在C#中使用WIA获取扫描仪数据(五、注册事件)
好了,现在我们能在c#里通过编程扫描图像了。还不满足?对,在前面的例子里,需要扫描的时候总是要按下一个扫描按钮,既傻又费事。现在的扫描仪,上面往往会多几个额外的按钮用来和用户交互,例如我是用的HP G2410上就有两个按钮:扫描及复制。那么,能不能用这两个按钮来代替程序里的那个难看的按钮呢?
在WIAAL里,我们可以同过注册设备事件,监听事件等方式和设备上的按钮交互。
注册事件
还记得我们在上节提到的DeviceManager对象吗?MSDN官方文档描述:
The Microsoft Windows Image Acquisition (WIA) Device Manager is an extension of the Still Image (STI) Event Monitor. The WIA Device Manager provides objects, methods, and interfaces for the following:
- Installing devices
- Enumerating devices
- Querying properties of installed devices
- Creating device objects
- Monitoring device events
- Acquiring images
- Registering destination applications.
和传统.Net编程不同,WIA的事件,需要先通过DeviceManager的RegisterEvent的方法注册,才能使用。RegisterEvent定义如下:
void RegisterEvent(string EventID, string DeviceID);
其中,EventID是事件的GUID,DeviceID是扫描仪的GUID。在类EventID里,WIA定义了几种基本的事件类型,从定义上不难理解这些ID的所代表的具体事件:
public const string wiaEventDeviceConnected = "{A28BBADE-64B6-11D2-A231-00C04FA31809}"; public const string wiaEventDeviceDisconnected = "{143E4E83-6497-11D2-A231-00C04FA31809}"; public const string wiaEventItemCreated = "{4C8F4EF5-E14F-11D2-B326-00C04F68CE61}"; public const string wiaEventItemDeleted = "{1D22A559-E14F-11D2-B326-00C04F68CE61}"; public const string wiaEventScanEmailImage = "{C686DCEE-54F2-419E-9A27-2FC7F2E98F9E}"; public const string wiaEventScanFaxImage = "{C00EB793-8C6E-11D2-977A-0000F87A926F}"; public const string wiaEventScanFilmImage = "{9B2B662C-6185-438C-B68B-E39EE25E71CB}"; public const string wiaEventScanImage = "{A6C5A715-8C6E-11D2-977A-0000F87A926F}"; public const string wiaEventScanImage2 = "{FC4767C1-C8B3-48A2-9CFA-2E90CB3D3590}"; public const string wiaEventScanImage3 = "{154E27BE-B617-4653-ACC5-0FD7BD4C65CE}"; public const string wiaEventScanImage4 = "{A65B704A-7F3C-4447-A75D-8A26DFCA1FDF}"; public const string wiaEventScanOCRImage = "{9D095B89-37D6-4877-AFED-62A297DC6DBE}"; public const string wiaEventScanPrintImage = "{B441F425-8C6E-11D2-977A-0000F87A926F}";
例如,我们可以使用以下来吗来注册一个事件,并监听它:
manager.RegisterEvent(EventID.wiaEventScanImage, device.DeviceID); manager.OnEvent += (eventID, deviceID, itemID) => { //………… }
枚举设备事件
如果你向我这般,兴冲冲地在OnEvent里加入扫描处理逻辑,然后按下HP G2410上的扫描按钮,你一定会像我一样,在漫长的等待中渐渐失望:扫描仪根本没有按我所想的那样扫描图片。也就是说,wiaEventScanImage这个事件根本不起作用。
幸好能够通过Device类来枚举设备支持的事件,我写了以下一段代码:
Console.WriteLine("Events:"); foreach (DeviceEvent eve in device.Events) { Console.WriteLine("{0}:{1}:{2}", eve.EventID, eve.Name, eve.Description); }
运行后,发现该扫描仪仅仅支持wiaEventDeviceConnected 和 wiaEventDeviceDisconnected ,以及两个HP自定义的事件:按下扫描按钮、按下拷贝按钮。OOXX!
按下按钮扫描图像
修改manager.RegisterEvent方法,使用HP提供的EventID:
manager.RegisterEvent("{0C5E2143-FD9B-490B-9AD5-7637A403566B}", device.DeviceID);
最终我们可以通过按下扫描仪上的扫描按钮来扫描数据了!:)
manager.OnEvent += (eventID, deviceID, itemID) => { Item item = device.Items[1]; CommonDialogClass cdc = new WIA.CommonDialogClass(); ImageFile imageFile = cdc.ShowTransfer(item, "{B96B3CAB-0728-11D3-9D7B-0000F81EF32E}", true) as ImageFile; if (imageFile != null) { var buffer = imageFile.FileData.get_BinaryData() as byte[]; using (MemoryStream ms = new MemoryStream()) { ms.Write(buffer, 0, buffer.Length); pictureBox1.Image = Image.FromStream(ms); } } };