public BlockingReport blkCalculation() throws IOException {
      BlockingReport blockingReport = new BlockingReport();
      BlockingExtractor blockingExtractor;
      blockingExtractor = new BlockingExtractor(sourceFile);
      ImageIO.write(blockingExtractor.displaySurface, "png", outputFile);
      ByteArrayOutputStream blockbytes = new ByteArrayOutputStream();
      ImageIO.write(blockingExtractor.displaySurface, "png", blockbytes);

      blockingReport.map = outputFile.getCanonicalPath();
      blockingReport.maxValue = blockingExtractor.blkmax;
      blockingReport.minValue = blockingExtractor.blkmin;
      blockingReport.completed = true;
      return blockingReport;
    }