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POhow to read bitmap and meta-data from a png stream/file efficiently?
 

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    <p>I need to decode both bitmap and meta data from PNG input stream using [PNGJ] (http://code.google.com/p/pngj/) library. The problem is that decoding meta data will advance the stream and then I cannot use bitmap = BitmapFactory.decodeStream().</p> <p>Creating Bitmap on my own is OK but if I need to, say, scale bitmap with interpolation I'd rather use BitmapFactory. To use it I have to create a copy of InputStream every time I have to use PNGJ for getting meta data and BitmapFactory for getting a bitmap. It will be nice to return meta data AND Bitmap from a single PNGJ call (at least for most common ARGB_8888 format). </p> <p>In a nutshell, I have to copy the stream to be used by Java libraries which looks like a waste. Returning a bitmap will be one solution.</p> <pre><code> // register an auxilary chunk name PngChunk.factoryRegister(ThumbNailProvider.chunkID, chunkPROP.class); // reader for the stream PngReader pngr = new PngReader(inStream, "debug label PNG reader"); ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); PngWriter pngw = new PngWriter(outputStream, pngr.imgInfo); // copy pre-data chunks pngw.copyChunksFirst(pngr, ChunkCopyBehaviour.COPY_ALL_SAFE); // copy image data for (int row = 0; row &lt; pngr.imgInfo.rows; row++) { ImageLine l1 = pngr.readRow(row); pngw.writeRow(l1, row); } // copy after-data chunks pngw.copyChunksLast(pngr, ChunkCopyBehaviour.COPY_ALL); pngr.end(); // close inStream but not its copy pngw.end(); // close out stream // save a copy of the stream for Java Libraries; data.inputStream = new ByteArrayInputStream(outputStream.toByteArray()); // read the chunk ChunksList chunkList = pngr.getChunksList(); PngChunk chunk = chunkList.getById1(L2ThumbNailProvider.chunkID); if (chunk != null) { ... } </code></pre>
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