Selenium&EmguCV实现爬虫图片识别

概述

爬虫需要抓取网站价格，与一般抓取网页区别的是抓取内容是通过AJAX加载，并且价格是通过CSS背景图片显示的。

每一个数字对应一个样式，如'p_h57_5'

.p_h57_5 {
background: url('http://pic.c-ctrip.com/priceblur/h57/3713de5c594648529f39d031243966dd.gif') no-repeat -590px;
padding: 0 6px;
font-size: 18px;
}

数字对应的样式和对应的backgroundimg都是动态改变的，需要获取到每一个房型的房价。虽然后来有了其它渠道获取房价，这里记录一下用Selenium&Emgu抓取的方式。
流程：

1.Selenium访问网址
2.全屏截图
3.Selenium选择器获取房型等信息
4.Selenium选择器获取价格DOM元素，计算出价格元素的相对位置，截取价格图片，使用Emgu识别价格并且输出

实现

```C#
static void Main(string[] args)
{

        //访问网址
        ChromeOptions options = new ChromeOptions();
        options.AddArguments("--start-maximized --disable-popup-blocking");
        var driver = new ChromeDriver(options);
        driver.Navigate().GoToUrl("http://hotels.ctrip.com/hotel/992765.html");

   try
        {
            new WebDriverWait(driver, TimeSpan.FromSeconds(1)).Until(
                ExpectedConditions.ElementExists((By.ClassName("htl_room_table")))); //表示已加载完毕
        }
        finally
        {
            
        }
        
        //删除价格的¥符号
        ReadOnlyCollection<IWebElement> elementsList = driver.FindElementsByCssSelector("tr[expand]");
        driver.ExecuteScript(@"
            var arr =  document.getElementsByTagName('dfn');
            for(var i=0;i<arr.length;i++){
                arr[i].style.display = 'none';     
            }
        ");
        
        //全屏截图
        var image2 = GetEntereScreenshot(driver);
        image2.Save(@"Z:\111.jpg");

        //输出
        Console.WriteLine("{0,-20}{1,-20}{2,-20}", "房型", "类型", "房价");
        foreach (IWebElement _ in elementsList)
        {
            //var image = _.Snapshot();
            //image.Save(@"Z:\" + Guid.NewGuid() + ".jpg");
            //var str = ORC_((Bitmap)image);
            var roomType = "";
            try
            {
                roomType = _.FindElement(By.CssSelector(".room_unfold")).Text;

            }
            catch (Exception)
            {
            }
            
            var roomTypeText = regRoomType.Match(roomType);
            
            var roomTypeName = _.FindElement(By.CssSelector("span.room_type_name")).Text;

            //价格元素生成图片
            var image = _.FindElement(By.CssSelector("span.base_price")).SnapshotV2(image2);
            //识别
            var price = ORC_((Bitmap)image);
            Console.WriteLine("{0,-20}{1,-20}{2,-20}", roomTypeText.Value, roomTypeName, price);
        }
        Console.Read();
    }

```

图片识别方法
```C#

static Program()
{
ocr.SetVariable("tesseditchar_whitelist", "0123456789");
}

    private static Tesseract _ocr = new Tesseract(@"C:\Emgu\emgucv-windows-universal-cuda 2.9.0.1922\bin\tessdata", "eng", Tesseract.OcrEngineMode.OEM_TESSERACT_CUBE_COMBINED);
    //传入图片进行识别
    public static string ORC_(Bitmap img)
    {
        //""标示OCR识别调用失败
        string re = "";
        if (img == null)
            return re;
        else
        {


            Bgr drawColor = new Bgr(Color.Blue);
            try
            {
                Image<Bgr, Byte> image = new Image<Bgr, byte>(img);


                using (Image<Gray, byte> gray = image.Convert<Gray, Byte>())
                {
                    _ocr.Recognize(gray);
                    Tesseract.Charactor[] charactors = _ocr.GetCharactors();
                    foreach (Tesseract.Charactor c in charactors)
                    {
                        image.Draw(c.Region, drawColor, 1);
                    }


                    re = _ocr.GetText();


                }
                return re;
            }
            catch (Exception ex)
            {

                return re;
            }
        }
    }

```

Selenium内置了截图方法，只能截取浏览器中显示的内容，找到一个全屏截图的方式（内置截图+控制滚动条,图片拼接）
```C#

public static Bitmap GetEntereScreenshot(IWebDriver _driver)
{

        Bitmap stitchedImage = null;
        try
        {
            long totalwidth1 = (long)((IJavaScriptExecutor)_driver).ExecuteScript("return document.body.offsetWidth");//documentElement.scrollWidth");

            long totalHeight1 = (long)((IJavaScriptExecutor)_driver).ExecuteScript("return  document.body.parentNode.scrollHeight");

            int totalWidth = (int)totalwidth1;
            int totalHeight = (int)totalHeight1;

            // Get the Size of the Viewport
            long viewportWidth1 = (long)((IJavaScriptExecutor)_driver).ExecuteScript("return document.body.clientWidth");//documentElement.scrollWidth");
            long viewportHeight1 = (long)((IJavaScriptExecutor)_driver).ExecuteScript("return window.innerHeight");//documentElement.scrollWidth");

            int viewportWidth = (int)viewportWidth1;
            int viewportHeight = (int)viewportHeight1;


            // Split the Screen in multiple Rectangles
            List<Rectangle> rectangles = new List<Rectangle>();
            // Loop until the Total Height is reached
            for (int i = 0; i < totalHeight; i += viewportHeight)
            {
                int newHeight = viewportHeight;
                // Fix if the Height of the Element is too big
                if (i + viewportHeight > totalHeight)
                {
                    newHeight = totalHeight - i;
                }
                // Loop until the Total Width is reached
                for (int ii = 0; ii < totalWidth; ii += viewportWidth)
                {
                    int newWidth = viewportWidth;
                    // Fix if the Width of the Element is too big
                    if (ii + viewportWidth > totalWidth)
                    {
                        newWidth = totalWidth - ii;
                    }

                    // Create and add the Rectangle
                    Rectangle currRect = new Rectangle(ii, i, newWidth, newHeight);
                    rectangles.Add(currRect);
                }
            }

            // Build the Image
            stitchedImage = new Bitmap(totalWidth, totalHeight);
            // Get all Screenshots and stitch them together
            Rectangle previous = Rectangle.Empty;
            foreach (var rectangle in rectangles)
            {
                // Calculate the Scrolling (if needed)
                if (previous != Rectangle.Empty)
                {
                    int xDiff = rectangle.Right - previous.Right;
                    int yDiff = rectangle.Bottom - previous.Bottom;
                    // Scroll
                    //selenium.RunScript(String.Format("window.scrollBy({0}, {1})", xDiff, yDiff));
                    ((IJavaScriptExecutor)_driver).ExecuteScript(String.Format("window.scrollBy({0}, {1})", xDiff, yDiff));
                    System.Threading.Thread.Sleep(200);
                }

                // Take Screenshot
                var screenshot = ((ITakesScreenshot)_driver).GetScreenshot();

                // Build an Image out of the Screenshot
                Image screenshotImage;
                using (MemoryStream memStream = new MemoryStream(screenshot.AsByteArray))
                {
                    screenshotImage = Image.FromStream(memStream);
                }

                // Calculate the Source Rectangle
                Rectangle sourceRectangle = new Rectangle(viewportWidth - rectangle.Width, viewportHeight - rectangle.Height, rectangle.Width, rectangle.Height);

                // Copy the Image
                using (Graphics g = Graphics.FromImage(stitchedImage))
                {
                    g.DrawImage(screenshotImage, rectangle, sourceRectangle, GraphicsUnit.Pixel);
                }

                // Set the Previous Rectangle
                previous = rectangle;
            }
        }
        catch (Exception ex)
        {
            // handle
        }
        return stitchedImage;
    }

```

最后的是根据传入的元素和全屏截图，获取到价格元素的图片

```C#

public static Image SnapshotV2(this IWebElement element, Bitmap bitmap)
{
Size size = new Size(
Math.Min(element.Size.Width, bitmap.Width),
Math.Min(element.Size.Height, bitmap.Height));
Rectangle crop = new Rectangle(element.Location, size);
return bitmap.Clone(crop, bitmap.PixelFormat);
}

```

运行效果如下