"

 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.

"

ImageReader subclass:#GIFReader

	instanceVariableNames:'redMap greenMap blueMap pass xpos ypos rowByteSize remainBitCount

		bufByte bufStream prefixTable suffixTable clearCode eoiCode

		freeCode codeSize maxCode interlace'

	classVariableNames:'ImageSeparator Extension Terminator'

	poolDictionaries:''

	category:'Graphics-Images-Support'

!

!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 := $, asciiValue.

    Extension := $!! asciiValue.

    Terminator := $; asciiValue.

    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

    "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 - writing'!

assignTransparentPixelIn:image

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

    |cmap usedPixelValues|

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

        cmap size < 256 ifTrue:[

            maskPixel := cmap size.

            ^ self

        ]

    ].

    usedPixelValues := image usedValues.

    usedPixelValues size < (1 bitShift:image depth) ifTrue:[

        "/ there must be an unused pixelValue

        maskPixel := ((0 to:(1 bitShift:image depth)-1) asSet removeAll:(usedPixelValues)) first.

    ] ifFalse:[

        Image informationLostQuerySignal

            raiseWith:image

            errorString:('GIF writer cannot assign a transparent pixel - all pixelValues used by image').

    ]

!

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.

                        integer _ bufByte + (anInteger bitShift: 8 - remainBitCount)].

        [writeBitCount < codeSize]

                whileTrue:

                        [self nextBytePut: ((integer bitShift: shiftCount) bitAnd: 255).

                        shiftCount _ shiftCount - 8.

                        writeBitCount _ writeBitCount + 8].

        (remainBitCount _ writeBitCount - codeSize) = 0

                ifTrue: [self nextBytePut: (integer bitShift: shiftCount)]

                ifFalse: [bufByte _ integer bitShift: shiftCount].

        ^anInteger

    "Modified: 15.10.1997 / 16:50:30 / cg"

!

nextBytePut: aByte

        bufStream nextPut: aByte.

        bufStream size >= 254 ifTrue: [self flushBuffer]

    "Modified: 15.10.1997 / 16:50:52 / cg"

!

readPixelFrom: bits 

    | pixel |

    ypos >= height ifTrue: [^ nil].

    (maskPixel notNil 

    and:[(mask pixelAtX:xpos y:ypos) == 0]) ifTrue:[

        pixel := maskPixel

    ] ifFalse:[

        pixel := bits at: ypos * rowByteSize + xpos + 1.

    ].

    self updatePixelPosition.

    ^ pixel

    "Created: 14.10.1997 / 18:43:50 / cg"

    "Modified: 15.10.1997 / 16:46:43 / cg"

!

setParameters:bitsPerPixel 

    clearCode := 1 bitShift:bitsPerPixel.

    eoiCode := clearCode + 1.

    freeCode := clearCode + 2.

    codeSize := bitsPerPixel + 1.

    maxCode := (1 bitShift: codeSize) - 1

    "Modified: 14.10.1997 / 20:09:48 / cg"

!

updatePixelPosition

        (xpos _ xpos + 1) >= width ifFalse: [^ self].

        xpos _ 0.

        interlace == true

                ifFalse: 

                        [ypos _ ypos + 1.

                        ^ self].

        pass = 0

                ifTrue: 

                        [(ypos _ ypos + 8) >= height

                                ifTrue: 

                                        [pass _ pass + 1.

                                        ypos _ 4].

                        ^ self].

        pass = 1

                ifTrue: 

                        [(ypos _ ypos + 8) >= height

                                ifTrue: 

                                        [pass _ pass + 1.

                                        ypos _ 2].

                        ^ self].

        pass = 2

                ifTrue: 

                        [(ypos _ ypos + 4) >= height

                                ifTrue: 

                                        [pass _ pass + 1.

                                        ypos _ 1].

                        ^ self].

        pass = 3

                ifTrue: 

                        [ypos _ ypos + 2.

                        ^ self].

        ^ self error: 'can''t happen'

    "Modified: 14.10.1997 / 18:44:27 / cg"

!

writeCode: aCode 

    self nextBitsPut: aCode

    "Created: 14.10.1997 / 18:38:35 / cg"

    "Modified: 15.10.1997 / 17:01:47 / cg"

!

writeCodeAndCheckCodeSize: t1 

    self writeCode: t1.

    self checkCodeSize

    "Created: 14.10.1997 / 18:38:24 / cg"

    "Modified: 14.10.1997 / 18:40:56 / cg"

! !

!GIFReader methodsFor:'reading from file'!

checkGreyscaleColormap

    "return true, if colormap is actually a greymap.

     Could be used to convert it into a greyScale image - which is not yet done."

    |sz "{ Class: SmallInteger }"

     redVal|

    sz := redMap size.

    1 to:sz do:[:i |

        redVal := redMap at:i.

        redVal ~~ (greenMap at:i) ifTrue:[^ false].

        redVal ~~ (blueMap at:i) ifTrue:[^ false].

    ].

    ^ true

    "Modified: 2.5.1996 / 17:54:40 / cg"

!

fromStream:aStream

    "read a stream containing a GIF image.

     Leave image description in instance variables."

    |byte index flag count fileColorMap

     colorMapSize bitsPerPixel scrWidth scrHeight

     hasColorMap hasLocalColorMap interlaced id

     leftOffs topOffs codeLen

     compressedData compressedSize

     tmp srcOffset dstOffset isGif89 atEnd

     h "{ Class: SmallInteger }"|

    inStream := aStream.

    aStream binary.

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

    byteOrder := #lsb.

    id := ByteArray new:6.

    aStream nextBytes:6 into:id startingAt:1.

    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:[

            'GIFReader [info]: not a gif file' infoPrintCR.

            ^ nil

        ].

        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:[

        self readColorMap:colorMapSize.

        fileColorMap := Colormap 

                        redVector:redMap 

                        greenVector:greenMap 

                        blueVector:blueMap.

    ].

    colorMap := fileColorMap.

    photometric := #palette.

    samplesPerPixel := 1.

    bitsPerSample := #(8).

    atEnd := false.

    [atEnd] whileFalse:[

        "gif89a extensions"

        byte := aStream nextByte.

        byte == Extension ifTrue:[

            self readExtension:aStream.

        ] ifFalse:[

            (byte == Terminator) ifTrue:[

                atEnd := true

            ] ifFalse:[

                "must be image separator"

                (byte ~~ ImageSeparator) ifTrue:[

                    ('GIFReader [info]: corrupted gif file (no IMAGESEP): ' , (byte printStringRadix:16)) infoPrintCR.

                    ^ nil

                ].

                "get image data"

                leftOffs := aStream nextShortMSB:false.

                topOffs := aStream nextShortMSB:false.

                width := aStream nextShortMSB:false.

                height := aStream nextShortMSB:false.

                dimensionCallBack notNil ifTrue:[

                    dimensionCallBack value:self

                ].

"/

"/              '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"

                    self readColorMap:colorMapSize.

                    colorMap := Colormap 

                                    redVector:redMap 

                                    greenVector:greenMap 

                                    blueVector:blueMap.

                ] ifFalse:[

                    colorMap := fileColorMap

                ].

                "get codelen for decompression"

                codeLen := aStream nextByte.

                "get compressed data"

                index := 1.

                count := aStream nextByte.

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

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

                    index := index + count.

                    count := aStream nextByte

                ].

                compressedSize := index - 1.

                h := height.

                data := ByteArray uninitializedNew:((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 uninitializedNew:(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 |