C# 通过iTextSharp实现关键字签字盖章(通过在内容中插入盖章图片的形式)

此功能通过 iTextSharp 读取PDF文档信息，并循环查找每一页PDF文件，在整个PDF中只要是符合条件的地方都会盖章，如只需要在最后一页盖章，请将方法中For循环去掉，并将

PdfContentByte contentByte = pdfStamper.GetUnderContent(i);
parser.ProcessContent<PdfLocation>(i, location);

改为

// 获得文档页数
int pdfPageSize = pdfReader.NumberOfPages;
//文档最后一页，如需要第一页则直接将pdfPageSize改为1
PdfContentByte contentByte = pdfStamper.GetUnderContent(pdfPageSize);
//读取文档最后一页内容
parser.ProcessContent<PdfLocation>(pdfPageSize, location);

这几句改掉之后即可精确到第几页盖章

以下为具体代码实现：

1、具体盖章实现，引用 iTextSharp.text.pdf

     /// 
/// pdf签字签章，以图片形式/// public class PDFSealHelper{/// 
/// 图片最大宽度/// private static float ReSizeMaxWidth = 50;/// 
/// 图片最大高度/// private static float ReSizeMaxHeight = 50;/// 
/// 签字盖章(文件流和Base64格式图片)/// /// 需要签字盖章byte数组的pdf文件/// 签字盖章后输出pdf路径/// Base64格式图片/// 关键字public static void SignBase64Img(byte[] bytePdf, string outPdfPath, string SignImgBase64, string SignKeyWord){System.IO.Stream outputPdfStream = new System.IO.FileStream(outPdfPath, System.IO.FileMode.Create, System.IO.FileAccess.Write, System.IO.FileShare.None);// 创建一个PdfReader对象PdfReader pdfReader = new PdfReader(bytePdf);PdfStamper pdfStamper = new PdfStamper(pdfReader, outputPdfStream);{// 获得文档页数int pdfPageSize = pdfReader.NumberOfPages;for (int i = 1; i <= pdfPageSize; i++){//获取当前页PdfContentByte contentByte = pdfStamper.GetUnderContent(i);PdfLocation location = new PdfLocation();iTextSharp.text.pdf.parser.PdfReaderContentParser parser = new iTextSharp.text.pdf.parser.PdfReaderContentParser(pdfReader);parser.ProcessContent<PdfLocation>(i, location);//查找当前页的关键字location.SearchKeywords(SignKeyWord);if (location.TextLocationInfo.Count > 0){//坐标是从左下角往上，左下角为(0,0)零点XTextInfo o = location.TextLocationInfo[0];//获取关键字左上角开始坐标var ltLocation = o.TopLeft.ToString().Split(',');//272.15,766.46,1var leftX = float.Parse(ltLocation[0]);var topY = float.Parse(ltLocation[1]);//获取关键字右下角结束坐标var rbLocation = o.BottomRight.ToString().Split(',');//305.15,755.46,1var rightX = float.Parse(rbLocation[0]);var bottomY = float.Parse(rbLocation[1]);//计算得到关键字的中心点float x = (rightX - leftX) / 2 + leftX;float y = (topY - bottomY) / 2 + bottomY;var imageByByte = ConvertBase64ToImage(SignImgBase64);//创建一个图片对象iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(imageByByte, System.Drawing.Imaging.ImageFormat.Jpeg);//设置图片的指定大小float expectWidth = image.Width;float expectHeight = image.Height;if (image.Width > image.Height && image.Width > ReSizeMaxWidth){expectWidth = ReSizeMaxWidth;expectHeight = expectWidth * image.Height / image.Width;}else if (image.Height > image.Width && image.Height > ReSizeMaxHeight){expectHeight = ReSizeMaxHeight;expectWidth = expectHeight * image.Width / image.Height;}//设置图片的指定大小image.ScalePercent(40);//image.ScaleToFit(expectWidth, expectHeight);//盖章位置于关键字右下方image.SetAbsolutePosition(x + (expectWidth / 2), y + (expectHeight / 2) - expectHeight);contentByte.AddImage(image);}}pdfStamper.Close();pdfReader.Close();System.Diagnostics.Process.Start(outPdfPath);}}/// 
/// 签字盖章(文件路径)/// /// 要签字盖章的pdf文件路径/// 签字盖章后输出pdf路径/// 签字的图片路径/// 关键字public static void SignFile(string pdfPath, string outPdfPath, string SignImgPath, string SignKeyWord){//创建盖章后生成pdfSystem.IO.Stream outputPdfStream = new System.IO.FileStream(outPdfPath, System.IO.FileMode.Create, System.IO.FileAccess.Write, System.IO.FileShare.None);// 创建一个PdfReader对象PdfReader pdfReader = new PdfReader(pdfPath);PdfStamper pdfStamper = new PdfStamper(pdfReader, outputPdfStream);// 获得文档页数int pdfPageSize = pdfReader.NumberOfPages;//循环每一页for (int i = 1; i <= pdfPageSize; i++){//获取当前页//GetUnderContent 加在内容下层//GetOverContent 加在内容上层PdfContentByte contentByte = pdfStamper.GetUnderContent(i);PdfLocation location = new PdfLocation();iTextSharp.text.pdf.parser.PdfReaderContentParser parser = new iTextSharp.text.pdf.parser.PdfReaderContentParser(pdfReader);parser.ProcessContent<PdfLocation>(i, location);//查找当前页的关键字及其坐标location.SearchKeywords(SignKeyWord);if (location.TextLocationInfo.Count > 0){XTextInfo o = location.TextLocationInfo[0];//获取关键字左上角开始坐标var ltLocation = o.TopLeft.ToString().Split(',');//272.15,766.46,1var leftX = float.Parse(ltLocation[0]);var topY = float.Parse(ltLocation[1]);//获取关键字右下角结束坐标var rbLocation = o.BottomRight.ToString().Split(',');//305.15,755.46,1var rightX = float.Parse(rbLocation[0]);var bottomY = float.Parse(rbLocation[1]);//计算得到关键字的中心点float x = (rightX - leftX) / 2 + leftX;float y = (topY - bottomY) / 2 + bottomY;//创建一个图片对象iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(SignImgPath);float expectWidth = image.Width;float expectHeight = image.Height;if (image.Width > image.Height && image.Width > ReSizeMaxWidth){expectWidth = ReSizeMaxWidth;expectHeight = expectWidth * image.Height / image.Width;}else if (image.Height > image.Width && image.Height > ReSizeMaxHeight){expectHeight = ReSizeMaxHeight;expectWidth = expectHeight * image.Width / image.Height;}//设置图片的指定大小image.ScalePercent(40);//image.ScaleToFit(expectWidth, expectHeight);//盖章位置于关键字右下方image.SetAbsolutePosition(x + (expectWidth / 2), y + (expectHeight / 2) - expectHeight);contentByte.AddImage(image);}}pdfStamper.Close();pdfReader.Close();System.Diagnostics.Process.Start(outPdfPath);}/// 
/// Base64转图片/// /// /// private static System.Drawing.Image ConvertBase64ToImage(string base64String){byte[] imageBytes = Convert.FromBase64String(base64String);System.Drawing.Bitmap bitmap = null;MemoryStream stream = null;stream = new MemoryStream(imageBytes);bitmap = new System.Drawing.Bitmap(stream);return bitmap;}}

2、查找pdf关键字坐标类，引用 iTextSharp.text.pdf.parser

    public class PdfLocation : LocationTextExtractionStrategy{/// 
/// 文档文本及坐标/// public List<XTextChunk> LocationResult = new List<XTextChunk>();/// 
/// 关键字及其坐标/// public List<XTextInfo> TextLocationInfo = new List<XTextInfo>();/// 
/// 重写读取文档文本方法,第一步就是执行此方法，不可删除，/// 删除后LocationResult数据为空，影响关键字坐标查找方法执行/// /// 文本渲染信息public override void RenderText(TextRenderInfo renderInfo){LineSegment segment = renderInfo.GetBaseline();XTextChunk location = new XTextChunk(renderInfo.GetText(), segment.GetStartPoint(), segment.GetEndPoint(), renderInfo.GetSingleSpaceWidth(), renderInfo.GetAscentLine(), renderInfo.GetDescentLine());LocationResult.Add(location);}/// 
/// 关键字坐标查找/// /// 关键字public void SearchKeywords(string sKeyword){var keyWordLen = sKeyword.Length;var keyWordList = sKeyword.ToList();LocationResult.Sort();TextLocationInfo.Clear();XTextInfo lastXTextInfo = new XTextInfo();if (LocationResult != null && LocationResult.Any()){for (int i = 0; i < LocationResult.Count; i++){//当关键字的第一个字匹配上后循环匹配后面的几个关键字if (LocationResult[i].Text == keyWordList[0].ToString()){if (keyWordLen > 1){for (int j = 0; j < keyWordList.Count; j++){//往后几个字符都符合关键字if (LocationResult[i + j].Text == keyWordList[j].ToString()){lastXTextInfo.appendText(LocationResult[i + j]);}}}else{lastXTextInfo.appendText(LocationResult[i]);}if (lastXTextInfo.Text.Contains(sKeyword)){TextLocationInfo.Add(lastXTextInfo);break;}}}}}}/// 
/// 文本块/// public class XTextChunk : IComparable, ICloneable{#region 字段/// 
/// 上升线段/// public LineSegment AscentLine { get; set; }/// 
/// 下降线段/// public LineSegment DecentLine { get; set; }/// 
/// 方向/// public Vector OrientationVector { get; set; }/// 
/// 文本/// public string Text { get; set; }/// 
/// 字符宽度/// public float CharSpaceWidth { get; set; }/// 
/// 平行距离开始/// public float DistParallelStart { get; set; }/// 
/// 平行距离结束/// public float DistParallelEnd { get; set; }/// 
/// 垂直距离/// public int DistPerpendicular { get; set; }/// 
/// 方向幅值(坐标角度)/// public int OrientationMagnitude { get; set; }/// 
/// 开始坐标/// public Vector StartLocation { get; set; }/// 
/// 结束坐标/// public Vector EndLocation { get; set; }#endregion/// 
/// 文本块、它的方向以及相对于方向向量的位置/// /// /// /// /// public XTextChunk(string txt, Vector startLoc, Vector endLoc, float charSpaceWidth, LineSegment ascentLine, LineSegment decentLine){Text = txt;StartLocation = startLoc;EndLocation = endLoc;CharSpaceWidth = charSpaceWidth;AscentLine = ascentLine;DecentLine = decentLine;OrientationVector = EndLocation.Subtract(StartLocation).Normalize();OrientationMagnitude = (int)(Math.Atan2(OrientationVector[Vector.I2], OrientationVector[Vector.I1]) * 1000);Vector origin = new Vector(0, 0, 1);DistPerpendicular = (int)(StartLocation.Subtract(origin)).Cross(OrientationVector)[Vector.I3];DistParallelStart = OrientationVector.Dot(StartLocation);DistParallelEnd = OrientationVector.Dot(EndLocation);}/// 
/// 创建作为当前实例副本的新对象。/// /// public object Clone(){XTextChunk copy = new XTextChunk(Text, StartLocation, EndLocation, CharSpaceWidth, AscentLine, DecentLine);return copy;}/// 
/// 根据方向、垂直距离和平行距离进行比较/// /// /// public int CompareTo(object obj){if (obj == null) {throw new Exception ("obj参数为空");}XTextChunk rhs = obj as XTextChunk;if (rhs != null){if (this == rhs) { return 0; }int rslt = OrientationMagnitude - rhs.OrientationMagnitude;if (rslt != 0) { return rslt; }rslt = DistPerpendicular - rhs.DistPerpendicular;if (rslt != 0) { return rslt; }//注意：检查浮点数是否相等是不安全的，如果两个块//真的在彼此之上，哪一个排在第一还是第二并不重要//所以我们任意选择了这种方式。rslt = DistParallelStart < rhs.DistParallelStart ? -1 : 1;return rslt;}else{throw new Exception ("XTextChunk为空");}}}/// 
/// 符合条件的文本信息/// public class XTextInfo{#region 字段/// 
/// 左上角开始坐标/// public Vector TopLeft { get; set; }/// 
/// 右下角结束坐标/// public Vector BottomRight { get; set; }/// 
/// 关键字/// public string Text { get; set; }#endregion#region 构造方法/// 
/// 构造方法/// /// public XTextInfo(XTextChunk initialXTextChunk){//上升线=AscentLineTopLeft = initialXTextChunk.AscentLine.GetStartPoint();BottomRight = initialXTextChunk.DecentLine.GetEndPoint();Text = initialXTextChunk.Text;}/// 
/// 构造方法/// public XTextInfo() { }#endregion/// 
/// 添加文本/// /// public void appendText(XTextChunk additionalXTextChunk){//DecentLine=下降线BottomRight = additionalXTextChunk.DecentLine.GetEndPoint();TopLeft = additionalXTextChunk.AscentLine.GetStartPoint();Text += additionalXTextChunk.Text;}}

仅个人记录，不喜勿喷，谢谢

参考文章：.net通过iTextSharp.pdf操作pdf文件实现查找关键字签字盖章

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