code: public VisualizerBuilder setBytesPerPixel(int bytes, long fileLength) {
  		Preconditions.checkArgument(bytes > 0);
  		double nrOfPixels = fileLength / (double) bytes;
  		double pixelsPerRow = Math.floor(settings.fileWidth
  				/ (double) settings.pixelSize);
  		double pixelsPerCol = Math.ceil(nrOfPixels / (double) pixelsPerRow);
  		settings.height = (int) Math.ceil(pixelsPerCol * settings.pixelSize);
  		return this;
  	}
docs: TODO maybe calculate with filelength in visualizer