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From <>
Subject tEXt chunk in PNG
Date Mon, 04 Aug 2008 15:06:12 GMT


I have a couple of questions regarding Sanselan. 


Firstly is there a user forum for the project I can direct my queries


Secondly, I would like to know if Sanselan is at the point where a tEXt
chunk can be inserted into a PNG image. If so, how is this done? I have
been using v0.94 but I can't make it do what I need.


I wish to embed an XML String containing meta data describing the image
file. I have written the function below. I think I have generated the
PNGChunktEXt correctly but without seeing an example I am not sure. If
it is correct, I still I don't know how to get it into the byte array
holding the png image.


I would appreciate any advice you could give.


            static public byte [] changePngMetadata(byte [] pngImage,
String xmlString) throws ImageReadException, IOException



                        String txtString = "TcsMetaData" + '\0' +


                        PngCrc pngCrc = new PngCrc();

                        int iCRC = pngCrc.crc(txtString.getBytes(),


                        //May want to use compressed text instead. Do I
need to compress the text string separately?

                        PNGChunktEXt txt = new
PNGChunktEXt(txtString.length(), PngConstants.tEXt, iCRC,


                        String kw = txt.getKeyword();

                        String tx = txt.getText();             


                        //How do I insert txt into pngImage?


                        return pngImage;                        







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