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文档扫描与图像处理

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Java调用文档扫描仪
2024年1月30日

Dynamic Web TWAIN是一个给Web应用添加文档扫描功能的SDK。它会在本地运行一个叫Dynamsoft Service的后端服务，通过TWAIN、WIA、eSCL、SANE和ICA等协议与扫描仪进行通信。该服务是跨平台的，可以在Windows、macOS和Linux上运行。

从Dynamic Web TWAIN v18.4开始，可以通过REST API访问Dynamsoft Service，以便我们可以用不同的编程语言创建文档扫描应用程序。

在本文中，我们将讨论如何使用Java通过这一REST API调用文档扫描仪。使用JavaFX构建了一个桌面应用程序。

使用Dynamsoft Service的REST API在Java中进行文档扫描的一些优点：

  1. 它是跨平台的，支持多种扫描协议。
  2. 如果我们直接调用TWAIN API ，我们需要使用32位的JRE，因为大多数驱动程序都是32位。使用REST API就没有此问题。

准备工作

  • 需要申请一个Dynamic Web TWAIN的许可证来使用它。可以在这里申请。
  • 需要在设备上安装Dynamsoft Service。可以在下表中找到下载链接：
平台 下载链接
Windows Dynamsoft-Service-Setup.msi
macOS Dynamsoft-Service-Setup.pkg
Linux Dynamsoft-Service-Setup.deb
Dynamsoft-Service-Setup-arm64.deb
Dynamsoft-Service-Setup-mips64el.deb
Dynamsoft-Service-Setup.rpm

REST API概览

端点：http://127.0.0.1:18622。可以访问配置页面http://127.0.0.1:18625/对IP等内容进行配置。如果设置了局域网IP，那局域网内其它设备也可以通过安装了Dynamsoft Service的这台设备来扫描文档。不设的话则默认只开放给本机。

API接口：

  1. 列出扫描仪。

    HTTP方法和URL： GET /DWTAPI/Scanners

    响应示例：

    [
  {
    "name":"scanner name",
    "device":"detailed info of the scanner",
    "type": 16
  }
]

    以下是扫描仪类型及其相应值的列表。

    16: TWAIN
32: WIA
64: TWAINX64
128: ICA
256: SANE
512: eSCL
1024: WIFIDIRECT
2048: WIATWAIN

  2. 创建文档扫描作业。

    HTTP方法和URL： POST /DWTAPI/ScanJobs

    请求示例：

    {
  "license":"license of Dynamic Web TWAIN",
  "device":"detailed info of the scanner", #optional. Use the latest device by default
  "config":{ # Device configuration https://www.dynamsoft.com/web-twain/docs/info/api/Interfaces.html#DeviceConfiguration (optional)
    "IfShowUI":true, # show the UI of the scanner
    "Resolution":200,
    "IfFeederEnabled":false, # enable auto document feeder
    "IfDuplexEnabled":false # enable duplex document scanning
  },
  "caps":{ # Capabilities https://www.dynamsoft.com/web-twain/docs/info/api/Interfaces.html#capabilities (optional)
    "exception":"ignore",
    "capabilities":[
      {
        "capability":"", #pixel type
        "curValue":0 #0: black&white, 1: gray, 2: color
      }
    ]
  }
}

    响应：

    状态码201，返回作业ID

  3. 获取扫描的文档图像。

    HTTP方法和URL： GET /DWTAPI/ScanJobs/:jobid/NextDocument

    响应：

    状态码200，返回图像的字节

  4. 获取扫描作业的信息。

    HTTP方法和URL： GET /DWTAPI/ScanJobs/:jobid/DocumentInfo

  5. 删除扫描作业。

    HTTP方法和URL： DELETE /DWTAPI/ScanJobs/:jobid

新建JavaFX项目

使用IntelliJ IDEA创建新的JavaFX项目。

新项目

添加依赖项

在pom.xml中添加OKHttp作为HTTP库。OKHttp适用于桌面和安卓平台。

<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>4.11.0</version>
</dependency>

在pom.xml中添加Jackson作为JSON库。

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-core</artifactId>
    <version>2.15.2</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.15.2</version>
</dependency>

此外，添加PDFBox以将扫描的文档保存为PDF文件。

<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>3.0.0</version>
</dependency>

创建表示数据的类

  1. 扫描设备类Scanner。

    public class Scanner {
    public String name;
    public int type;
    public String device;
    public Scanner(String name, int type, String device){
        this.name = name;
        this.type = type;
        this.device = device;
    }
}

  2. 设备类型常量。

    public class DeviceType {
    public static final int TWAIN = 16;
    public static final int WIA = 32;
    public static final int TWAINX64 = 64;
    public static final int ICA = 128;
    public static final int SANE = 256;
    public static final int ESCL = 512;
    public static final int WIFIDIRECT = 1024;
    public static final int WIATWAIN = 2048;
    public  static String getDisplayName(int type) throws Exception {
      if (type == TWAIN) {
          return "TWAIN";
      }else if (type == WIA) {
          return "WIA";
      }else if (type == TWAINX64) {
          return "TWAINX64";
      }else if (type == ICA) {
          return "ICA";
      }else if (type == SANE) {
          return "SANE";
      }else if (type == ESCL) {
          return "ESCL";
      }else if (type == WIFIDIRECT) {
          return "WIFIDIRECT";
      }else if (type == WIATWAIN) {
          return "WIATWAIN";
      }else{
          throw new Exception("Invalid type");
      }
    }
}

  3. 设备配置。

    public class DeviceConfiguration {
    public boolean IfShowUI = false;
    public int Resolution = 200;
    public boolean IfFeederEnabled = false;
    public boolean IfDuplexEnabled = false;
}

  4. 扫描功能的设置。

    public class CapabilitySetup {
    public int capability;
    public Object curValue;
    public String exception = "ignore";
}

  5. 扫描功能。

    public class Capabilities {
    public String exception = "";
    public List<CapabilitySetup> capabilities = new ArrayList<CapabilitySetup>();
}

Dynamsoft Service类

创建一个新的Dynamsoft Service类，用于调用REST API。

  1. 创建一个类，基本内容如下。

    public class DynamsoftService {
    private String endPoint = "http://127.0.0.1:18622";
    private String license = "";
    public DynamsoftService(){

    }
    public DynamsoftService(String endPoint, String license){
        this.endPoint = endPoint;
        this.license = license;
    }
}

  2. 添加getScanners方法以获取扫描仪列表。

    public List<Scanner> getScanners() throws IOException, InterruptedException {
    OkHttpClient client = new OkHttpClient();
    Request request = new Request.Builder()
            .url(endPoint+"/DWTAPI/Scanners")
            .build();
    try (Response response = client.newCall(request).execute()) {
        String body = response.body().string();
        List<Scanner> scanners = new ArrayList<Scanner>();
        ObjectMapper objectMapper = new ObjectMapper();
        List<Map<String,Object>> parsed = objectMapper.readValue(body,new TypeReference<List<Map<String,Object>>>() {});

        for (Map<String,Object> item:parsed) {
            int type = (int) item.get("type");
            String name = (String) item.get("name");
            String device = (String) item.get("device");
            Scanner scanner = new Scanner(name,type,device);
            scanners.add(scanner);
        }
        return scanners;
    }
}

  3. 添加createScanJob方法，以创建扫描作业。

    public String createScanJob(Scanner scanner) throws Exception {
    return createScanJob(scanner,null,null);
}

public String createScanJob(Scanner scanner,DeviceConfiguration config,Capabilities capabilities) throws Exception {
    Map<String,Object> body = new HashMap<String,Object>();
    body.put("license",this.license);
    body.put("device",scanner.device);
    if (config != null) {
        body.put("config",config);
    }
    if (capabilities != null) {
        body.put("caps",capabilities);
    }
    ObjectMapper objectMapper = new ObjectMapper();
    String jsonBody = objectMapper.writeValueAsString(body);

    OkHttpClient client = new OkHttpClient.Builder()
            .connectTimeout(120, TimeUnit.SECONDS)
            .build();
    RequestBody requestBody = RequestBody.create(jsonBody, JSON);
    Request request = new Request.Builder()
            .url(endPoint+"/DWTAPI/ScanJobs?timeout=120")
            .post(requestBody)
            .build();
    try (Response response = client.newCall(request).execute()) {
        if (response.code() == 201) {
            return response.body().string();
        }else{
            throw new Exception(response.body().string());
        }
    }
}

  4. 添加一个nextDocument方法来获取文档图像。

    public byte[] nextDocument(String jobID) throws Exception {
    return getImage(jobID);
}

private byte[] getImage(String jobID) throws Exception {
    OkHttpClient client = new OkHttpClient.Builder()
            .connectTimeout(120, TimeUnit.SECONDS)
            .build();
    Request request = new Request.Builder()
            .url(endPoint+"/DWTAPI/ScanJobs/"+jobID+"/NextDocument?timeout=120")
            .build();
    String body = "";
    try (Response response = client.newCall(request).execute()) {
        if (response.code() == 200) {
            return response.body().bytes();
        }else{
            return null;
        }
    }
}

给应用添加扫描功能

接下来，我们可以更新primary stage，给它添加扫描功能。

首先，我们可以使用SceneBuilder用FXML设计布局。左侧是用于配置扫描的控件，右侧是用于显示扫描图像的ListView。

界面设计

然后，在控制器中实现相关事件和初始化。

  1. 在初始化过程中，在组合框中加载扫描仪、分辨率和像素类型的列表。

    public void initialize(){
    this.loadResolutions();
    this.loadPixelTypes();
    this.loadScanners();
}

private void loadResolutions(){
    List<Integer> resolutions = new ArrayList<Integer>();
    resolutions.add(100);
    resolutions.add(200);
    resolutions.add(300);
    resolutionComboBox.setItems(FXCollections.observableList(resolutions));
    resolutionComboBox.getSelectionModel().select(1);
}

private void loadPixelTypes(){
    List<String> pixelTypes = new ArrayList<String>();
    pixelTypes.add("Black & White");
    pixelTypes.add("Gray");
    pixelTypes.add("Color");
    pixelTypeComboBox.setItems(FXCollections.observableList(pixelTypes));
    pixelTypeComboBox.getSelectionModel().select(0);
}

private void loadScanners() throws IOException, InterruptedException {
    scanners = service.getScanners();
    List<String> names = new ArrayList<String>();
    for (Scanner scanner:scanners) {
        try {
            names.add(scanner.name + " (" +DeviceType.getDisplayName(scanner.type)+ ")");
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
    scannersComboBox.setItems(FXCollections.observableList(names));
    if (names.size()>0) {
        scannersComboBox.getSelectionModel().select(0);
    }
}

  2. 为ListView的单元格定义DocumentImage类。ListView的单元格包含一个ImageView。

    public class DocumentImage {
    public ImageView imageView;
    public byte[] image;
    public DocumentImage(ImageView imageView,byte[] image) {
        this.imageView = imageView;
        this.image = image;
    }
}

  3. 更新ListView的单元格工厂，使其显示ImageView。

    documentListView.setCellFactory(param -> new ListCell<DocumentImage>() {
    {
        prefWidthProperty().bind(documentListView.widthProperty().subtract(30));
        setMaxWidth(Control.USE_PREF_SIZE);
    }
    @Override
    protected void updateItem(DocumentImage item, boolean empty) {
        super.updateItem(item, empty);

        if (empty) {
            setGraphic(null);
        } else {
            item.imageView.setFitWidth(documentListView.widthProperty().subtract(30).doubleValue());
            setGraphic(item.imageView);
        }
    }
});

  4. 单击扫描按钮后扫描文档。图像将显示在ListView中。

    @FXML
protected void onScanButtonClicked() {
    int selectedIndex = scannersComboBox.getSelectionModel().getSelectedIndex();
    if (selectedIndex != -1) {
        progressStage.show();
        Thread t = new Thread(() -> {
            Scanner scanner  = scanners.get(selectedIndex);
            try {
                DeviceConfiguration config = new DeviceConfiguration();
                config.IfShowUI = showUICheckBox.isSelected();
                config.IfDuplexEnabled = duplexCheckBox.isSelected();
                config.IfFeederEnabled = ADFCheckBox.isSelected();
                config.Resolution = (int) resolutionComboBox.getSelectionModel().getSelectedItem();
                Capabilities caps = new Capabilities();
                caps.exception = "ignore";
                caps.capabilities = new ArrayList<CapabilitySetup>();
                CapabilitySetup pixelTypeSetup = new CapabilitySetup();
                pixelTypeSetup.capability = 257;
                pixelTypeSetup.curValue = pixelTypeComboBox.getSelectionModel().getSelectedIndex();
                caps.capabilities.add(pixelTypeSetup);
                String jobID = service.createScanJob(scanner,config,caps);
                System.out.println("ID: "+jobID);
                byte[] image = service.nextDocument(jobID);
                while (image != null){
                    loadImage(image);
                    image = service.nextDocument(jobID);
                }
            } catch (Exception e) {
                System.out.println(e.getMessage());
            }
            Platform.runLater(() -> {
                progressStage.close();
            });
        });
        t.start();
    }
}

private void loadImage(byte[] image){
    Image img = new Image(new ByteArrayInputStream(image));
    ImageView iv = new ImageView();
    iv.setPreserveRatio(true);
    iv.setImage(img);
    DocumentImage di = new DocumentImage(iv,image);
    documentListView.getItems().add(di);
}

  5. 监听ListView宽度的变化。当宽度更改时，更新ImageView的大小。

    ChangeListener<Number> changeListener = new ChangeListener<Number>() {
    @Override
    public void changed(ObservableValue<? extends Number> observable, Number oldValue, Number newValue) {
        for (DocumentImage item:documentListView.getItems()) {
            item.imageView.setFitWidth(documentListView.widthProperty().subtract(30).doubleValue());
        }
    }
};
documentListView.widthProperty().addListener(changeListener);

  6. 为ListView添加用于删除所选文档图像的右键菜单。

    ContextMenu contextMenu = new ContextMenu();
MenuItem deleteMenuItem = new MenuItem("Delete selected");
deleteMenuItem.setOnAction(e -> {
    var indices = documentListView.getSelectionModel().getSelectedIndices();
    for (int i = indices.size() - 1; i >= 0; i--) {
        int index = indices.get(i);
        documentListView.getItems().remove(index);
    }
});
contextMenu.getItems().add(deleteMenuItem);

  7. 使用PDFBox将扫描的文档保存为PDF文件。

    @FXML
protected void onSaveButtonClicked() throws IOException {
    FileChooser fileChooser = new FileChooser();
    fileChooser.setTitle("Open Resource File");
    File fileToSave = fileChooser.showSaveDialog(null);
    if (fileToSave != null) {
        PDDocument document = new PDDocument();
        int index = 0;
        for (DocumentImage di: documentListView.getItems()) {
            index = index + 1;
            ImageView imageView = di.imageView;
            PDRectangle rect = new PDRectangle((float) imageView.getImage().getWidth(),(float) imageView.getImage().getHeight());
            System.out.println(rect);
            PDPage page = new PDPage(rect);
            document.addPage(page);
            PDPageContentStream contentStream = new PDPageContentStream(document, page);
            PDImageXObject image
                    = PDImageXObject.createFromByteArray(document,di.image,String.valueOf(index));
            contentStream.drawImage(image, 0, 0);
            contentStream.close();
        }
        document.save(fileToSave.getAbsolutePath());
        document.close();
    }
}

好了，我们现在已经完成了demo应用程序的编写。

源代码

欢迎下载源代码并尝试使用：

https://github.com/tony-xlh/JavaFX-Document-Scanner

可以使用Jitpack将封装好的类集成到自己的项目中：https://jitpack.io/#tony-xlh/docscan4j

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