@Override
public void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException
{
    // Extract parameters
    int width = Integer.parseInt(req.getParameter("width")) - 1;
    int height = Integer.parseInt(req.getParameter("height"));
    String bgColorStr = req.getParameter("bgcolor");
    int bgColor = (bgColorStr == null || bgColorStr.length() == 0) ? 0xffffff : Integer.parseInt(bgColorStr, 16);
    String data = req.getParameter("data");
   
    // Build the bitmap image
    BufferedImage image = buildBitmap(width, height, bgColor, data);
   
    // Compress the image as a JPEG
    ImageWriter writer = ImageIO.getImageWritersByFormatName("jpg").next();
    ImageWriteParam writerParam = writer.getDefaultWriteParam();
    writerParam.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
    writerParam.setCompressionQuality(0.95f);

    // Stream the image to the user agent
    resp.addHeader("Content-Disposition", "attachment; filename=\"FusionCharts.jpg\"");
    resp.setContentType("image/jpeg");
    ImageOutputStream imageOut = ImageIO.createImageOutputStream(resp.getOutputStream());
    writer.setOutput(imageOut);
    writer.write(null, new IIOImage(image, null, null), writerParam);
    imageOut.flush();
    imageOut.close();
}
   
private BufferedImage buildBitmap(int width, int height, int bgColor, String data)
{
    BufferedImage chart = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

    String[] rows = data.split(";");
    int colIdx = 0;
    for (int rowIdx = 0; rowIdx < rows.length; rowIdx++)
    {
        // Split individual pixels
        String[] pixels = rows[rowIdx].split(",");
        colIdx = 0;
        for (int pixelIdx = 0; pixelIdx < pixels.length; pixelIdx++)
        {               
            // Split the color and repeat factor
            String[] clrs = pixels[pixelIdx].split("_");  
            int color = ("".equals(clrs[0])) ? bgColor : Integer.parseInt(clrs[0], 16);
            int repeatFactor = Integer.parseInt(clrs[1]);
           
            // Set the color the specified number of times
            for (int repeatCount = 0; repeatCount < repeatFactor; repeatCount++, colIdx++)
            {                      
                chart.setRGB(colIdx, rowIdx, color);
            }
        }
    }
   
    return chart;
}