GDepth:Data PNG Depth Map extractor

gdepth-extract.js

  // A very crude tool to extract GDepth:Data chunks from the XMP data in images
  // that use the Lens Blur feature in Google's Android Camera App
  // Usage: node gdepth-extract.js <image name.jpg>
  // Outputs <image name.png>
  
  // Requires Buffer Tools for buffer.indexOf(): npm install buffertools
  
  require('buffertools').extend();
  var fs = require('fs'),
      image = (process.argv)[2],
      outFilename = image.slice(0,image.lastIndexOf('.')) + '.png',
      data,
      stringMarkers = {
        start: 'GDepth:Data="',
        end: '"'
      },
      findData = function() {
        var xmpBuffer = new Buffer(data.toString('utf8'), 'base64');
            fs.writeFileSync(outFilename, xmpBuffer, {encoding: 'utf8'});
      },
      getFileContents = function() {
        var tempData = fs.readFileSync(image),
            startMarker = tempData.indexOf(stringMarkers.start),
            endMarker = tempData.indexOf(stringMarkers.end,  startMarker + stringMarkers.start.length);
        
        dataBuffer = tempData.slice((startMarker + stringMarkers.start.length), (endMarker));
        
        var bufferLength = dataBuffer.length + 1,
            bufferPos = 0,
            fillBuffer = new Buffer(dataBuffer.length),
            fillBufferPos = 0,
            skipLength = 78; // remove the 78 bytes of binary crud - see: http://lunokhod.org/?p=1486    
        
        while(bufferLength--) {
          if(bufferLength < 1) {
            return;
          } else {
            bufferPos = dataBuffer.length - bufferLength;
          }
          if(dataBuffer[bufferPos] == 255) { // this is very crude
            bufferLength -= skipLength;
          } else {
            fillBuffer.writeUInt8(dataBuffer.readUInt8(bufferPos), fillBufferPos);
            fillBufferPos++;
          }
          
          data = fillBuffer.slice(0, fillBufferPos);
          
        }
      },
      init = function() {
        getFileContents();
        findData();
      };
      
  init();

See: http://googleresearch.blogspot.co.nz/2014/04/lens-blur-in-new-google-camera-app.html