Question

我正在尝试处理并将一系列图像保存到Google云端存储，并在使用App Engine调整图像大小时遇到严重的图像质量问题。

原始图像始终保存，没有任何质量问题，但使用ImageServiceFactory调整大小时，图像会保存极其像素化。我意识到我应该缓冲输入流，但无法想象这会影响图像质量。

ImageServiceFactory只是垃圾吗？

感谢您的帮助！

以下是代码：

  public static void process(String path) {

    Cover cover = null;
    URL url = UrlBuilder.coverUrl(path);

    try {

      HttpURLConnection connection = (HttpURLConnection)           
      url.openConnection();
      connection.setRequestMethod("HEAD");
      connection.connect();
      String contentType = connection.getContentType();
      FileOutput output = new FileOutput(contentType);
      OutputEncoding encoding = output.encoding;

      // create Image object from InputStream.
      InputStream imgStream = url.openStream();
      byte[] imageBytes = ByteStreams.toByteArray(imgStream);
      Image image = ImagesServiceFactory.makeImage(imageBytes);

      // generated details for image path and file name.
      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
      String dir = sdf.format(book.getRelease());
      String ext = output.extension;

      // save original image
      Image ogImage = resizeImage(image, encoding, image.getHeight(), 100);
      String ogPath = dir + "/" + book.getItemCode() + "." + ext;
      String ogLocation = saveImage(ogPath, ogImage);

      // save md image
      Image mdImage = resizeImage(image, encoding, MD_HEIGHT, 100);
      String mdPath = dir + "/" + book.getItemCode() + "_MD." + ext;
      String mdLocation = saveImage(mdPath, mdImage);

    } catch(IOException e) {
      e.printStackTrace();
    }

  }

  private static Image resizeImage(Image image, OutputEncoding encoding, int height, int quality) {

    // create output settings and set image quality.
    OutputSettings settings = new OutputSettings(encoding);
    settings.setQuality(quality);

    // Get an instance of the imagesService to transform images.
    ImagesService imagesService = ImagesServiceFactory.getImagesService();

    int width = (int) Math.floor(height * image.getWidth() / image.getHeight());

    Transform transform = ImagesServiceFactory.makeResize(width, height, false);
    Image resizedImage = imagesService.applyTransform(transform, image, settings);

    return resizedImage;

  }

  private static String saveImage(String fileName, Image image) {

    byte[] content = image.getImageData();
    Storage storage = StorageOptions.getDefaultInstance().getService();

    // Modify access list to allow all users with link to read file
    List<Acl> acls = new ArrayList<>();
    acls.add(Acl.of(Acl.User.ofAllUsers(), Acl.Role.READER));

    BlobInfo info = BlobInfo.newBuilder(bucket, fileName).setAcl(acls).build();

    // the inputstream is closed by default, so we don't need to close it here
    Blob blob = storage.create(info, content);

    // return the public download link
    return blob.getMediaLink();

  }

  private static class FileOutput {

    public String extension;
    public OutputEncoding encoding;

    public FileOutput(String mimeType) {

      switch(mimeType) {
        case "image/png":
          extension = "png";
          encoding = ImagesService.OutputEncoding.PNG;
          break;
        case "image/jpeg":
        default:
          extension = "jpg";
          encoding = ImagesService.OutputEncoding.JPEG;
          break;
      }

    }

  }

Answer 1

这是一个操作顺序问题。没有代码，我正在保存图像的多个大小（sm，md，lg等）。我正在处理并保存图像从最小到最大。撤销订单已解决了这个问题。

App Engine图像处理（JAVA）的图像质量问题

1 个答案: