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From "Philipp Koch" <philipp.k...@day.com>
Subject Re: tEXt chunk in PNG
Date Tue, 05 Aug 2008 06:56:31 GMT
> ps. Philipp: I think Ben was asking how to embed text metadata into a
> Png using the tEXt chunk, not how to draw text onto the image, which
> your example helpfully demonstrates.
yes, you are right. i should have read the questions more "carefully".
sorry for the noise...

regards,
philipp

On Tue, Aug 5, 2008 at 1:34 AM, Charles Matthew Chen
<charlesmchen@gmail.com> wrote:
> Hi Ben,
>
>   I've added the ability to read and write Png's text chunks (tEXt,
> zTXt, iTXt) in a controlled way.  I've added a unit test that
> demonstrates how to use this new feature:
>
> https://svn.apache.org/repos/asf/incubator/sanselan/trunk/src/test/java/org/apache/sanselan/formats/png/PngTextTest.java
>
>   This functionality will be in the next release.  You can also make
> yourself a snapshot build from the SVN repository.  Instructions on
> how to do that are in the FAQ:
>
> http://cwiki.apache.org/confluence/display/SANSELAN/FAQ
>
> Charles.
>
> ps. Philipp: I think Ben was asking how to embed text metadata into a
> Png using the tEXt chunk, not how to draw text onto the image, which
> your example helpfully demonstrates.
>
>
> On Mon, Aug 4, 2008 at 5:06 PM,  <Ben.Fears@generaldynamics.uk.com> wrote:
>> Hi,
>>
>>
>>
>> I have a couple of questions regarding Sanselan.
>>
>>
>>
>> Firstly is there a user forum for the project I can direct my queries
>> to?
>>
>>
>>
>> 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' +
>> xmlString;
>>
>>
>>
>>                        PngCrc pngCrc = new PngCrc();
>>
>>                        int iCRC = pngCrc.crc(txtString.getBytes(),
>> txtString.length());
>>
>>
>>
>>                        //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,
>> txtString.getBytes());
>>
>>
>>
>>                        String kw = txt.getKeyword();
>>
>>                        String tx = txt.getText();
>>
>>
>>
>>                        //How do I insert txt into pngImage?
>>
>>
>>
>>                        return pngImage;
>>
>>            }
>>
>>
>>
>> Regards,
>>
>>
>>
>> Ben
>>
>>
>>
>>
>>
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>

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