code: function extractHOGFromHistograms(histograms, options) {
    var blockSize = options.blockSize || 2;
    var blockStride = options.blockStride || (blockSize / 2);
    var normalize = norms[options.norm || "L2"];
  
    var blocks = [];
    var blocksHigh = histograms.length - blockSize + 1;
    var blocksWide = histograms[0].length - blockSize + 1;
  
    for (var y = 0; y < blocksHigh; y += blockStride) {
      for (var x = 0; x < blocksWide; x += blockStride) {
        var block = getBlock(histograms, x, y, blockSize);
        normalize(block);
        blocks.push(block);
      }
    }
    return Array.prototype.concat.apply([], blocks);
  }
docs: /* This function is decoupled so you can extract histograms for an entire image
  to save recomputation, and use these to get HOGs from individual windows