Well, transparency in GIFS is handled throught the pallete, you
can assign an entry to be transparent. Since I have no clue how the
ACME GIF encoder goes from 32 bit Alpha RGB to an 8bit pallete, this
is a bit hard to answer, but I would hope that they might have an API
to control/suggest an output pallete (and what entries should be
transparent) in which case you should be able to tell it to make the
background color transparent.
Since the real question is given an Alpha RGB image how do I
get the ACME encoder to output a transparent GIF, I would think you
would have more luck asking the ACME people...
Sorry,
TK> On Thursday 14 June 2001 00:54, Roland Schulz wrote:
>> Hey,
>>
>> I don't think my problem is caused by batik, but it is very clause
>> related. I would like to rasterize so that all browser show the
>> transparency. Since transparent png's aren't supported by the
>> Internet Explorer, I want to use gif's instead (in my case it
>> doesn't matter that gif don't support alpha transparency, because I
>> only want the background to be transparent). To do this I wrote a
>> GIFTranscoder with the following function.
>>
>> public void writeImage(BufferedImage img, TranscoderOutput output)
>> throws TranscoderException { OutputStream ostream =
>> output.getOutputStream(); new GifEncoder (img, ostream).encode ();
>> }
>>
>> As GifEncoder I use the one from Acme
>> (http://www.acme.com/java/software/). This way I can rasterize
>> gif's but they aren't transparent! Somehow the alpha channel is for
>> all pixels read in by the encoder set to 255, even though this svg
>> works with the PNGTranscoder. I don't use any filters (e.g. to
>> reduce the colors - right know the image doesn't have to much
>> colors). It looks to me that the ColorModel or the ImageConsumer
>> which are used by the Encoder somehow mess up the Alpha
>> channel. But the Acme Encoder is suppose to support transparent
>> gif's. It sets all pixels with alpha < 128 to the transparent
>> color. But since alpha is somehow always 255 it doesnt work. Does
>> anyone know if it really supports transparent gif's? Has anyone
>> generated transparent gif's before?
>>
>> I also tried the Gif89Encoder version (jmge.net/java/gifenc) and
>> the pja (www.eteks.com/pja/en/) version, with the same results.
TK> I have no clue sorry. Anyway, if you find the answer, please let
TK> me know :)
TK> Thierry.
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