GoogleCloudOCR

This one uses Google cloud vision for image text verification. The API key needs to be passed as a parameter for the custom function.
Text in the screenshot image is stored in a string and then the text2match is verified within that string.

import java.io.File;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Base64;

import com.google.gson.JsonArray;
import com.google.gson.JsonObject;
import com.jayway.jsonpath.JsonPath;

import okhttp3.*;
import org.apache.commons.io.FileUtils;
import org.apache.commons.lang3.exception.ExceptionUtils;
import org.openqa.selenium.OutputType;
import org.openqa.selenium.TakesScreenshot;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.remote.RemoteWebDriver;

public class ImageTextVerification extends TestsigmaCustomFunctions {
    private final MediaType JSON
            = MediaType.get("application/json; charset=utf-8");
    private OkHttpClient okHttpClient = new OkHttpClient();
    private StringBuilder stringBuilder = new StringBuilder();

    @CustomTestStep
    public TestStepResult checkJSONContent(String apiKey, String text2match){
        TestStepResult result = new TestStepResult();
        try {
            Response response = getTextFromImageUsingGCVREST(apiKey);
            String responseJSON = response.body().string();
            //System.out.println(responseJSON.length());
            String imageText = JsonPath.parse(responseJSON).read(
                    "$.responses[0].textAnnotations[0].description");
            //stringBuilder.append("ImageText: "+imageText);
            if (imageText.contains(text2match)) {
                 //int matchTextPosition = imageText.indexOf(text2match);
                stringBuilder.append(String.format("Given text '%s' found in the screenshot.", text2match));
                result.setStatus(ResultConstants.SUCCESS);
            }
              else{
                  stringBuilder.append(String.format("Given text '%s' not found in the screenshot.", text2match));
                result.setStatus(ResultConstants.FAILURE);
            }
        }catch (MalformedURLException malformedURLException) {
            stringBuilder.append(ExceptionUtils.getStackTrace(malformedURLException));
            result.setMessage(stringBuilder.toString());
            result.setStatus(ResultConstants.FAILURE);
            result.setMessage("malformedURLException:"+malformedURLException.getMessage());
        } catch (IOException ioException) {
            stringBuilder.append(ExceptionUtils.getStackTrace(ioException));
            result.setMessage(stringBuilder.toString());
            result.setStatus(ResultConstants.FAILURE);
            result.setMessage("ioException:"+ioException.getMessage());
        } catch (Exception exception){
            stringBuilder.append(ExceptionUtils.getStackTrace(exception));
            result.setMessage(stringBuilder.toString());
            result.setStatus(ResultConstants.FAILURE);
            result.setMessage("exception:"+exception.getMessage());
        }
        result.setMessage(stringBuilder.toString());
        return result;
    }

    public RequestBody generateRESTRequestBody() throws IOException {
        String jsonString = "{\"requests\": [{\"features\": [{\"type\": \"TEXT_DETECTION\",\"maxResults\": 1}],\"image\": {\"content\": \""+getScreenshotAsB64(getScreenShot())+"\"}}]}";
        return RequestBody.create(JSON,jsonString);
    }

    public Response getTextFromImageUsingGCVREST(String apiKey) throws IOException {
        Request postRequest = new Request.Builder()
                .url("https://vision.googleapis.com/v1/images:annotate?key="+apiKey)
                .post(generateRESTRequestBody())
                .build();
        Response response = okHttpClient.newCall(postRequest).execute();
        return response;
    }

    public String getScreenshotAsB64(File screenshot) throws IOException {
        byte[] fileContent = FileUtils.readFileToByteArray(screenshot);
        return Base64.getEncoder().encodeToString(fileContent);
    }

    public File getScreenShot() throws IOException {
        File screenshotFile = File.createTempFile("TSScreenshot_",".png");
        FileUtils.copyFile(((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE), screenshotFile);
        //stringBuilder.append("\nScreenshot copied to "+screenshotFile.getAbsolutePath());
        //stringBuilder.append("==============");
        return screenshotFile;
    }
}