Question

这是我为生成PDF而运行的代码

public string ScreenshotFullLength(string Url) {
    UrlScreenshot Shot = new UrlScreenshot(Url, 975, 100);

    int maxHeight = 1250;
    // If you do skip the crop function you 'll get the
    // full lenght of the page. We'll scale it to match
    // a 400 pixel width
    //int newHeight = (Shot.Bitmap.Width / 400) * Shot.Bitmap.Height;
    //Shot.Resize(400, newHeight);

    string Filename = LazyAssFilename();
    string path = Server.MapPath("~") + "/tmp/" + Filename;
    Shot.Bitmap.Save(path, ImageFormat.Png);

    string pdfURL = "";

    Document document = new Document();

    try {

        // step 2:
        // we create a writer that listens to the document
        // and directs a PDF-stream to a file
        pdfURL = Server.MapPath("~") + "\\tmp\\Attest_" + EOFName + ".pdf";
        PdfWriter.GetInstance(document, new FileStream(pdfURL, FileMode.Create));

        // step 3: we open the document
        document.Open();

        // step 4: we add content
        iTextSharp.text.Image jpg = iTextSharp.text.Image.GetInstance(path);


        if (jpg.Height > maxHeight) {
            //we moeten er meer dan 1 maken en croppen
            int loops = (int)(jpg.Height / maxHeight);
            int rest = (int)(jpg.Height % maxHeight);
            int i;
            for (i = 0; i < loops; i++) {
                Bitmap bmpImage = new Bitmap(path);
                Bitmap bmpCrop = bmpImage.Clone(new System.Drawing.Rectangle(0, i * maxHeight, 975, maxHeight),
                bmpImage.PixelFormat);

                iTextSharp.text.Image crpd = iTextSharp.text.Image.GetInstance(bmpCrop, ImageFormat.Png);
                crpd.Alignment = iTextSharp.text.Image.MIDDLE_ALIGN;
                crpd.ScalePercent(60);
                document.Add(crpd);
            }

            //the rest
            Bitmap bmpImage2 = new Bitmap(path);
            Bitmap bmpCrop2 = bmpImage2.Clone(new System.Drawing.Rectangle(0, i * maxHeight, 975, rest),
            bmpImage2.PixelFormat);

            iTextSharp.text.Image crpdRest = iTextSharp.text.Image.GetInstance(bmpCrop2, ImageFormat.Png);
            crpdRest.Alignment = iTextSharp.text.Image.MIDDLE_ALIGN;
            crpdRest.ScalePercent(60);
            document.Add(crpdRest);

        } else {
            jpg.Alignment = iTextSharp.text.Image.MIDDLE_ALIGN;
            jpg.ScalePercent(60);
            document.Add(jpg);
        }

    } catch (DocumentException de) {
        Console.Error.WriteLine(de.Message);
    } catch (IOException ioe) {
        Console.Error.WriteLine(ioe.Message);
    }

    // step 5: we close the document
    document.Close();

    try {
        //screenshots deleten
        File.Delete(path);
    } catch { }

    return pdfURL;
}

这在网站上运行，以制作网页的PDF。但是，当多个人从网站访问此代码时，为了生成他们的PDF，我收到错误：Object is currently in use elsewhere.

STACKTRACE：在System.Drawing.Image.Save（String filename，ImageCodecInfo encoder，EncoderParameters encoderParams）at ...

我该如何解决这个问题？该错误在Shot.Bitmap.Save(path, ImageFormat.Png);

处抛出

Answer 1

刚发现这个类似的question。其中一个答案表明GDI +不是线程安全的，在这种情况下你需要锁定你的Save（）和其他一些方法。

只是为了确认，阅读Image类的信息，尽管这对于单个实例或同一类的不同实例是否含糊不清。

此类型的任何公共静态（在Visual Basic中为Shared）成员都是线程安全。任何实例成员都不能保证是线程安全

Answer 2

我遇到了同样的问题，我有一个工作线程将GUI抽出到其图形界面，但它只在某些时候抛出此异常。用Invoke包装它修复它。

_parent.Invoke( new Action(() => eg.Graphics.DrawImage( _icon, rc )));

当前在其他地方使用的对象（System.Drawing）

2 个答案: