[Geotools-gt2-users] Help with generating a GeoTiff image with transparent pixels

[JoeK <joe...@ya...>]

Hi all,

I am trying to generate a GeoTiff image using GeoTools 2.7.1

The original image is a BufferedImage with RGB and Alpha channel.
(I can write the original image to a png file and it shows the transparent
pixels.)
(I used "Eye of GNOME" to view the tiff file.)
In the resulting tiff file, the transparent pixels are not transparent but
in blue color.

Here is the code I have:

      // setup
      Envelope2D bbox = new Envelope2D(crs("EPSG:4326"), west, south, width,
height);
      GridCoverageFactory factory = new GridCoverageFactory();
      // "img" is a java.awt.image.BufferedImage with RGB and Alpha channel
      GridCoverage2D coverage = factory.create("tiff", img, bbox);

      final File output = new File("out.tif");
      GeoTiffWriter gtwriter = new GeoTiffWriter(output);

      // sets transparency metadata
     
gtwriter.setMetadataValue(Integer.toString(BaselineTIFFTagSet.TAG_BITS_PER_SAMPLE),
"8");
     
gtwriter.setMetadataValue(Integer.toString(BaselineTIFFTagSet.TAG_SAMPLES_PER_PIXEL),
"4");
     
gtwriter.setMetadataValue(Integer.toString(BaselineTIFFTagSet.TAG_PLANAR_CONFIGURATION),
                               
Integer.toString(BaselineTIFFTagSet.PLANAR_CONFIGURATION_CHUNKY));
     
gtwriter.setMetadataValue(Integer.toString(BaselineTIFFTagSet.TAG_PHOTOMETRIC_INTERPRETATION),
                               
Integer.toString(BaselineTIFFTagSet.PHOTOMETRIC_INTERPRETATION_RGB));
     
gtwriter.setMetadataValue(Integer.toString(BaselineTIFFTagSet.TAG_EXTRA_SAMPLES),
                               
Integer.toString(BaselineTIFFTagSet.EXTRA_SAMPLES_ASSOCIATED_ALPHA));

      gtwriter.write(coverage, null);
      gtwriter.dispose();
      coverage.dispose(true);


Anyone knows if I missed a metadata for the GeoTiffWriter? Or if I set
something wrong in the metadata value?

Any advice is appreciated.
Thanks in advance.

- Joe

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