ImageGear for Java
GIF Non-Image Data Structure
| ImageGear for Java User Guide > ImageGear Imaging Formats Reference > ImageGear Supported Non-Image Data > GIF Non-Image Data Structure |
GIF file format is complex and has different non-image data that can be stored before and after an image data. The GIF metadata design allows you to read/write any GIF non-image data and prevents from misunderstanding with GIF extensions storing order.
The following metadata are always saved before an image data:
All other GIF Extensions Metadata are saved before an image data.
ImageGear represents simpler GIF metadata by single metadata items, and more complex metadata by subtrees. Thus, there are two main GIF metadata levels in ImageGear:
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| GIF header level | ||||||
| GIF Logical Screen Descriptor level | ||||||
| GIF Image Descriptor level | ||||||
|
optional Global and/or Local Color Tables and optional GIF Extensions levels (extensions before image) | ||||||
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "GIFHeader" | 0x10 | Tree | 0 | NULL | 0 | TRUE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "Signature" | 0x101 | Leaf | STRING | "GIF" | 3 | TRUE |
| "Version" | 0x102 | Leaf | STRING | 3 | TRUE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "LogicalScreenDescriptor" | 0x20 | Tree |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "LogicalScreenWidth" | 0x201 | Leaf | UINT16 | 1 | FALSE | |
| "LogicalScreenHeight" | 0x202 | Leaf | UINT16 | 1 | FALSE | |
| "Fields" | 0x205 | Tree | ||||
| "GlobalColorTableFlag" | 0x206 | Leaf | BOOL | 1 | FALSE | |
| "ColorResolution" | 0x207 | Leaf | UINT8 | 1 | FALSE | |
| "SortFlag" | 0x208 | Leaf | BOOL | 1 | FALSE | |
| "GlobalColorTableSize" | 0x209 | Leaf | UINT8 | 1 | FALSE | |
| "Fields" | 0x205 | Tree | ||||
| "BackgroundColorIndex" | 0x203 | Leaf | UINT8 | FALSE | ||
| "PixelAspectRatio" | 0x204 | Leaf | UINT8 | FALSE | ||
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "GlobalColorTable" | 0x30 | Leaf | RAW_DATA | Variable | TRUE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "ImageDescriptor" | 0x2C | Tree |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "ImageLeftPosition" | 0x2C1 | Leaf | UINT16 | 1 | FALSE | |
| "ImageTopPosition" | 0x2C2 | Leaf | UINT16 | 1 | FALSE | |
| "ImageWidth" | 0x2C3 | Leaf | 1 | FALSE | ||
| "ImageHeight" | 0x2C4 | Leaf | 1 | FALSE | ||
| "Fields" | 0x2C5 | Tree |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "LocalColorTableFlag" | 0x2C6 | Leaf | BOOL | 1 | FALSE | |
| "InterlaceFlag" | 0x2C7 | Leaf | BOOL | 1 | FALSE | |
| "SortFlag" | 0x2C8 | Leaf | BOOL | 1 | FALSE | |
| "LocalColorTableSize" | 0x2C9 | Leaf | UINT8 | 1 | FALSE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "LocalColorTable" | 0x40 | Leaf | RAW_DATA | Variable | TRUE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "GraphicControlExtension" | 0xF9 | Tree |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "Fields" | 0xF91 | Tree | ||||
| "DisposalMethod" | 0xF92 | Leaf | UINT8 | 1 | FALSE | |
| "UserInputFlag" | 0xF93 | Leaf | BOOL | 1 | FALSE | |
| "TransparentColorFlag" | 0xF94 | Leaf | BOOL | 1 | FALSE | |
| "Fields" | 0xF91 | Tree | ||||
| "DelayTime" | 0xF95 | Leaf | UINT16 | 1 | FALSE | |
| "TransparentColorIndex" | 0xF96 | Leaf | UINT8 | 1 | FALSE | |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "CommentExtension" | 0xFE | Leaf | STRING | Variable | TRUE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "ApplicationExtension" | 0xFF | Tree |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "ApplicationIdentifier" | 0xFF1 | Leaf | STRING | 8 | FALSE | |
| "Appl.AuthenticationCode" | 0xFF2 | Leaf | UINT8 | 4 | FALSE | |
| "ApplicationData" | 0xFF3 | Leaf | RAW_DATA | Variable | FALSE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "PlainTextExtension" | 0x01 | Tree | 0 | NULL | 0 | TRUE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "TextGridLeftPosition" | 0x11 | Leaf | UINT16 | 1 | FALSE | |
| "TextGridTopPosition" | 0x12 | Leaf | UINT16 | 1 | FALSE | |
| "TextGridWidth" | 0x13 | Leaf | UINT16 | 1 | FALSE | |
| "TextGridHeight" | 0x14 | Leaf | UINT16 | 1 | FALSE | |
| "CharacterCellWidth" | 0x15 | Leaf | UINT8 | 1 | FALSE | |
| "CharacterCellHeight" | 0x16 | Leaf | UINT8 | 1 | FALSE | |
| "TextForegroundColorIndex" | 0x17 | Leaf | UINT8 | 1 | FALSE | |
| "TextBackgroundColorIndex" | 0x18 | Leaf | UINT8 | 1 | FALSE | |
| "PlainTextData" | 0x19 | Leaf | STRING | Variable | FALSE |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| "AfterImageExtensions" | 0xFFF | Tree |
| Name | Id | Type | Value Type | Value | Value Length | Read Only |
| One or more GIF extension levels | ||||||