"

 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.

    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.

    Notice:

        there has been some annoyance regarding a patent on the compression algorithm

        used in gif. This patent is now obsolete. However, there is no warranty from

        exept, regarding any legal problems, when using GIF.

        We therefore highly recommend to use newer (and especially: royalty-free) formats,

        such as PNG.

    [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:'image reading'!

fromStream:aStream

    "read a stream containing a GIF image (or an image sequence).

     Leave image description in instance variables."

    |byte index flag count fileColorMap

     colorMapSize bitsPerPixel scrWidth scrHeight

     hasColorMap hasLocalColorMap interlaced id

     codeLen

     compressedData compressedSize

     tmp srcOffset dstOffset isGif89 atEnd

     h "{ Class: SmallInteger }" 

     img firstImage firstOffset firstFrameDelay frame imageCount|

    inStream := aStream.

    aStream binary.

    "GIF-files are always lsb (intel-world)"

    byteOrder := #lsb.

    id := ByteArray new:6.

    (aStream nextBytes:6 into:id startingAt:1) ~~ 6 ifTrue:[

        ^ self fileFormatError:'not a gif file (short read)'.

    ].

    id := id asString.

    "all I had for testing where GIF87a files;

     I hope later versions work too ..."

    isGif89 := false.

    (id ~= 'GIF87a') ifTrue:[

        (id startsWith:'GIF') ifFalse:[

            ^ self fileFormatError:('not a gif file (id=''' , id , ''')').

        ].

        id ~= 'GIF89a' ifTrue:[ 

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

        ]

    ].

    "get screen dimensions (not used)"

    scrWidth := aStream nextShortMSB:false.

    scrHeight := aStream nextShortMSB:false.

    "get flag byte"

    flag := aStream nextByte.

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

    "bitsPerRGB :=     ((flag bitAnd:2r01110000) bitShift:-4) + 1. "

    "colorMapSorted := ((flag bitAnd:2r00001000) ~~ 0.             "

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

    colorMapSize := 1 bitShift:bitsPerPixel.

    "get background (not used)"

    aStream nextByte.

    "aspect ratio (not used)"

    aStream nextByte.

    "get colorMap"

    hasColorMap ifTrue:[

        fileColorMap := self readColorMap:colorMapSize.

    ].

    colorMap := fileColorMap.

    photometric := #palette.

    samplesPerPixel := 1.

    bitsPerSample := #(8).

    imageCount := 0.

    atEnd := false.

    [atEnd] whileFalse:[

        "gif89a extensions"

        byte := aStream nextByte.

        byte isNil ifTrue:[

            "/ atEnd-Terminator missing

            atEnd := true

        ] ifFalse:[

            byte == Extension ifTrue:[

"/ 'Ext' infoPrintCR.

                self readExtension:aStream.

            ] ifFalse:[

                (byte == Terminator) ifTrue:[

                    atEnd := true

                ] ifFalse:[

                    "must be image separator"

                    (byte ~~ ImageSeparator) ifTrue:[

                        ^ self fileFormatError:('corrupted gif file (no IMAGESEP): ' , (byte printStringRadix:16)).

                    ].

"/ 'Img' infoPrintCR.

                    fileColorMap notNil ifTrue:[

                        colorMap := fileColorMap.

                    ].

                    Object primitiveFailureSignal handle:[:ex |

                        ^ self fileFormatError:('corrupted gif file').

                    ] do:[

                        self readImage:aStream.

                    ].

                    maskPixel notNil ifTrue:[

                        "/

                        "/ ok, there is a maskValue

                        "/ build a Depth1Image for it.

                        "/

                        self buildMaskFromColor:maskPixel

                    ].

                    imageCount == 0 ifTrue:[

                        img := self makeImage.

                        "/ remember first image in case more come later.

                        firstImage := img.

                        firstFrameDelay := frameDelay.

                        firstOffset := (leftOffs @ topOffs).

                    ] ifFalse:[

                        imageCount == 1 ifTrue:[

                            imageSequence := ImageSequence new.

                            img imageSequence:imageSequence.

                            "/ add frame for first image.

                            frame := ImageFrame new image:firstImage.

                            frame delay:firstFrameDelay.

                            frame offset:firstOffset.

                            imageSequence add:frame.

                        ].  

                        img := self makeImage.

                        img imageSequence:imageSequence.

                        "/ add frame for this image.

                        frame := ImageFrame new image:img.

                        frame delay:frameDelay.

                        frame offset:(leftOffs @ topOffs).

                        imageSequence add:frame.

                    ].

                    imageCount := imageCount + 1.

                    frameDelay := nil.

                    aStream atEnd ifTrue:[

                        atEnd := true.

                    ]

                ]

            ].

        ].

    ].

    imageSequence notNil ifTrue:[

        iterationCount notNil ifTrue:[

            iterationCount == 0 ifTrue:[

                imageSequence loop:true.

            ] ifFalse:[

                imageSequence loop:false.

                imageSequence iterationCount:iterationCount.

            ]

        ]

    ].

    "

     Image fromFile:'/home/cg/work/stx/goodies/bitmaps/gifImages/animated/vrml.gif'

     Image fromFile:'/home/cg/work/stx/goodies/bitmaps/gifImages/animated/arrow.gif'

    "

    "Modified: / 5.7.1996 / 17:32:01 / stefan"

    "Modified: / 21.8.1998 / 22:20:00 / 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.

        "/ eat subblocks

        [(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 and:[subBlockSize notNil]] 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' infoPrintCR.

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

            aStream skip:blockSize

        ].

        ^ self

    ].

    type == 16rFF ifTrue:[

        "/

        "/  application extension

        "/

        "/ 'GIFREADER [info]: application extension' infoPrintCR.

        subBlockSize := aStream nextByte.

        appID := (aStream nextBytes:8 ) asString.

        appAUTH := aStream nextBytes:3.