c# - 通过 Feeder 进行 WIA 扫描

Question

WIA 通过 Feeder 扫描

这是我的设备属性:

Document Handling Select = 1 (2 is for flatbed, and 1 is for the feeder.)

这是我的项目(页面)属性:

Horizontal Resolution = 150
Vertical Resolution = 150
Horizontal Extent = 500 (I want to get it first to work, then I'll play with the extents.),
Vertical Extent = 500
Bits Per Pixel = 8
Current Intent = 4

如果我将“Document Handling Select”设置为“2”，一切都会顺利进行。当我将它设置为“1”并运行它时，就在我说 item.Transfer()(或 item.Transfer(bmp/jpeg/pngGuid))之前，我收到异常“值不在预期范围内”。

这太烦人了，有什么值(value)？我在网上搜索了一下，只找到了一点信息，但帮助不大。

Answer 1

我认为您必须将设备属性“Pages”(ID 3096)从 0 设置为 1 以防止出现异常。我花了一些时间才弄明白这一点。最后，我通过比较调用 CommonDialogClass.ShowSelectItems 前后的设备属性找到了这个属性。

这是一些代码:

    public enum DeviceDocumentHandling : int
    {
        Feeder = 1,
        FlatBed = 2
    }

    const int DEVICE_PROPERTY_DOCUMENT_HANDLING_CAPABILITIES_ID = 3086;
    const int DEVICE_PROPERTY_DOCUMENT_HANDLING_STATUS_ID = 3087;
    const int DEVICE_PROPERTY_DOCUMENT_HANDLING_SELECT_ID = 3088;
    const int DEVICE_PROPERTY_PAGES_ID = 3096;

    public static Property FindProperty(WIA.Properties properties, 
                                        int propertyId)
    {
        foreach (Property property in properties)
            if (property.PropertyID == propertyId)
                return property;
        return null;
    }

    public static void SetDeviceProperty(Device device, int propertyId, 
                                         object value)
    {
        Property property = FindProperty(device.Properties, propertyId);
        if (property != null)
            property.set_Value(value);
    }

    public static object GetDeviceProperty(Device device, int propertyId)
    {
        Property property = FindProperty(device.Properties, propertyId);
        return property != null ? property.get_Value() : null;
    }

    public static void SelectDeviceDocumentHandling(Device device, 
                                DeviceDocumentHandling handling)
    {
        int requested = (int)handling;
        int supported = (int)GetDeviceProperty(device, 
                 DEVICE_PROPERTY_DOCUMENT_HANDLING_CAPABILITIES_ID);
        if ((requested & supported) != 0)
        {
            if ((requested & (int)DeviceDocumentHandling.Feeder) != 0)
                SetDeviceProperty(device, DEVICE_PROPERTY_PAGES_ID, 1);
            SetDeviceProperty(device, 
                   DEVICE_PROPERTY_DOCUMENT_HANDLING_SELECT_ID, requested);
        }
    }