Examples of org.apache.flex.swf.tags.DefineBitsJPEG3Tag

org.apache.flex.swf.tags.DefineBitsJPEG3Tag

Represents a DefineBitsJPEG3 tag in a SWF file.

This tag defines a bitmap character with JPEG compression. This tag extends DefineBitsJPEG2, adding alpha channel (opacity) data. Opacity/transparency information is not a standard feature in JPEG images, so the alpha channel information is encoded separately from the JPEG data, and compressed using the ZLIB standard for compression. The data format used by the ZLIB library is described by Request for Comments (RFCs) documents 1950 to 1952.

The data in this tag begins with the JPEG SOI marker 0xFF, 0xD8 and ends with the EOI marker 0xFF, 0xD9. Before version 8 of the SWF file format, SWF files could contain an erroneous header of 0xFF, 0xD9, 0xFF, 0xD8 before the JPEG SOI marker.

In addition to specifying JPEG data, DefineBitsJPEG2 can also contain PNG image data and non-animated GIF89a image data.

If ImageData begins with the eight bytes 0x89 0x50 0x4E 0x47 0x0D 0x0A 0x1A 0x0A, the ImageData contains PNG data.
If ImageData begins with the six bytes 0x47 0x49 0x46 0x38 0x39 0x61, the ImageData contains GIF89a data.

If ImageData contains PNG or GIF89a data, the optional BitmapAlphaData is not supported.

    private DefineBitsTag buildImage(byte[] imageBytes, byte[] alphaBytes)
    {
        if (imageBytes == null || alphaBytes == null)
            return null;


        DefineBitsJPEG3Tag tag = new DefineBitsJPEG3Tag();
        tag.setImageData(imageBytes);
        tag.setBitmapAlphaData(alphaBytes);
        tag.setAlphaDataOffset(imageBytes.length);
        return tag;
    }

        final int id = bitStream.readUI16();
        final int alphaDataOffset = (int)bitStream.readUI32();
        final byte[] imageData = bitStream.read(alphaDataOffset);
        final byte[] bitmapAlphaData = bitStream.readToBoundary();


        final DefineBitsJPEG3Tag tag = new DefineBitsJPEG3Tag();
        tag.setCharacterID(id);
        tag.setAlphaDataOffset(alphaDataOffset);
        tag.setImageData(imageData);
        tag.setBitmapAlphaData(bitmapAlphaData);
        return tag;
    }

Related Classes of org.apache.flex.swf.tags.DefineBitsJPEG3Tag

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