使用iTextSharp替换PDF便签为图片的位置偏移、旋转问题问询

核心逻辑说明 #

你遇到的冲突源于PDF页面旋转属性和注释坐标、内容绘制坐标系的不匹配：设置stamper.RotateContents = false可以让注释原始坐标直接对齐，但插入的内容会继承页面旋转属性。我们只需要手动给图片添加反向旋转抵消页面旋转，同时根据旋转角度调整坐标即可。

修改步骤 #

1. 初始化PdfStamper后保留stamper.RotateContents = false配置
2. 遍历每页时获取页面旋转角度、页面宽高参数
3. 插入图片时根据页面旋转角度，调整图片旋转角度和绘制坐标

完整修改代码 #

修改LoadData方法 #

public void LoadData()
{
    Stream inputPdfStream = new FileStream(txtFilePDF.Text, FileMode.Open, FileAccess.Read, FileShare.Read);
    Stream outputPdfStream = new FileStream("result.pdf", FileMode.Create, FileAccess.Write, FileShare.None);

    reader = new PdfReader(inputPdfStream);
    stamper = new PdfStamper(reader, outputPdfStream);
    // 保留该配置保证注释坐标可以直接匹配
    stamper.RotateContents = false;

    // 遍历页面查找便签
    for (int x = 1; x <= reader.NumberOfPages; x++)
    {
        PdfDictionary page = reader.GetPageN(x);
        pdfContentByte = stamper.GetOverContent(x);
        PdfArray annots = page.GetAsArray(PdfName.ANNOTS);
        // 新增：获取当前页面旋转角度和页面尺寸
        int pageRotation = reader.GetPageRotation(x);
        Rectangle pageSize = reader.GetPageSize(x);
        float pageWidth = pageSize.Width;
        float pageHeight = pageSize.Height;

        try
        {
            for (int i = 0; i < annots.Count(); i++)
            {
                PdfDictionary sticky = annots.GetAsDict(i);
                PdfArray stickyRect = sticky.GetAsArray(PdfName.RECT);
                // 获取便签坐标
                stickyRectangle = new PdfRectangle(
                    stickyRect.GetAsNumber(0).FloatValue, stickyRect.GetAsNumber(1).FloatValue,
                    stickyRect.GetAsNumber(2).FloatValue, stickyRect.GetAsNumber(3).FloatValue
                );
                
                string Content = "";
                try
                {
                    Content = sticky.GetAsString(PdfName.CONTENTS).ToString();
                }
                catch
                {
                    Content = "";
                }

                if (Content.ToString().Trim().ToLower() == "trinhky")
                {
                    // 传入新增的页面参数
                    GetHinhAnh(txtUserTrinhKy.Text, pageRotation, pageWidth, pageHeight);
                }
            }
        }
        catch { }
    }
    // 移除所有便签（需要时取消注释）
    // reader.RemoveAnnotations();
    // 释放资源
    stamper.Close();
    reader.Close();
    inputPdfStream.Close();
    outputPdfStream.Close();
}

修改GetHinhAnh方法 #

public void GetHinhAnh(string UserName, int pageRotation, float pageWidth, float pageHeight)
{
    try
    {
        // 获取签名图片
        System.Drawing.Image chuky = ((System.Drawing.Image)(Properties.Resources.ResourceManager.GetObject(UserName)));
        // 转换为iTextSharp支持的图片格式
        iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(chuky, iTextSharp.text.BaseColor.WHITE, false);

        float imgWidth = 100;
        float imgHeight = 80;
        image.ScaleAbsolute(imgWidth, imgHeight);

        float finalX = stickyRectangle.Left;
        float finalY = stickyRectangle.Bottom;

        // 根据页面旋转角度反向调整图片旋转和坐标，抵消页面旋转影响
        switch (pageRotation)
        {
            case 90:
                image.RotationDegrees = -90;
                finalX = pageWidth - stickyRectangle.Bottom - imgHeight;
                finalY = stickyRectangle.Left;
                break;
            case 180:
                image.RotationDegrees = -180;
                finalX = pageWidth - stickyRectangle.Left - imgWidth;
                finalY = pageHeight - stickyRectangle.Bottom - imgHeight;
                break;
            case 270:
                // 适配270度旋转的测试场景
                image.RotationDegrees = -270;
                finalX = stickyRectangle.Bottom;
                finalY = pageHeight - stickyRectangle.Left - imgWidth;
                break;
            default:
                // 无旋转页面无需调整
                break;
        }

        image.SetAbsolutePosition(finalX, finalY); 
        pdfContentByte.AddImage(image);
    }
    catch { }
}

内容的提问来源于stack exchange，提问作者Hoàng Nhân