I tried using Google Cloud Vision API in Java


・ Gradle project ・ Registered GCP account (For account registration, API usage, and authentication key issuance, refer to here)

Add library

The fastest way to add a gradle library is to look it up in the Maven Repository (https://mvnrepository.com/).

compile group: 'com.google.cloud', name: 'google-cloud-vision', version: '1.100.9'

Credential settings

Authentication information is required when using the GCP API. Create credentials from the GCP console and download the JSON file

Put the downloaded JSON file in the project, execution configuration environmentadd (new) Variables are GOOGLE_APPLICATION_CREDENTIALS The value is the absolute path of the Json file.json

Executing sample code

URL of google official sample


void main() {
        try {
            //Specify the read image
            String inputImgPath = "Absolute path.png ";

            //Extract the analysis result as a text file
            //result.Make txt
            PrintStream outputResultPath = new PrintStream(new FileOutputStream("Absolute path/result.txt"), true);

            detectText(inputImgPath, outputResultPath);
        }catch (FileNotFoundException e) {
        catch (Exception e) {
    //Quoted from sample code
    public static void detectText(String filePath, PrintStream out) throws Exception, IOException {
          List<AnnotateImageRequest> requests = new ArrayList<>();

          ByteString imgBytes = ByteString.readFrom(new FileInputStream(filePath));

          Image img = Image.newBuilder().setContent(imgBytes).build();
          Feature feat = Feature.newBuilder().setType(Type.TEXT_DETECTION).build();
          AnnotateImageRequest request =

          try (ImageAnnotatorClient client = ImageAnnotatorClient.create()) {
            BatchAnnotateImagesResponse response = client.batchAnnotateImages(requests);
            List<AnnotateImageResponse> responses = response.getResponsesList();

            for (AnnotateImageResponse res : responses) {
              if (res.hasError()) {
                out.printf("Error: %s\n", res.getError().getMessage());

              // For full list of available annotations, see http://g.co/cloud/vision/docs
              for (EntityAnnotation annotation : res.getTextAnnotationsList()) {
                //Output text
                out.printf("Text: %s\n", annotation.getDescription());
                //Output coordinates (delete the sentence below if you don't need it)
                out.printf("Position : %s\n", annotation.getBoundingPoly());

I tried to extract the character string in the image below. 文字列.jpg

This is the extraction result.

Text:All thoughts
"Felt pen]
Paid version:Second-level writing(6,700 characters or more)Recording
Free version:Educational writing(1,006 characters) +a..?4 green
Created based on the handwritten female characters of the first grade of elementary school
Original Kanji Morimori Japanese font.

The recorded characters were not read correctly. However, it is very accurate to read this font.

If you put out the coordinates of the characters, it will come out like this.

Position : vertices {
  x: 33
  y: 53
vertices {
  x: 451
  y: 53
vertices {
  x: 451
  y: 310
vertices {
  x: 33
  y: 310

Position : vertices {
  x: 76
  y: 58
vertices {
  x: 125
  y: 58
vertices {
  x: 125
  y: 101
vertices {
  x: 76
  y: 101
Omitted below

This time I wrote it for gradle users. The source code is difficult to understand, but try copying and using it first.

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