USAGE-NOTES.md

1 - First, we have to load the JP2 native library. This is crucial because the JNI native library depends on it :

System.load("absolute/path/to/openjpegLib")

2 - Then, we instantiate an OpenJPEGJavaDecoder object by passing it the absolute path to the JNI native library :

OpenJPEGJavaDecoder decoder = new OpenJPEGJavaDecoder("absolute/path/to/openjpegjniLib")` . 

Optionally, we can pass it an implementation of the interface IJavaJ2KDecoderLogger to be able to get logs from the C code.

3 - At this point, we have 2 choices :

• either we pass parameters to the decoder similar to passing parameters to opj_decompress, via decoder.setDecoderArguments(args)
• or we pass the input stream to be decoded directly, via decoder.setInputStream(byte[]).

Note that if the input stream is a JPT / JPIP stream, we must also call decoder.setInputIsJPT(). Also, we must set the output format via a call to decoder.setOutputFormat(String), knowing that the only supported format for the output is BMP as explained in the README.

4 - Finally, we call decoder.decodeJ2KtoImage(). In case we passed an input stream to the decoder, we shall get the output as a byte array by calling decoder.getOutputStreamBytes().