358 lines
9.4 KiB
Haxe
358 lines
9.4 KiB
Haxe
package iron.format.gif;
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import haxe.io.Bytes;
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/**
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* Gif data.
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*/
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typedef Data =
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{
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/**
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* Gif version. There is only 2 Gif version exists. 87a and 89a.
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* 87a have less features and does not support any extensions.
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* Unknown version is adviced to be interpreted as newest (89a) official version.
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*/
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var version:Version;
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/**
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* Information about logical screen of Gif that provides basic information about Gif.
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*/
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var logicalScreenDescriptor:LogicalScreenDescriptor;
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/**
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* Global color table used for Gif. Present only if Logical Screen Descriptor contained global color table flag.
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* Note that this color table not always present since frames can contain local color tables that overrides global color table.
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*/
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@:optional var globalColorTable:Null<ColorTable>;
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/**
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* List of Gif data blocks.
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*/
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var blocks:List<Block>;
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}
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/**
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* Gif data block. Custom blocks are not supported.
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*/
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enum Block
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{
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/**
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* Gif frame block.
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* Note that this block does not contain link to graphic control extension of Frame even if it is present. GraphicControl extension Block commonly present right before frame Block.
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*/
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BFrame(frame:Frame);
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/**
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* Additional extension block. This Block does not supported in 87a Gif specification version.
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*/
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BExtension(extension:Extension);
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/**
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* End of File block. Represents end of Gif data.
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*/
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BEOF;
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}
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/**
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* Extension block contains additional data about Gif image. This block does not supported by 87a version.
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*/
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enum Extension
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{
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/**
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* Graphic Control extension gives additional control over next frame, like frame delay, disposal method, alpha channel and other information.
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*/
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EGraphicControl(gce:GraphicControlExtension);
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/**
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* Commentary extension. Not show up as any visual, just a text in file.
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*/
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EComment(text:String);
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/**
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* Text extension. Must work as text rendering on the image, but ignored by all major Gif decoders.
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*/
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EText(pte:PlainTextExtension);
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/**
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* Application extension allow to insert additional application data into Gif. Mostly used app extension is NETSCAPE2.0 looping extension, used to set up amount of loops in frame.
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*/
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EApplicationExtension(ext:ApplicationExtension);
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/**
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* Unknown extension.
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*/
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EUnknown(id:Int, data:Bytes);
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}
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/**
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* Application extension. Mostly used only for one reason - setting up loops count. There is exist other app extensions but they are really rare.
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*/
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enum ApplicationExtension
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{
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/**
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* NETSCAPE2.0 looping extension. Contains only amount of animation repeats.
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* Note that there is two NETSCAPE2.0 app extensions for Gif format and the type of extension is stored in first byte of data. Looping extension have ID 1.
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*/
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AENetscapeLooping(loops:Int);
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/**
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* Unknown or unsupported app extension.
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*/
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AEUnknown(name:String, version:String, data:Bytes);
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}
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/**
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* Typical color table for Gif image.
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* Can contain 2, 4, 8, 16, 32, 64, 128 or 256 colors.
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* Data stored in RGB format. Information about alpha channel provided by Graohic Control Extension.
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*/
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typedef ColorTable = Bytes;
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/**
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* Single frame of the image.
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* Actually it's a merge of 3 consequent blocks:
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* 1. Image Descriptor.
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* Contains frame informations like position, size, existing of local color table and interlaced flag.
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* 2. [Local color table].
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* Only present if Image Descriptor contains local color table flag. Overrides global color table.
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* 3. Pixel data blocks.
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* LZW compressed pixel data.
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*/
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typedef Frame =
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{
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/**
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* X position of image on the Logical Screen
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*/
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var x:Int;
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/**
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* Y position of image on the Logical Screen
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*/
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var y:Int;
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/**
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* Width of image in pixels
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*/
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var width:Int;
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/**
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* Height of image in pixels
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*/
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var height:Int;
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/**
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* Is this image uses local color table?
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*/
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var localColorTable:Bool;
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/**
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* Is this image written in interlace mode?
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* Note: The pixel data already deinterlaced and this flag presented only for information purpose (and for Writer when there is one).
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*/
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var interlaced:Bool;
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/**
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* Is local color table sorted in order of decreasing priority?
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*/
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var sorted:Bool;
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/**
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* Size of local color table
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*/
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var localColorTableSize:Int;
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/**
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* Pixel data of frame. Stored as Indexed colors, 1 byte per pixel.
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*/
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var pixels:Bytes;
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/**
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* Local color table used by frame. Stored as 3-byte RGB colors. If value is null, must be used global color table.
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*/
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var colorTable:ColorTable;
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}
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/**
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* Graphic Control Extension block, used for setting up disposal method, transparency, delay and user input.
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*/
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typedef GraphicControlExtension =
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{
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/**
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* Disposal method of frame.
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*/
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var disposalMethod:DisposalMethod;
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/**
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* Is image must wait for user input, before dispose?
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* This flag may be used by user-defined program but absolutely ignored by any Gif players.
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*/
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var userInput:Bool;
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/**
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* Is image have transparency?
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*/
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var hasTransparentColor:Bool;
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/**
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* Delay, before next image appears. Delay is in centiseconds (1 centisecond = 1/100 seconds).
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* Note: Some players (like FastStone) cut fraction of elapsed time when progressing to next frame which results in small timing error.
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* Recommended to use `time -= delay` instead of `time = 0`.
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*/
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var delay:Int;
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/**
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* Index in color table that used as transparent.
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*/
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var transparentIndex:Int;
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}
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/**
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* Extension for rendering text on Gif logical screen. It does not supported by major Gif decoders.
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* Font and text size decision is left to decoder. (recommended to decide based on grid/cell size)
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* Text must be rendered with one character at cell.
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* It's recommended to replace any characters less than 0x20 and greater than 0xf7 to be rendered as Space (0x20)
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*/
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typedef PlainTextExtension =
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{
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/**
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* X position of text grid on Logical Screen.
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*/
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var textGridX:Int;
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/**
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* Y position of text grid on Logical Screen.
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*/
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var textGridY:Int;
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/**
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* Width of text grid in pixels.
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*/
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var textGridWidth:Int;
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/**
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* Height of text grid in pixels.
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*/
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var textGridHeight:Int;
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/**
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* Width of character cell in text grid.
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*/
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var charCellWidth:Int;
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/**
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* Height of character cell in text grid.
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*/
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var charCellHeight:Int;
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/**
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* Foreground/character color index.
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*/
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var textForegroundColorIndex:Int;
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/**
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* Background color index.
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*/
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var textBackgroundColorIndex:Int;
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/**
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* Text to render.
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*/
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var text:String;
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}
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/**
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* Logical screen descriptor of GIF file.
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* Contains very basic information about Gif.
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*/
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typedef LogicalScreenDescriptor =
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{
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/**
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* Width of GIF image in pixels
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*/
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var width:Int;
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/**
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* Height of GIF image in pixels
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*/
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var height:Int;
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/**
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* Is this file uses global color table?
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*/
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var hasGlobalColorTable:Bool;
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/**
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* Specification:
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* Number of bits per primary color available
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to the original image, minus 1. This value represents the size of
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the entire palette from which the colors in the graphic were
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selected, not the number of colors actually used in the graphic.
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For example, if the value in this field is 3, then the palette of
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the original image had 4 bits per primary color available to create
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the image. This value should be set to indicate the richness of
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the original palette, even if not every color from the whole
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palette is available on the source machine.
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*/
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var colorResolution:Int;
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/**
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* Specification:
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* Indicates whether the Global Color Table is sorted.
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If the flag is set, the Global Color Table is sorted, in order of
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decreasing importance. Typically, the order would be decreasing
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frequency, with most frequent color first. This assists a decoder,
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with fewer available colors, in choosing the best subset of colors;
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the decoder may use an initial segment of the table to render the
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graphic.
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*/
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var sorted:Bool;
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/**
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* Size of global color table.
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*/
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var globalColorTableSize:Int;
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/**
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* Background color index in global color table
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*/
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var backgroundColorIndex:Int;
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/**
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* Factor used to compute an approximation of the aspect ratio of the pixel in the original image.
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*/
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var pixelAspectRatio:Float;
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}
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/**
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* Version of Gif file.
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* The only 2 official versions is GIF87a and GIF89a.
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*/
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enum Version
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{
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/**
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* First version of Gif file format from May 1987.
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*
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* Note: The checking of unsupported blocks disabled by default to save some time. To enable supported blocks check set `yagp_strict_version_check` debug variable.
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*/
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GIF87a;
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/**
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* Second and actual version of Gif file format from July 1989.
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*/
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GIF89a;
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/**
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* Unknown version of Gif file.
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*/
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Unknown(version:String);
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}
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/**
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* Disposal method of GIF frame.
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*/
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enum DisposalMethod
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{
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/**
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* The disposal method is unspecified. Action on demand of viewer.
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*
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* Mostly interpreted as NO_ACTION.
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*/
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UNSPECIFIED;
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/**
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* No action required.
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*/
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NO_ACTION;
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/**
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* Fill frame rectangle with background color.
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*
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* Usage note:
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* Most renderers clears to transparency instead of filling background color, when frame's transparent color index not equals to background color index.
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*/
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FILL_BACKGROUND;
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/**
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* Render previous state of gif as it before rendering disposing frame.
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*/
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RENDER_PREVIOUS;
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/**
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* Reserved disposal methods.
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*/
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UNDEFINED(index:Int);
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}
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