"

 COPYRIGHT (c) 1991 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

"{ Package: 'stx:libview2' }"

ImageReader subclass:#GIFReader

	instanceVariableNames:'pass xpos ypos rowByteSize remainBitCount bufByte bufStream

		prefixTable suffixTable clearCode eoiCode freeCode codeSize

		maxCode interlace frameDelay iterationCount leftOffs topOffs'

	classVariableNames:'ImageSeparator Extension Terminator'

	poolDictionaries:''

	category:'Graphics-Images-Readers'

!

!GIFReader class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1991 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    this class provides methods for loading and saving GIF pictures.

    It has been tested with some different GIF87a pictures, I dont

    know, if it works with other GIF versions.

    GIF extension blocks are not handled.

    GIF file writing is not implemented (use TIFF).

    legal stuff extracted from GIF87a documentation:

    CompuServe Incorporated hereby grants a limited, non-exclusive, royalty-free

    license for the use of the Graphics Interchange Format(sm) in computer

    software; computer software utilizing GIF(sm) must acknowledge ownership of the

    Graphics Interchange Format and its Service Mark by CompuServe Incorporated, in

    User and Technical Documentation. 

      The Graphics Interchange Format(c) is the Copyright property of

      CompuServe Incorporated. GIF(sm) is a Service Mark property of

      CompuServe Incorporated.

    [See also:]

	Image Form Icon

	BlitImageReader FaceReader JPEGReader PBMReader PCXReader 

	ST80FormReader SunRasterReader TargaReader TIFFReader WindowsIconReader 

	XBMReader XPMReader XWDReader 

    [author:]

	Claus Gittinger

"

! !

!GIFReader class methodsFor:'initialization'!

initialize

    "install myself in the Image classes fileFormat table

     for the `.gif' extensions."

    ImageSeparator := $, codePoint.

    Extension := $!! codePoint.

    Terminator := $; codePoint.

    MIMETypes defineImageType:'image/gif' suffix:'gif' reader:self.

    "Modified: 14.10.1997 / 18:47:27 / cg"

! !

!GIFReader class methodsFor:'testing'!

canRepresent:anImage

    "return true, if anImage can be represented in my file format.

     GIF supports depth 8 images only."

    anImage depth == 8 ifTrue:[^ true].

    ('GIFReader [info]: images depth is ~~ 8.') infoPrintCR.

    ^ false.

    "Created: 17.10.1997 / 20:19:20 / cg"

!

isValidImageFile:aFileName

    "return true, if aFileName contains a GIF image"

    |id inStream|

    inStream := self streamReadingFile:aFileName.

    inStream isNil ifTrue:[^ false].

    inStream text.

    id := String new:6.

    inStream nextBytes:6 into:id.

    inStream close.

    (id = 'GIF87a') ifFalse:[

	(id startsWith:'GIF') ifFalse:[^ false].

	id ~= 'GIF89a' ifTrue:[ 

	    'GIFReader [info]: not a GIF87a/GIF89a file - hope that works' infoPrintCR.

	]

    ].

    ^ true

    "Modified: 10.1.1997 / 15:40:34 / cg"

! !

!GIFReader methodsFor:'private-reading'!

makeGreyscale

    "not yet implemented/needed"

!

readColorMap:colorMapSize

    "get a gif colormap consisting of colorMapSize entries"

    |rgbVector|

    rgbVector := inStream nextBytes:colorMapSize*3.

    ^ MappedPalette rgbBytesVector:rgbVector 

!

readExtension:aStream

    "get gif89 extension"

    |type blockSize subBlockSize

     aspNum aspDen left top width height cWidth cHeight fg bg

     animationType animationTime animationMask

     appID appAUTH

     b ok|

    type := aStream nextByte.

    type == $R codePoint ifTrue:[

        "/

        "/ Ratio extension

        "/

        'GIFREADER [info]: ratio extension ignored' infoPrintCR.

        blockSize := aStream nextByte.

        (blockSize == 2) ifTrue:[

            aspNum := aStream nextByte.

            aspDen := aStream nextByte

        ] ifFalse:[

            aStream skip:blockSize

        ].

        "/ eat subblocks

        [(subBlockSize := aStream nextByte) > 0] whileTrue:[

            aStream skip:subBlockSize

        ].

        ^ self

    ].

    type == 16r01 ifTrue:[

        "/

        "/ plaintext extension

        "/

"/        'GIFREADER [info]: plaintext extension ignored' infoPrintCR.

        subBlockSize := aStream nextByte.

        left := aStream nextShortMSB:false.

        top := aStream nextShortMSB:false.

        width := aStream nextShortMSB:false.

        height := aStream nextShortMSB:false.

        cWidth := aStream nextByte.

        cHeight := aStream nextByte.

        fg := aStream nextByte.

        bg := aStream nextByte.

        aStream skip:12.

        [(subBlockSize := aStream nextByte) > 0] whileTrue:[

            aStream skip:subBlockSize

        ].

        ^ self

    ].

    type == 16rF9 ifTrue:[

        "/

        "/ graphic control extension

        "/

"/        'GIFREADER [info]: graphic control extension' infoPrintCR.

        [(subBlockSize := aStream nextByte) ~~ 0] whileTrue:[

            "/ type bitAnd:1 means: animationMask is transparent pixel

            "/ to be implemented in Image ...

            animationType := aStream nextByte.

            animationTime := aStream nextShortMSB:false.

            animationMask := aStream nextByte.

            subBlockSize := subBlockSize - 4.

           (animationType bitTest: 1) ifTrue:[

                maskPixel := animationMask.

"/                'GIFREADER [info]: mask: ' infoPrint. (maskPixel printStringRadix:16) infoPrintCR.

            ].

"/            'GIFREADER [info]: animationTime: ' infoPrint. (animationTime * (1/100)) infoPrintCR.

"/            'GIFREADER [info]: animationType: ' infoPrint. (animationType) infoPrintCR.

"/            'GIFREADER [info]: animationMask: ' infoPrint. (animationMask) infoPrintCR.

            frameDelay := (animationTime * (1/100)) * 1000.

            subBlockSize ~~ 0 ifTrue:[

                aStream skip:subBlockSize

            ].

        ].

        ^ self

    ].

    type == 16rFE ifTrue:[

        "/

        "/ comment extension

        "/

"/        'GIFREADER [info]: comment extension ignored' infoPrintCR.

        [(blockSize := aStream nextByte) ~~ 0] whileTrue:[

            aStream skip:blockSize

        ].

        ^ self

    ].

    type == 16rFF ifTrue:[

        "/

        "/  application extension

        "/

        subBlockSize := aStream nextByte.

        appID := (aStream nextBytes:8 ) asString.

        appAUTH := aStream nextBytes:3.

        subBlockSize := aStream nextByte.

        ok := false.

        appID = 'NETSCAPE' ifTrue:[

            appAUTH asString = '2.0' ifTrue:[

                subBlockSize == 3 ifTrue:[

                    b := aStream nextByte.

                    iterationCount := aStream nextShortMSB:false.

                    subBlockSize := aStream nextByte.

                    ok := true.

"/                    ('GIFREADER [info]: NETSCAPE application extension - iterationCount = ') infoPrint.

"/                    iterationCount infoPrintCR.

                ]

            ]

        ].

        ok ifFalse:[

            ('GIFREADER [info]: application extension (' , appID , ') ignored') infoPrintCR.

        ].

        [subBlockSize > 0] whileTrue:[

            aStream skip:subBlockSize.

            subBlockSize := aStream nextByte.

        ].

        ^ self

    ].

    type == 16r2C ifTrue:[

        "/

        "/  image descriptor extension

        "/

        "/ 'GIFREADER [info]: image descriptor extension ignored' infoPrintCR.

        [(subBlockSize := aStream nextByte) > 0] whileTrue:[

            aStream skip:subBlockSize

        ].

        ^ self

    ].

    "/

    "/ unknown extension

    "/

    'GIFREADER [info]: unknown extension ignored' infoPrintCR.

    [(subBlockSize := aStream nextByte) > 0] whileTrue:[

        aStream skip:subBlockSize

    ]

    "Modified: / 1.4.1998 / 15:01:18 / cg"

!

readImage:aStream

    "read a single image from aStream."

    | flag interlaced hasLocalColorMap bitsPerPixel colorMapSize

     codeLen compressedData compressedSize index count h tmp srcOffset dstOffset

     initialBuffSize|

    "get image data"

    leftOffs := aStream nextShortMSB:false.

    topOffs := aStream nextShortMSB:false.

"/    'GIFReader: leftOffs ' infoPrint. leftOffs infoPrintCR.

"/    'GIFReader: topOffs ' infoPrint. topOffs infoPrintCR.

    width := aStream nextShortMSB:false.

    height := aStream nextShortMSB:false.

    self reportDimension.

"/

"/    'width ' print. width printNewline.

"/    'height ' print. height printNewline.

"/

    "another flag byte"

    flag := aStream nextByte.

    interlaced :=           (flag bitAnd:2r01000000) ~~ 0.

    hasLocalColorMap :=     (flag bitAnd:2r10000000) ~~ 0.

    "localColorMapSorted := (flag bitAnd:2r00100000) ~~ 0.      "

    "if image has a local colormap, this one is used"

    hasLocalColorMap ifTrue:[

        "local descr. overwrites"

        bitsPerPixel := (flag bitAnd:2r00000111) + 1.

        colorMapSize := 1 bitShift:bitsPerPixel.

        "overwrite colormap"

        colorMap := self readColorMap:colorMapSize.

    ].

    "get codelen for decompression"

    codeLen := aStream nextByte.

    (aStream respondsTo:#fileSize) ifTrue:[

        initialBuffSize := aStream fileSize.

    ] ifFalse:[

        initialBuffSize := 512.

    ].

    compressedData := ByteArray uninitializedNew:initialBuffSize.

    "get compressed data"

    index := 1.

    count := aStream nextByte.

    [count notNil and:[count ~~ 0]] whileTrue:[

        (compressedData size < (index+count)) ifTrue:[

            |t|

            t := ByteArray uninitializedNew:(index+count*3//2).

            t replaceBytesFrom:1 to:index-1 with:compressedData startingAt:1.

            compressedData := t.

        ].

        aStream nextBytes:count into:compressedData startingAt:index blockSize:4096.

        index := index + count.

        count := aStream nextByte

    ].

    compressedSize := index - 1.

    h := height.

    data := ByteArray new:((width + 1) * (h + 1)).

"/    'GIFReader: decompressing ...' infoPrintCR.

    self class decompressGIFFrom:compressedData

                           count:compressedSize

                            into:data

                      startingAt:1

                         codeLen:(codeLen + 1).

    interlaced ifTrue:[

"/    'GIFREADER: deinterlacing ...' infoPrintCR.

        tmp := ByteArray new:(data size).

        "phase 1: 0, 8, 16, 24, ..."

        srcOffset := 1.

        0 to:(h - 1) by:8 do:[:dstRow |

            dstOffset := dstRow * width + 1.

            tmp replaceFrom:dstOffset to:(dstOffset + width - 1)

                       with:data startingAt:srcOffset.

            srcOffset := srcOffset + width.

        ].

        "phase 2: 4, 12, 20, 28, ..."

        4 to:(h - 1) by:8 do:[:dstRow |

            dstOffset := dstRow * width + 1.

            tmp replaceFrom:dstOffset to:(dstOffset + width - 1)

                       with:data startingAt:srcOffset.

            srcOffset := srcOffset + width.

        ].

        "phase 3: 2, 6, 10, 14, ..."

        2 to:(h - 1) by:4 do:[:dstRow |

            dstOffset := dstRow * width + 1.

            tmp replaceFrom:dstOffset to:(dstOffset + width - 1)

                       with:data startingAt:srcOffset.

            srcOffset := srcOffset + width.

        ].

        "phase 4: 1, 3, 5, 7, ..."

        1 to:(h - 1) by:2 do:[:dstRow |

            dstOffset := dstRow * width + 1.

            tmp replaceFrom:dstOffset to:(dstOffset + width - 1)

                       with:data startingAt:srcOffset.

            srcOffset := srcOffset + width.

        ].

        data := tmp.

        tmp := nil.

    ].

    "Created: / 13.1.1998 / 10:44:05 / cg"

    "Modified: / 12.8.1998 / 13:55:32 / cg"

! !

!GIFReader methodsFor:'private-writing'!

assignTransparentPixelIn:image

    "find an usused pixelValue in the colorMap (or image)."

    (cmap := image colorMap) size > 0 ifTrue:[

    ].

    usedPixelValues := image usedValues.

!

checkCodeSize

    (freeCode > maxCode and: [codeSize < 12])

	    ifTrue: 

		    [codeSize := codeSize + 1.

		    maxCode := (1 bitShift: codeSize) - 1]

    "Created: 14.10.1997 / 18:42:01 / cg"

!

flushBits

	remainBitCount = 0

		ifFalse: 

			[self nextBytePut: bufByte.

			remainBitCount := 0].

	self flushBuffer

    "Modified: 14.10.1997 / 18:58:06 / cg"

!

flushBuffer

    bufStream isEmpty ifTrue: [^ self].

    outStream nextPut: bufStream size.

    outStream nextPutAll: bufStream contents.

    bufStream := WriteStream on: (ByteArray new: 256)

    "Modified: 14.10.1997 / 20:46:04 / cg"

!

flushCode

	self flushBits

    "Created: 14.10.1997 / 18:57:33 / cg"

!

nextBitsPut: anInteger

        | integer writeBitCount shiftCount |

        shiftCount := 0.

        remainBitCount = 0

                ifTrue:

                        [writeBitCount := 8.

                        integer := anInteger]

                ifFalse:

                        [writeBitCount := remainBitCount.