"

 COPYRIGHT (c) 1996 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:#PNGReader

	instanceVariableNames:'colorType depth compressionMethod filterMethod interlaceMode

		redBytes greenBytes blueBytes'

	classVariableNames:''

	poolDictionaries:''

	category:'Graphics-Images-Support'

!

!PNGReader class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1996 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 PNG pictures.

    It is currenty untested.

    [See also:]

        Image Form Icon

        BlitImageReader FaceReader GIFReader JPEGReader PBMReader PCXReader 

        ST80FormReader SunRasterReader TargaReader TIFFReader WindowsIconReader 

        XBMReader XPMReader XWDReader 

    [author:]

        Claus Gittinger

"

! !

!PNGReader class methodsFor:'initialization'!

initialize

    "install myself in the Image classes fileFormat table

     for the `.png' extension."

    Image addReader:self suffix:'png'.

    "Modified: 1.2.1997 / 15:02:47 / cg"

! !

!PNGReader class methodsFor:'testing'!

isValidImageFile:aFileName

    "return true, if aFileName contains a PNG image"

    |inStream magic|

    inStream := self streamReadingFile:aFileName.

    inStream isNil ifTrue:[^ false].

    inStream binary.

    magic := ByteArray new:8.

    inStream nextBytes:8 into:magic.

    inStream close.

    ^ (magic = #[137 80 78 71 13 10 26 10])

    "Modified: 21.6.1996 / 20:38:46 / cg"

! !

!PNGReader methodsFor:'private'!

getChunk

    |len type crc|

    inStream atEnd ifTrue:[^ false].

    len := inStream nextLongMSB:true.

    type := String new:4.

    (inStream nextBytes:4 into:type) ~~ 4 ifTrue:[^ false].

"/ 'len: ' print. len print. ' type: ' print. type printCR.

    type = 'IEND' ifTrue:[^ false].

    (self processChunk:type len:len) ifFalse:[^ false].

    inStream skip:4.

"/    crc := inStream nextLongMSB:true.

    ^ true

    "Created: 21.6.1996 / 21:09:36 / cg"

    "Modified: 21.6.1996 / 21:20:26 / cg"

!

getIHDRChunk

    |len type crc|

    len := inStream nextLongMSB:true.

    type := String new:4.

    inStream nextBytes:4 into:type.

    type = 'IHDR' ifFalse:[self halt. ^ false].

    len == 13 ifFalse:[self halt. ^ false].

    width := inStream nextLongMSB:true.        

    height := inStream nextLongMSB:true.        

    (width <= 0 or:[height <= 0]) ifTrue:[

        'PNGReader: invalid dimension(s)' infoPrintCR.

        ^ false.

    ].

    depth := inStream nextByte.

    colorType := inStream nextByte.

    compressionMethod := inStream nextByte.

    filterMethod := inStream nextByte.

    interlaceMode := inStream nextByte.

    inStream skip:4.

"/    crc := inStream nextLongMSB:true.

    ^ true

    "Modified: 21.6.1996 / 21:38:35 / cg"

!

processBKGDChunkLen:len

    inStream skip:len.

    ^ true

    "Created: 21.6.1996 / 21:15:49 / cg"

!

processChunk:type len:len

    type = 'gAMA' ifTrue:[^ self processGAMAChunkLen:len].

    type = 'sBIT' ifTrue:[^ self processSBITChunkLen:len].

    type = 'tEXt' ifTrue:[^ self processTEXTChunkLen:len].

    type = 'IDAT' ifTrue:[^ self processIDATChunkLen:len].

    type = 'tIME' ifTrue:[^ self processTIMEChunkLen:len].

    type = 'bKGD' ifTrue:[^ self processBKGDChunkLen:len].

    type = 'zTXt' ifTrue:[^ self processZTXTChunkLen:len].

    type = 'PLTE' ifTrue:[^ self processPLTEChunkLen:len].

    ('PNGReader: unrecognized chunk: ' , type , ' ignored.') infoPrintCR.

    inStream skip:len.

    ^ true.

    "Created: 21.6.1996 / 21:10:37 / cg"

    "Modified: 21.6.1996 / 21:22:37 / cg"

!

processGAMAChunkLen:len

    inStream skip:len.

    ^ true

    "Created: 21.6.1996 / 21:10:52 / cg"

!

processIDATChunkLen:len

    inStream skip:len.

    ^ true

    "Created: 21.6.1996 / 21:15:35 / cg"

!

processPLTEChunkLen:len

    |n "{ Class: SmallInteger }"|

    (len \\ 3) ~~ 0 ifTrue:[

        'PNGReader: invalid size of PLTE chunk' infoPrintCR.

        ^ false

    ].

    n := len // 3.

    redBytes := ByteArray new:n.

    greenBytes := ByteArray new:n.

    blueBytes := ByteArray new:n.

    1 to:n do:[:i |

        redBytes at:i put:(inStream nextByte).

        greenBytes at:i put:(inStream nextByte).

        blueBytes at:i put:(inStream nextByte)

    ].

    ^ true

    "Created: 21.6.1996 / 21:22:28 / cg"

    "Modified: 21.6.1996 / 21:43:01 / cg"

!

processSBITChunkLen:len

    inStream skip:len.

    ^ true

    "Created: 21.6.1996 / 21:13:09 / cg"

!

processTEXTChunkLen:len

    inStream skip:len.

    ^ true

    "Modified: 21.6.1996 / 21:15:27 / cg"

!

processTIMEChunkLen:len

    inStream skip:len.

    ^ true

    "Created: 21.6.1996 / 21:15:43 / cg"

    "Modified: 21.6.1996 / 21:20:42 / cg"

!

processZTXTChunkLen:len

    inStream skip:len.

    ^ true

    "Created: 21.6.1996 / 21:15:58 / cg"

! !

!PNGReader methodsFor:'reading from file'!

fromStream:aStream

    "read a stream containing a PNG image.

     Leave image description in instance variables."

    |header|

    inStream := aStream.

    aStream binary.

    "GIF-files are always msb (network-world)"

    byteOrder := #msb.

    header := ByteArray new:8.

    aStream nextBytes:8 into:header.

    header ~= #[137 80 78 71 13 10 26 10] ifTrue:[

        'PNGReader: not a png file.' infoPrintCR.

        ^ nil

    ].

    (self getIHDRChunk) ifFalse:[

        'PNGReader: required IHDR chunk missing.' infoPrintCR.

        ^ nil

    ].

    compressionMethod ~~ 0 ifTrue:[

        ('PNGReader: compressionMethod ' , compressionMethod printString , ' not supported.') infoPrintCR.

        ^ nil

    ].

    filterMethod > 0 ifTrue:[

        'PNGReader: invalid filterMethod' infoPrintCR.

        ^ nil.

    ].

    interlaceMode > 1 ifTrue:[

        'PNGReader: invalid interlaceMode' infoPrintCR.

        ^ nil.

    ].

    colorType == 0 ifTrue:[

        photometric := #blackIs0.

        samplesPerPixel := 1.

        bitsPerSample := Array with:depth.

    ] ifFalse:[ colorType == 2 ifTrue:[

        depth < 8 ifTrue:[

            'PNGReader: invalid colorType/depth combination' infoPrintCR.

            ^ nil.

        ].

        photometric := #rgb.

        samplesPerPixel := 3.

        bitsPerSample := Array with:depth with:depth with:depth.

    ] ifFalse:[ colorType == 3 ifTrue:[

        depth == 16 ifTrue:[

            'PNGReader: invalid colorType/depth combination' infoPrintCR.

            ^ nil.

        ].

        photometric := #palette.

        samplesPerPixel := 1.

        bitsPerSample := Array with:depth.

    ] ifFalse:[ colorType == 4 ifTrue:[

        depth < 8 ifTrue:[

            'PNGReader: invalid colorType/depth combination' infoPrintCR.

            ^ nil.

        ].

        photometric := #blackIs0.

        samplesPerPixel := 2.

        bitsPerSample := Array with:depth with:depth.

    ] ifFalse:[ colorType == 6 ifTrue:[

        depth < 8 ifTrue:[

            'PNGReader: invalid colorType/depth combination' infoPrintCR.

            ^ nil.

        ].

        photometric := #rgb.

        samplesPerPixel := 4.

        bitsPerSample := Array with:depth with:depth with:depth with:depth.

    ] ifFalse:[

        ('PNGReader: invalid colorType: ' , colorType printString , '.') infoPrintCR.

        ^ nil

    ]]]]].

    [self getChunk] whileTrue:[ ].

    photometric == #palette ifTrue:[

        redBytes isNil ifTrue:[

            'PNGReader: missing palette chunk.' infoPrintCR.

            ^ nil

        ].

        colorMap := Colormap 

                        redVector:redBytes 

                        greenVector:greenBytes 

                        blueVector:blueBytes.

    ].

    self halt.

    "

     PNGReader fromFile:'/home/cg/libpng-0.89c/pngtest.png'

    "

    "Modified: 21.6.1996 / 21:44:34 / cg"

! !

!PNGReader class methodsFor:'documentation'!

version

    ^ '$Header: /cvs/stx/stx/libview2/PNGReader.st,v 1.2 1997-02-01 14:05:19 cg Exp $'

! !

PNGReader initialize!