c# - 使用 WIA 自动进纸器扫描仪扫描第二页失败

Question

我正在尝试使用具有自动进纸器的扫描仪扫描多页。目前我的代码非常简单:

WIA.CommonDialog dialog = new WIA.CommonDialog();
WIA.Device device = dialog.ShowSelectDevice(WIA.WiaDeviceType.ScannerDeviceType);
WIA.Items items = dialog.ShowSelectItems(device);
foreach (WIA.Item item in items)
{
    while (true)
    {
        try
        {
            WIA.ImageFile image = (WIA.ImageFile)dialog.ShowTransfer(item);
            if (image != null && image.FileData != null)
            {
                dynamic binaryData = image.FileData.get_BinaryData();
                if (binaryData is byte[])
                    using (MemoryStream stream = new MemoryStream(binaryData))
                    using (Bitmap bitmap = (Bitmap)Bitmap.FromStream(stream))
                    {
                        bitmap.Save(@"C:\Temp\scan.jpg", ImageFormat.Jpeg);
                    }
            }
        }
        catch (COMException)
        {
            break;
        }
    }
}

我尝试查询 WIA_DPS_DOCUMENT_HANDLING_STATUS 属性以查看馈送器中是否有任何可用页面，但总是返回 1，所以如果我得到 WIA_ERROR_PAPER_EMPTY，我知道文档进纸器是空的。

问题是这段代码只扫描了第一页，当 dialog.ShowTransfer 方法再次被调用时，我得到一个异常和 E_FAIL HResult 并且我可以' 扫描更多页面。奇怪的是，当我在调试器中单步执行这段代码时，一切正常，所有页面都被扫描了。

我尝试通过执行 Marshal.ReleaseComObject(image) 和 image = null 释放图像对象，但这没有帮助。 this question 的建议也没有.是不是我做错了什么导致了这些错误？

编辑:我无法为此找到好的解决方案。当进纸器准备扫描下一页时，扫描仪不断抛出 E_FAIL，这需要几秒钟(它不是一个非常快的扫描仪)。因此，我添加了一个循环以继续尝试 10 秒，这是一个我不喜欢的解决方案，但它似乎有效。

编辑 2:这似乎是打印机的 WIA 驱动程序的问题。我用不同品牌的打印机试过，完全没有这个问题。

Answer 1

我正在做同样的事情，并尝试使用您的代码和本示例中的代码:http://www.codeproject.com/Tips/792316/WIA-Scanner-in-Csharp-Windows-Forms

我在 hp scanjet 5590 上测试了您的代码，即使我在调试器中单步执行代码，它也只能获取一张图像。在第二次调用时，dialog.ShowTransfer 抛出 ArgumentException 并显示消息“值不在预期范围内。”我设法通过重置“图像”和“对话框”对象并设置显式传输格式 ID 使其工作。您的代码还将图像写入同一文件。如果应用于您的代码，这对我有用:

WIA.CommonDialog dialog = new WIA.CommonDialog();
        WIA.Device device = dialog.ShowSelectDevice(WIA.WiaDeviceType.ScannerDeviceType);
        WIA.Items items = dialog.ShowSelectItems(device);
        foreach (WIA.Item item in items)
        {
            while (true)
            {
                WIA.ImageFile image = null;
                try
                {
                    dialog = new WIA.CommonDialog();
                    image = (WIA.ImageFile)dialog.ShowTransfer(item,"{B96B3CAB-0728-11D3-9D7B-0000F81EF32E}", false);
                    if (image != null && image.FileData != null)
                    {
                        dynamic binaryData = image.FileData.get_BinaryData();
                        if (binaryData is byte[])
                            using (MemoryStream stream = new MemoryStream(binaryData))
                            using (Bitmap bitmap = (Bitmap) Bitmap.FromStream(stream))
                            {
                                bitmap.Save(String.Format(@"C:\Temp\scan{0}.jpg", Path.GetRandomFileName()),
                                    ImageFormat.Jpeg);
                            }
                    }
                }
                catch (COMException)
                {
                    break;
                }
                finally
                {
                    if (image != null)
                        Marshal.FinalReleaseComObject(image);
                }
            }
        }

该 CodeProject 示例在我的硬件上也失败了，但同样的修复有帮助。如果上面的代码仍然不适合你试试，用这个替换原来的 Scan 方法:

    public static List<Image> Scan(string scannerId)
    {
        List<Image> images = new List<Image>();

        // select the correct scanner using the provided scannerId parameter
        WIA.DeviceManager manager = new WIA.DeviceManager();
        WIA.Device device = null;
        foreach (WIA.DeviceInfo info in manager.DeviceInfos)
        {
            if (info.DeviceID == scannerId)
            {
                // connect to scanner
                device = info.Connect();
                break;
            }
        }
        // device was not found
        if (device == null)
        {
            // enumerate available devices
            string availableDevices = "";
            foreach (WIA.DeviceInfo info in manager.DeviceInfos)
            {
                availableDevices += info.DeviceID + "\n";
            }

            // show error with available devices
            throw new Exception("The device with provided ID could not be found. Available Devices:\n" + availableDevices);
        }

        WIA.Item item = null;
        WIA.CommonDialog dialog = new WIA.CommonDialog();
        WIA.Items items = dialog.ShowSelectItems(device);
        if (items == null)
            return images;

        item = items[1];

        bool hasMorePages = true;
        while (hasMorePages)
        {
            try
            {
                // scan image
                WIA.ICommonDialog wiaCommonDialog = new WIA.CommonDialog();
                WIA.ImageFile image = (WIA.ImageFile)wiaCommonDialog.ShowTransfer(item, wiaFormatBMP, false);

                // save to temp file
                string fileName = Path.GetTempFileName();
                File.Delete(fileName);
                image.SaveFile(fileName);
                try
                {
                    Marshal.FinalReleaseComObject(image);
                }
                finally
                {
                    image = null;
                }
                // add file to output list
                images.Add(Image.FromFile(fileName));
            }
            finally
            {
                //determine if there are any more pages waiting
                WIA.Property documentHandlingSelect = null;
                WIA.Property documentHandlingStatus = null;
                foreach (WIA.Property prop in device.Properties)
                {
                    if (prop.PropertyID == WIA_PROPERTIES.WIA_DPS_DOCUMENT_HANDLING_SELECT)
                        documentHandlingSelect = prop;
                    if (prop.PropertyID == WIA_PROPERTIES.WIA_DPS_DOCUMENT_HANDLING_STATUS)
                        documentHandlingStatus = prop;
                }
                // assume there are no more pages
                hasMorePages = false;
                // may not exist on flatbed scanner but required for feeder
                if (documentHandlingSelect != null)
                {
                    // check for document feeder
                    if ((Convert.ToUInt32(documentHandlingSelect.get_Value()) & WIA_DPS_DOCUMENT_HANDLING_SELECT.FEEDER) != 0)
                    {
                        hasMorePages = ((Convert.ToUInt32(documentHandlingStatus.get_Value()) & WIA_DPS_DOCUMENT_HANDLING_STATUS.FEED_READY) != 0);
                    }
                }
            }
        }
        return images;
    }

也用这个替换 btn_scan_Click 方法:

    private void btn_scan_Click(object sender, EventArgs e)
    {

        try
        {
            //get list of devices available
            List<string> devices = WIAScanner.GetDevices();
            List<Image> images = null;

            //check if device is not available
            if (devices.Count == 0)
            {
                MessageBox.Show("You do not have any WIA devices.");
                this.Close();
            }
            else
            {
                if (devices.Count == 1)
                {
                    images = WIAScanner.Scan(devices[0]);
                }
                else
                {
                    images = WIAScanner.Scan();
                }
            }
            //get images from scanner
            foreach (Image image in images)
            {
                var path = String.Format(@"C:\Temp\scan{0}_{1}.jpg", DateTime.Now.ToString("yyyy-MM-dd HHmmss"), Path.GetRandomFileName());
                image.Save(path, ImageFormat.Jpeg);
            }
        }
        catch (Exception exc)
        {
            MessageBox.Show(exc.Message);
        }
    }