Question

我有一个来自this教程的代码。它进入了learning-selenium-easy.blogspot.com网站，在“阅读次数最多/受欢迎的帖子”部分中查找并拍照：

 class SshotofElement {

    public static void screenShotElement() throws InterruptedException,IOException {
        System.setProperty("webdriver.chrome.driver", "chromedriver.exe");

        DesiredCapabilities capabilities = DesiredCapabilities.chrome();
        capabilities.setCapability("marionette", true);
        WebDriver driver = new ChromeDriver(capabilities);

        driver.get("http://learn-selenium-easy.blogspot.com/");
        driver.manage().window().maximize();

        // Xpath of element to take screen shot
        WebElement element=driver.findElement(By.xpath("//*[@id='PopularPosts1']"));
        System.out.println(element.getSize());
        File screenshot = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);

        // Take full screen screenshot
        BufferedImage  fullImg = ImageIO.read(screenshot);
        Point point = element.getLocation();
        int elementWidth = element.getSize().getWidth();
        int elementHeight = element.getSize().getHeight();
        BufferedImage elementScreenshot= fullImg.getSubimage(point.getX(), point.getY(), elementWidth,elementHeight);  //exception here

        // crop the image to required
        ImageIO.write(elementScreenshot, "png", screenshot);
        FileUtils.copyFile(screenshot, new File("mostread_screenshot.png"));//path to save screen shot

        driver.close();
    }
}

我遇到java.awt.image.RasterFormatException: (y + height) is outside of Raster异常，但是在第BufferedImage elementScreenshot= fullImg.getSubimage(point.getX(), point.getY(), elementWidth,elementHeight);行。我不确定为什么会这样，因为图像的点和大小是从元素本身获取的。

Answer 1

您正在裁剪的元素图像在代码拍摄的屏幕快照中不存在。如果您放置调试并打印全屏快照路径并手动查看，则可以看到其中没有从图像中裁剪出所需的元素。
因此，首先我们需要滚动页面，将所需元素带入视图，然后截取屏幕截图。然后我们需要根据元素的位置裁剪图像。
此外，Point类也不十分可靠，无法提供元素的确切位置。

第二，如果我们看到以下值

ImageIO.read(screenshot).getHeight() // ~ 943 => Total height
element.getSize().getHeight() // ~ 511 => Element height 
point.getY() // ~ 743 => start top side y coordinate of element

所以我相信从x，y绘制高度为743的矩形时超出了原始屏幕截图坐标。

所以我们需要在传递坐标的同时进行一些调整。

@Test
public void subImageTest() throws InterruptedException, IOException {
    driver.get("http://learn-selenium-easy.blogspot.com/");
    ((JavascriptExecutor)driver).executeScript("window.scrollBy(0,600)");
   File screenshot = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);

    WebElement element=driver.findElement(By.xpath("//*[@id='PopularPosts1']"));
    System.out.println(element.getSize());

  // Take full screen screenshot
    BufferedImage  fullImg = ImageIO.read(screenshot);
    ImageIO.read(screenshot).getHeight()
    System.out.println(fullImg.getHeight()); 
    System.out.println(fullImg.getWidth());

    Point point = element.getLocation();
    int elementWidth = element.getSize().getWidth(); 
    int elementHeight = element.getSize().getHeight();

    // Now no exception here
    BufferedImage elementScreenshot= fullImg.getSubimage(220, 170,elementWidth+150,elementHeight+100);

    // crop the image to required
    ImageIO.write(elementScreenshot, "png", screenshot);
    FileUtils.copyFile(screenshot, new File("C:\\Users\\AppData\\Local\\Temp\\mostread_screenshot.png"));//path to save screen shot

}

程序执行后元素的最终子图像

Answer 2

RasterFormatException

如果<{3}}中的布局信息无效，则会抛出 Java文档 RasterFormatException。

getLocation（）

根据硒文档 Raster返回包含该元素左上角位置的点。

getSubimage（）

根据 Java文档 getLocation()返回由指定矩形区域定义的子图像。返回的BufferedImage与原始图像共享相同的数据数组，并定义为：

getSubimage
public BufferedImage getSubimage(int x,
                 int y,
                 int w,
                 int h)
Returns a subimage defined by a specified rectangular region. The returned BufferedImage shares the same data array as the original image.

Parameters: 
    x - the X coordinate of the upper-left corner of the specified rectangular region 
    y - the Y coordinate of the upper-left corner of the specified rectangular region 
    w - the width of the specified rectangular region 
    h - the height of the specified rectangular region 

Returns: 
    a BufferedImage that is the subimage of this BufferedImage. 

Throws: 
    RasterFormatException - if the specified area is not contained within this BufferedImage.

我已经编写了自己的代码，并添加了几行System.out.println()以展示到底出了什么问题。

代码块：

public class A_demo 
{
    public static void main(String[] args) throws Exception 
    {
            System.setProperty("webdriver.chrome.driver", "C:\\Utility\\BrowserDrivers\\chromedriver.exe");
            ChromeOptions options = new ChromeOptions();
            options.addArguments("start-maximized");
            options.addArguments("disable-infobars");
            WebDriver driver = new ChromeDriver(options);
            driver.get("http://learn-selenium-easy.blogspot.com/");
            // Xpath of element to take screen shot
            WebElement element=driver.findElement(By.xpath("//*[@id='PopularPosts1']"));
            System.out.println("Element size is:"+element.getSize());
            File screenshot = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);
            FileUtils.copyFile(screenshot, new File("./Screenshots/mostread_TakesScreenshot.png")); //path to save screen shot

            // Take full screen screenshot
            BufferedImage  fullImg = ImageIO.read(screenshot);
            Point point = element.getLocation();
            System.out.println("Co-ordinates where on the page is the top left-hand corner of the rendered element:"+point);
            int elementWidth = element.getSize().getWidth();
            System.out.println("Element width is:"+elementWidth);
            int elementHeight = element.getSize().getHeight();
            System.out.println("Element height is:"+elementHeight);
            BufferedImage elementScreenshot= fullImg.getSubimage(point.getX(), point.getY(), elementWidth,elementHeight);  //exception here

            // crop the image to required
            ImageIO.write(elementScreenshot, "png", screenshot);
            FileUtils.copyFile(screenshot, new File("./Screenshots/mostread_BufferedImage.png"));//path to save screen shot
    }    
}

控制台输出：

INFO: Detected dialect: W3C
Element size is:(340, 486)
Co-ordinates where on the page is the top left-hand corner of the rendered element:(104, 744)
Element width is:340
Element height is:486
Exception in thread "main" java.awt.image.RasterFormatException: (y + height) is outside of Raster
    at sun.awt.image.ByteInterleavedRaster.createWritableChild(Unknown Source)
    at java.awt.image.BufferedImage.getSubimage(Unknown Source)
    at demo.A_demo.main(A_demo.java:78)

说明

如前所述，按照您的代码块fullImg.getSubimage()将尝试返回BufferedImage，即 elementScreenshot ，它将是由矩形区域指定的子图像：

x：指定矩形区域左上角的X坐标-point.getX()- 104
y：指定矩形区域左上角的Y坐标-point.getY()- 744
w：指定矩形区域的宽度-elementWidth- 340
h：指定矩形区域的高度-elementHeight- 486

因此，BufferedImage的预期高度变为744 + 486 = 1230 ，这与光栅。因此，您会看到错误。

解决方案

要使用getSubimage()和selenium截取特定元素或特定div的屏幕截图，可以使用 AShot() 方法导入 ashot- Selenium Java Client v3.14.0 ， ChromeDriver v2.41 ， Chrome v 68.0 时为1.4.4.jar 。 / p>

注意： ashot-1.4.4.jar 中的 AShot() 方法仅在启用java的情况下有效< em> Web应用程序。

代码块：

import ru.yandex.qatools.ashot.AShot;
import ru.yandex.qatools.ashot.Screenshot;

public class A_demo 
{
    public static void main(String[] args) throws Exception 
    {
        System.setProperty("webdriver.chrome.driver", "C:\\Utility\\BrowserDrivers\\chromedriver.exe");
        ChromeOptions options = new ChromeOptions();
        options.addArguments("start-maximized");
        options.addArguments("disable-infobars");
        WebDriver driver = new ChromeDriver(options);
        driver.get("http://learn-selenium-easy.blogspot.com/");
        WebElement myWebElement = new WebDriverWait(driver, 20).until(ExpectedConditions.visibilityOfElementLocated(By.xpath("//div[@id='PopularPosts1']")));
        ((JavascriptExecutor)driver).executeScript("arguments[0].scrollIntoView();", myWebElement);
        Screenshot myScreenshot = new AShot().takeScreenshot(driver, myWebElement);
        ImageIO.write(myScreenshot.getImage(),"PNG",new File("./Screenshots/elementAShotScreenshot.png"));
        driver.quit();
    }    
}

参考

您可以在以下位置找到一些相关的讨论

Outro

您可以在Selenium: Not able to take complete page screenshot using aShot library

中找到有关所有基于 Java 的屏幕截图方法的详细讨论。

Selenium：java.awt.image.RasterFormatException：（y +高度）在使用元素大小和位置时在Raster之外

2 个答案:

RasterFormatException

getLocation（）

getSubimage（）

说明

解决方案

参考

Outro