'From Pharo6.0 of 13 May 2016 [Latest update: #60540] on 23 May 2018 at 11:28:36.06927 am'!
ImageReadWriter subclass: #GIFReadWriter
	instanceVariableNames: 'width height bitsPerPixel colorPalette rowByteSize xpos ypos pass interlace codeSize clearCode eoiCode freeCode maxCode prefixTable suffixTable remainBitCount bufByte bufStream transparentIndex mapOf32 localColorTable delay loopCount offset frames canvasWidth canvasHeight backgroundColorIndex'
	classVariableNames: 'Extension ImageSeparator Terminator'
	poolDictionaries: ''
	category: 'Graphics-Files'!

!GIFReadWriter methodsFor: 'private-decoding' stamp: 'EricGade 5/18/2018 17:36'!
readHeader
	| is89 byte hasColorMap |
	frames := OrderedCollection new. "For storing AnimatedImageFrames"
	(self hasMagicNumber: 'GIF87a' asByteArray) 
		ifTrue: [ is89 := false ]
		ifFalse: 
			[ (self hasMagicNumber: 'GIF89a' asByteArray) 
				ifTrue: [ is89 := true ]
				ifFalse: [ ^ self error: 'This does not appear to be a GIF file' ] ].
	"Width and Height for whole canvas, not
	just an invididual frame/form"
	canvasWidth := self readWord.
	canvasHeight := self readWord.
	byte := self next.
	hasColorMap := (byte bitAnd: 128) ~= 0.
	bitsPerPixel := (byte bitAnd: 7) + 1.
	backgroundColorIndex := self next.
	self next ~= 0 ifTrue: 
		[ is89 ifFalse: [ ^ self error: 'corrupt GIF file (screen descriptor)' ] ].
	hasColorMap 
		ifTrue: [ colorPalette := self readColorTable: (1 bitShift: bitsPerPixel) ]
		ifFalse: 
			[ "Transcript cr; show: 'GIF file does not have a color map.'."
			colorPalette := nil	"Palette monochromeDefault" ]! !

!GIFReadWriter methodsFor: 'private-decoding' stamp: 'EricGade 5/18/2018 16:04'!
readBody
	"Read the GIF blocks. Modified to return a form.  "
	| form extype block blocksize packedFields delay1 disposal frame |
	form := nil.
	frame := AnimatedImageFrame new.
	[ stream atEnd ] whileFalse: 
		[ block := self next.
		block = Terminator ifTrue: [ ^ form ].
		block = ImageSeparator 
			ifTrue: 
				[ form
					ifNil: [ 
						form := self readBitData.
						frame 
							form: form;
							offset: form offset ]
					ifNotNil: [ self skipBitData ] ]
			ifFalse: 
				[ block = Extension ifFalse: [ ^ form	"^ self error: 'Unknown block type'" ].
				"Extension block"
				extype := self next.	"extension type"
				extype = 249 
					ifTrue: 
						[ "graphics control"
						self next = 4 ifFalse: [ ^ form	"^ self error: 'corrupt GIF file'" ].
						"====
				Reserved                      3 Bits
				Disposal Method               3 Bits
				User Input Flag               1 Bit
				Transparent Color Flag        1 Bit
				==="
						packedFields := self next.
						disposal := self readDisposal: packedFields.
						delay1 := self next.	"delay time 1"
						delay := (self next * 256 + delay1) * 10.	"delay time 2"
						transparentIndex := self next.
						(packedFields bitAnd: 1) = 0 
							ifTrue: [ transparentIndex := nil ]
							ifFalse: [ 
								Transcript show: ('transparentBitSet for ',transparentIndex asString); cr].
						self next = 0 ifFalse: [ ^ form	"^ self error: 'corrupt GIF file'" ]. 
						frame
							form: form;
							delay: delay1 * 10; "We might need to use the other?"
							disposal: disposal.
						frames add: frame ]
					ifFalse: 
						[ "Skip blocks"
						[ (blocksize := self next) > 0 ] whileTrue: 
							[ "Read the block and ignore it and eat the block terminator"
							self next: blocksize ] ] ] ].
			frame form: form.
			frames add: frame.! !

!GIFReadWriter methodsFor: 'accessing' stamp: 'EricGade 5/18/2018 12:41'!
frames
	^ frames! !

!GIFReadWriter methodsFor: 'accessing' stamp: 'EricGade 5/18/2018 14:37'!
canvasHeight
	^ canvasHeight! !

!GIFReadWriter methodsFor: 'accessing' stamp: 'EricGade 5/18/2018 17:54'!
backgroundColor
	backgroundColorIndex ifNotNil: [ 
		colorPalette ifNotNil: [ 
			^ colorPalette at: backgroundColorIndex + 1]].
	^ Color transparent.! !

!GIFReadWriter methodsFor: 'accessing' stamp: 'EricGade 5/18/2018 14:37'!
canvasWidth
	^ canvasWidth! !

!GIFReadWriter methodsFor: 'as yet unclassified' stamp: 'EricGade 5/18/2018 16:01'!
readDisposal: aPackedByte
	"Read the three-bit disposal flag from
	the packed byte in the Graphic Control Extension block.
	Disposal is three-bits with the following codes:
	 |0 0 0 [0 0 0] 0 0|
	1 => leave current frame and draw on top of it (#leaveCurrent)
	2 => Restore to background color (#restoreBackground)
	3 => Restore to state before current frame was drawn (#restorePrevState)"
	| least middle both str |
	
	"This means both the least significant and middle
	bits are set, giving us 3"
	str := ''.
	((aPackedByte bitAnd: 16) = 16)
		ifTrue: [ str := str,'1' ]
		ifFalse: [ str := str,'0' ].
	((aPackedByte bitAnd: 8) = 8)
		ifTrue: [ str := str,'1' ]
		ifFalse: [ str := str,'0' ].
	((aPackedByte bitAnd: 4) = 4)
		ifTrue: [ str := str,'1' ]
		ifFalse: [ str := str,'0' ].
	Transcript show: str; cr.
	(both := (aPackedByte bitAnd: 12) = 12).
	both ifTrue: [ ^ #restorePrevState ].
	
	least := (aPackedByte bitAnd: 4) = 4.
	least ifTrue: [ ^ #leaveCurrent ].
	
	middle := (aPackedByte bitAnd: 8) = 8.
	middle ifTrue: [ ^ #restoreToBackground ].
	
	^ nil
	! !


!GIFReadWriter reorganize!
(#private updatePixelPosition checkCodeSize setParameters:)
(#'stream access' close)
(#'private-bits access' nextBitsPut: nextBits flushBits)
(#'private-decoding' readBitData readHeader readCode readWord readColorTable: skipBitData readBody)
(#'private-encoding' writeBitData: writeCode: readPixelFrom: flushCode writeWord: writeHeader writeCodeAndCheckCodeSize:)
(#'private-packing' fillBuffer peekByte nextBytePut: flushBuffer nextByte)
(#accessing nextImage understandsImageFormat frames canvasHeight delay: setStream: backgroundColor nextPutImage: canvasWidth loopCount:)
(#'as yet unclassified' readDisposal:)
!