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我正在尝试捕获此设备扫描的指纹-> http://www.nitgen.com/eng/product/finkey.html

我能够扫描指纹并成功保存二进制数据。我还可以在图片框中显示指纹。但是，当我尝试保存图片框中显示的指纹时，我收到一个错误，即图片框的图像为空。

下面是我捕获指纹并从图片框中保存图像的代码。

public class Form1 : System.Windows.Forms.Form
{
    public NBioBSPCOMLib.NBioBSP objNBioBSP;
    public NBioBSPCOMLib.IExtraction objExtraction;
    private PictureBox pictureExtWnd;

    private void Form1_Load(object sender, System.EventArgs e)
    {
        // Create NBioBSP object
        objNBioBSP = new NBioBSPCOMLib.NBioBSPClass();
        objExtraction = (NBioBSPCOMLib.IExtraction)objNBioBSP.Extraction;
        pictureExtWnd.Image = new Bitmap(pictureExtWnd.Width, pictureExtWnd.Height);
    }

    private void buttonEnroll_Click(object sender, System.EventArgs e)
    {
        //tell NBIO to not display their fingerprint scanning window
        objExtraction.WindowStyle = NBioBSPType.WINDOW_STYLE.INVISIBLE;

        //set the color of the fingerprint captured
        objExtraction.FPForeColor = "000000";

        //set the color of the background where the fingerprint will be displayed
        objExtraction.FPBackColor = "FFFFFF";

        //tell NBIO that the scanned fingerprint will be displayed in the picturebox
        //by giving the handle control to NBIO
        objExtraction.FingerWnd = pictureExtWnd.Handle.ToInt32();

        //start scanning the fingerprint. This is also where the fingerprint
        //is displayed in the picturebox. 
        objExtraction.Capture((int)NBioBSPType.FIR_PURPOSE.VERIFY);

        //if there's no problem while scanning the fingerprint, save the fingerprint image
        if (objExtraction.ErrorCode == NBioBSPError.NONE)
        {
            string fileName = RandomString.GetRandomString(16, true) + ".bmp";

            using (SaveFileDialog sfdlg = new SaveFileDialog())
            {
                sfdlg.Title = "Save Dialog";
                sfdlg.Filter = "Bitmap Images (*.bmp)|*.bmp|All files(*.*)|*.*";
                if (sfdlg.ShowDialog(this) == DialogResult.OK)
                {
                    pictureExtWnd.Image.Save(sfdlg.FileName, ImageFormat.Bmp);
                    MessageBox.Show("FingerPrint Saved Successfully.");
                }
            }
        }
        else
        {
            MessageBox.Show("FingerPrint Saving Failed!");
        }
    }
}

我试过封闭在里面

using(Graphics g = new Graphics)
{
    objExtraction.Capture((int)NBioBSPType.FIR_PURPOSE.VERIFY);
}

因为我已经读过，在对图像进行编辑时，您需要使用图形。但显然没有发生任何事情，因为 api 没有使用我实例化的图形对象。

UPDATE: This is what I ended up doing:

using (SaveFileDialog sfdlg = new SaveFileDialog())
        {
            sfdlg.Title = "Save Dialog";
            sfdlg.Filter = "Bitmap Images (*.bmp)|*.bmp|All files(*.*)|*.*";
            if (sfdlg.ShowDialog(this) == DialogResult.OK)
            {
                Graphics gfx = this.pictureExtWnd.CreateGraphics();
                Bitmap bmp = new Bitmap(this.pictureExtWnd.Width, this.pictureExtWnd.Height);
                this.pictureExtWnd.DrawToBitmap(bmp, new Rectangle(0, 0, this.pictureExtWnd.Width, this.pictureExtWnd.Height));
                bmp.Save(sfdlg.FileName, ImageFormat.Bmp);

                gfx.Dispose();
                //pictureExtWnd.Image.Save(sfdlg.FileName, ImageFormat.Bmp);
                MessageBox.Show("Saved Successfully...");
            }
        }
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1 回答 1

4 
    objExtraction.FingerWnd = pictureExtWnd.Handle.ToInt32();

You passed the window handle to the fingerprint scanner. That's a common way to tell a chunk of native code about a window that it can draw to. It will typically sub-class the window procedure to respond to WM_PAINT requests, for example, same idea as NativeWindow.WndProc().

Implied however is that the Image property is useless. That native code has no idea that this is a PictureBox control and that it has an Image property. It only knows about the native window that was created for the control.

Do look in the api for an option to save the image, this ought to be available. If not then your first shot at saving it is using the picture box' DrawToBitmap() method. Which may work if the scanner implements the WM_PRINT message handler. If that doesn't work then your only other backup plan is to use Graphics.CopyFromScreen(). Which will always work, as long as the window is in the foreground. Similar to using the PrtSc button on your keyboard, a screen-shot.

于 2013-01-06T14:14:44.510 回答