF 3
actions. The action is not executed immediately, but is added to a list of actions to be
processed. The list is executed on a ShowFrame tag, or after the button state has changed. An
action can cause other actions to be triggered, in which case, the action is added to the list of
actions to be processed. Actions are processed until the action list is empty.
By default, Timeline actions such as Stop (see ActionStop), Play (see ActionPlay), and
GoToFrame (see ActionGotoFrame) apply to files that contain them. However, the SetTarget
action (see ActionSetTarget), which is called Tell Target in the Adobe Flash user interface, can
be used to send an action command to another file or sprite (see DefineSprite).
行爲（或行爲列表）可以通過按鈕狀態轉換或 SWF 3 actions 進行觸發，行爲不是立即被執行，而是被添加到行爲列表中執行，行爲列表在遇到 ShowFrame tag或按鈕狀態轉換後時執行，這種情況下，被添加到行爲列表中待執行的行爲會被全部處理直到行爲列表爲空爲止，
默認情況下，時間性行會作用於包含他們的文件，如（Stop, Play, GoToFrame等），SetTarget行爲或接口名TellTarget,可以被用來給另一個SWF文件或sprite發送action command.
SWF 3 actions
The actions in this section are available in SWF 3.[行爲僅適用於SWF 3版本]
ActionSetTarget
ActionSetTarget instructs Flash Player to change the context of subsequent actions, so they
apply to a named object (TargetName) rather than the current file.
For example, the SetTarget action can be used to control the Timeline of a sprite object. The
following sequence of actions sends a sprite called "spinner" to the first frame in its
Timeline:
1. SetTarget "spinner"
2. GotoFrame zero
3. SetTarget " " (empty string)
4. End of actions. (Action code = 0)
All actions following SetTarget “spinner” apply to the spinner object until SetTarget “”,
which sets the action context back to the current file. For a complete discussion of target
names see DefineSprite.
ActionSetTartget 行爲
ActionSetTarget 行爲表明Flash Player要去改變後續actions的上下文，因此比較適合應用於named object(TargetName)而不是當前SWF文件。
例如：他和SetTarget action可以用於控制sprite object 的生命線，一下行爲流程是將一個叫做spinner的Sprite發送給他生命線的第一幀上。
接着SetTarget “spinner”以下的所有行爲都將作用於spinner object直到遇到 Set Target “”, Set Target “”的作用是將行爲上下文返回當前文件，對於target names 的詳細討論請參見DefineSprite.
SWF 4 action model
The SWF 4 file format supports a greatly enhanced action model that includes an expression
evaluator, variables, conditional branching and looping.
Flash Player 4 incorporates a stack machine that interprets and executes SWF 4 actions. The
key SWF 4 action is ActionPush. This action is used to push one or more parameters onto the
stack. Unlike SWF 3 actions, SWF 4 actions do not have parameters embedded in the tag,
rather they push parameters onto the stack, and pop results off the stack.
The expression evaluator is also stack based. Arithmetic operators include ActionAdd,
ActionSubtract, ActionMultiply, and ActionDivide. The Flash authoring tool converts
expressions to a series of stack operations. For example, the expression 1+x*3 is represented as
the following action sequence:
ActionPush "x"
ActionGetVariable
ActionPush "3"
ActionMultiply
ActionPush "1"
ActionAdd
The result of this expression is on the stack.
SWF 4與之前最大的不同就是可以將參數壓入棧，像表達式計算就是基於棧來實現的。
Movie control [移動控制流]
ActionGetProperty
ActionGetProperty does the following:
1. Pops index off the stack.
2. Pops target off the stack.
3. Retrieves the value of the property enumerated as index from the movie clip with target
path target and pushes the value to the stack.
ActionGetProperty按一下方式執行：
1：從棧中彈出索引值
2：從棧中彈出target.
3:根據target path從影片剪輯中以枚舉索引值方式來獲取相關屬性值，並將結果壓入棧中。
The following table lists property index values. The _quality, _xmouse, _ymouse and _rotation 10
properties are available in SWF 5 and later.
以下列表中列出了屬性索引值，像質量，鼠標x,y座標及旋轉。這些在swf5及後續版本中支持。