I trying to attach a screenshot to the index.html or emailable_report.html if a test failed. I found a workable solution, but I would like to disassemble it into smaller parts so that I can use it elsewhere.
However, when I disassemble it into small parts, although it takes the picture, it does not attach it to the report.

This one works for me perfectly:

public static void insertScreenshotToReportByTestResult2(WebDriver driver, ITestResult result){
        if(result.getStatus() == ITestResult.FAILURE) {
            Reporter.setCurrentTestResult(result);
            String date = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
            String screenshotName = result.getTestClass().getRealClass().getSimpleName() + "_" +
                    result.getName() + "_" + new SimpleDateFormat("HHmmss").format(new Date(result.getStartMillis()));
            TakesScreenshot ts = (TakesScreenshot) driver;
            File source = ts.getScreenshotAs(OutputType.FILE);
            try {
                FileUtils.copyFile(source, new File("target/screenshots/" + date + "/" + screenshotName + ".png"));
                String embedImageBase64 = Base64.getEncoder().encodeToString(FileUtils.readFileToByteArray(source));
                Reporter.log("<img alt='Test execution failed' src='data:image/png;base64," + embedImageBase64 + "' width='1280' height='720'/>");
            } catch (IOException e) {
                throw new RuntimeException("Failed to create screenshot and embed into report of failed execution.", e);
            }
        }

This is the disassembled version that does not work perfectly:

public static void insertScreenshotToReportByTestResult(WebDriver driver, ITestResult result){
        if (result.getStatus() == ITestResult.FAILURE){
            attachScreenshotToReport(takeScreenshot(driver, result.getMethod().getMethodName()));
        }
    }

public static File takeScreenshot(WebDriver driver, String testName){
        String date = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String screenshotName = testName + "_" + date;
        TakesScreenshot ts = (TakesScreenshot) driver;
        File source = ts.getScreenshotAs(OutputType.FILE);
        try {
            FileUtils.copyFile(source, new File("target/screenshots/" + date + "/" + screenshotName + ".png"));
        } catch (IOException e) {
            throw new RuntimeException("Failed to create screenshot or failed save to target/screenshots.", e);
        }
        return source;
    }


public static void attachScreenshotToReport(File source){
        try {
            String embedImageBase64 = Base64.getEncoder().encodeToString(FileUtils.readFileToByteArray(source));
            Reporter.log("<img alt='Test execution failed' src='data:image/png;base64," + embedImageBase64 + "' width='1280' height='720'/>");
        } catch (IOException e) {
            throw new RuntimeException("Failed to attach screenshot to the report ", e);
        }
    }