使用Scalr调整数据库中的图像大小

Question

我正在尝试从db调整图像的大小。下面是webservlet，在这里我从数据库中获取blob并尝试使用UtilImage调整它的大小。

Problem：我试图调整大小的图像没有显示在浏览器中，我的控制台也没有列出任何堆栈跟踪。在UtilImage.resize()调用(返回一个新的BufferedImage )之后，imageType从5更改为1。

@WebServlet("/images")
public class BildService extends HttpServlet {
    private static final long serialVersionUID = 1L;

    @EJB
    private LesenService lesenService;

    private Veranstaltung veranstaltung;

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Integer veranstaltungId = Integer.parseInt(request.getParameter("id"));
        veranstaltung = lesenService.getVeranstaltungByVeranstaltungId(veranstaltungId);

        if (veranstaltung == null) {
            response.sendError(HttpServletResponse.SC_NOT_FOUND);
            return;
        }       

        response.setContentType(veranstaltung.getFormat());
        OutputStream os = response.getOutputStream();

        byte[] img = UtilImage.resizeScalr(veranstaltung.getBild(), veranstaltung.getFormat());
        os.write(img);          
    }   
}

This is my UtilImage class:

    public class UtilImage {
    public static final byte[] resizeScalr(byte[] img, String type) {
        if (img != null) {
            BufferedImage bImage = getBufferedImage(img);
            double scaleFactor = getScaleFactor(bImage.getWidth(), UtilKonstanten.PICTURE_WIDTH);
            int targetWidth = (int) (scaleFactor * bImage.getWidth());
            int targetHeight = (int) (scaleFactor * bImage.getHeight());
            // return getByteArray(Scalr.resize(bImage, targetWidth,
            // targetHeight), type);
            return getByteArray(Scalr.resize(bImage, Scalr.Method.BALANCED, targetWidth, targetHeight), type);
        }
        return null;
    }

    private static final double getScaleFactor(int width, int wishwidth) {
        return (double) wishwidth / width;
    }

    private static final BufferedImage getBufferedImage(byte[] array) {
        InputStream is = new ByteArrayInputStream(array);
        BufferedImage img;
        try {
            img = ImageIO.read(is);
            return img;
        } catch (IOException e) {
            // TODO
            e.printStackTrace();
        }
        return null;
    }

    private static final byte[] getByteArray(BufferedImage img, String type) {

        try {
            ByteArrayOutputStream os = new ByteArrayOutputStream();
            ImageIO.write(img, type, os);
            byte[] byteArray = os.toByteArray();
            os.close();
            return byteArray;
        } catch (IOException e) {
            // TODO
            e.printStackTrace();
        }
        return null;
    }
}

非常感谢你的帮助！

Answer 1

不幸的是，我没有贴出这个问题的答案。据我所知，这是某种类型的东西，没有正确保存，因此浏览器无法解析该类型。-> "img“，而不是"application/img”或类似的东西。