This Java library supports fragmenting and reassembling Office Open XML (OOXML) formatted documents including Microsoft Office such as PowerPoint (pptx) or Word (docx) and Apache Open Office such as Presentations (odp) and Text (odt). Fragmenting documents into chunks is currently only supported on the desktop/server JDK. Reassembling document chunks is supported on both the desktop/server JDK and Android SDK.
Fragmenting a document produces multiple smaller copies of the document by reducing the resolution of the media embedded within the document. Each smaller copy of the document is called a chunk. Each chunk is complete in that it contains all of the text, formatting, and media from the original. The only difference between a chunk and its original document is that a portion of the data from each embedded image is removed - resulting in a lower resolution, yet still complete, copy of the image.
The fragmenting process is done in such a way that any two of the resulting fragments can be reassembled to produce a copy of the original with twice the resolution for each image. In this way, all of the chunks can be reassembled to restore the full quality of the original document.
The 'us.ihmc.chunking' package contains the 'Fragmenter' and 'Reassembler' interfaces that are meant to be applicable to any document type.
The 'us.ihmc.chunking.server' package includes the 'OoxmlFragmenter' and 'OoxmlReassembler' implemetation of the 'Fragmenter' and 'Reassembler' interfaces specific to Office Open XML documents. This implementation depends upon the 'javax.imageio' and 'java.awt.image' packages that are only currently available on the JDK and not the Android platform.
Example
String ooxmlPath = "some/path/document.pptx"; // path to the document to fragment
byte chunkCount = 4; // how many total chunks to fragment into 2, 4, 8, 16
byte chunkCompressionPercent = 100; // 0-100, 0=smallest size, 100=highest quality
byte[] originalFileData = Files.readAllBytes(ooxmlPath);
final String mimeType = FileUtils.getMimeTypeForFile(ooxmlPath);
Fragmenter fragmenter = new OoxmlFragmenter();
Collection<ChunkWrapper> chunks = fragmenter.fragment(originalFileData, mimeType, chunkCount, chunkCompressionPercent);
...
Collection<AnnotationWrapper> annotations = null; // not supported yet, future enhancement
Reassembler reassembler = new OoxmlReassembler();
byte[] reassembledFileData = reassembler.reassemble(chunks, annotations, mimeType, chunkCount, chunkCompressionPercent);
The 'us.ihmc.chunking.android' package includes the 'OoxmlReassembler' implemetation specific to Office Open XML documents. This implementation depends upon the 'android.graphics' package is only available on the Android platform and not the JDK.
Example
ArrayList<ChunkWrapper> chunkList = new ArrayList<ChunkWrapper>();
...
byte[] chunkFileData = OoxmlChunkUtils.readFileContents(ooxmlChunkPath, appContext);
ChunkWrapper chunkWrapper = new ChunkWrapper(chunkFileData, chunkId, totalChunkCount, FileUtils.getMimeTypeForFile(ooxmlFilePathStr));
chunkList.add(chunkWrapper);
...
Reassembler reassembler = new OoxmlReassembler();
byte[] reassembledFileData = reassembler.reassemble(chunkList, annotations, FileUtils.getMimeTypeForFile(firstChunkFilePathStr), totalChunkCount, chunkCompressionPercent);