使用iTextSharp提取图像
我一直使用这个代码，取得了很大的成功，拉出PDF的每个页面中find的第一个图像。 但是，由于一个不为人知的原因，现在不能使用一些新的PDF。 我已经使用其他工具（Datalogics等），这些新的PDF文件很好地提取图像。 但是，如果我可以使用iTextSharp，我不想购买Datalogics或任何工具。 有人可以告诉我为什么这个代码没有findPDF中的图像？
知道：我的PDF只有每页1个图像，没有别的。
using iTextSharp.text; using iTextSharp.text.pdf; ... public static void ExtractImagesFromPDF(string sourcePdf, string outputPath) { // NOTE: This will only get the first image it finds per page. PdfReader pdf = new PdfReader(sourcePdf); RandomAccessFileOrArray raf = new iTextSharp.text.pdf.RandomAccessFileOrArray(sourcePdf); try { for (int pageNumber = 1; pageNumber <= pdf.NumberOfPages; pageNumber++) { PdfDictionary pg = pdf.GetPageN(pageNumber); PdfDictionary res = (PdfDictionary)PdfReader.GetPdfObject(pg.Get(PdfName.RESOURCES)); PdfDictionary xobj = (PdfDictionary)PdfReader.GetPdfObject(res.Get(PdfName.XOBJECT)); if (xobj != null) { foreach (PdfName name in xobj.Keys) { PdfObject obj = xobj.Get(name); if (obj.IsIndirect()) { PdfDictionary tg = (PdfDictionary)PdfReader.GetPdfObject(obj); PdfName type = (PdfName)PdfReader.GetPdfObject(tg.Get(PdfName.SUBTYPE)); if (PdfName.IMAGE.Equals(type)) { int XrefIndex = Convert.ToInt32(((PRIndirectReference)obj).Number.ToString(System.Globalization.CultureInfo.InvariantCulture)); PdfObject pdfObj = pdf.GetPdfObject(XrefIndex); PdfStream pdfStrem = (PdfStream)pdfObj; byte[] bytes = PdfReader.GetStreamBytesRaw((PRStream)pdfStrem); if ((bytes != null)) { using (System.IO.MemoryStream memStream = new System.IO.MemoryStream(bytes)) { memStream.Position = 0; System.Drawing.Image img = System.Drawing.Image.FromStream(memStream); // must save the file while stream is open. if (!Directory.Exists(outputPath)) Directory.CreateDirectory(outputPath); string path = Path.Combine(outputPath, String.Format(@"{0}.jpg", pageNumber)); System.Drawing.Imaging.EncoderParameters parms = new System.Drawing.Imaging.EncoderParameters(1); parms.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Compression, 0); System.Drawing.Imaging.ImageCodecInfo jpegEncoder = Utilities.GetImageEncoder("JPEG"); img.Save(path, jpegEncoder, parms); break; } } } } } } } } catch { throw; } finally { pdf.Close(); raf.Close(); } } 我发现我的问题是我没有recursionsearch内部的forms和组图像。 基本上，原始代码只能findembedded在pdf文档根目录的图像。 这里是修改的方法加上一个新的方法（FindImageInPDFDictionary）recursionsearch页面中的图像。 注：仅支持JPEG和非压缩图像的缺陷仍然适用。 请参阅R Ubben的代码来解决这些缺陷。 HTH的人。
public static void ExtractImagesFromPDF(string sourcePdf, string outputPath) { // NOTE: This will only get the first image it finds per page. PdfReader pdf = new PdfReader(sourcePdf); RandomAccessFileOrArray raf = new iTextSharp.text.pdf.RandomAccessFileOrArray(sourcePdf); try { for (int pageNumber = 1; pageNumber <= pdf.NumberOfPages; pageNumber++) { PdfDictionary pg = pdf.GetPageN(pageNumber); // recursively search pages, forms and groups for images. PdfObject obj = FindImageInPDFDictionary(pg); if (obj != null) { int XrefIndex = Convert.ToInt32(((PRIndirectReference)obj).Number.ToString(System.Globalization.CultureInfo.InvariantCulture)); PdfObject pdfObj = pdf.GetPdfObject(XrefIndex); PdfStream pdfStrem = (PdfStream)pdfObj; byte[] bytes = PdfReader.GetStreamBytesRaw((PRStream)pdfStrem); if ((bytes != null)) { using (System.IO.MemoryStream memStream = new System.IO.MemoryStream(bytes)) { memStream.Position = 0; System.Drawing.Image img = System.Drawing.Image.FromStream(memStream); // must save the file while stream is open. if (!Directory.Exists(outputPath)) Directory.CreateDirectory(outputPath); string path = Path.Combine(outputPath, String.Format(@"{0}.jpg", pageNumber)); System.Drawing.Imaging.EncoderParameters parms = new System.Drawing.Imaging.EncoderParameters(1); parms.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Compression, 0); System.Drawing.Imaging.ImageCodecInfo jpegEncoder = Utilities.GetImageEncoder("JPEG"); img.Save(path, jpegEncoder, parms); } } } } } catch { throw; } finally { pdf.Close(); raf.Close(); } } private static PdfObject FindImageInPDFDictionary(PdfDictionary pg) { PdfDictionary res = (PdfDictionary)PdfReader.GetPdfObject(pg.Get(PdfName.RESOURCES)); PdfDictionary xobj = (PdfDictionary)PdfReader.GetPdfObject(res.Get(PdfName.XOBJECT)); if (xobj != null) { foreach (PdfName name in xobj.Keys) { PdfObject obj = xobj.Get(name); if (obj.IsIndirect()) { PdfDictionary tg = (PdfDictionary)PdfReader.GetPdfObject(obj); PdfName type = (PdfName)PdfReader.GetPdfObject(tg.Get(PdfName.SUBTYPE)); //image at the root of the pdf if (PdfName.IMAGE.Equals(type)) { return obj; }// image inside a form else if (PdfName.FORM.Equals(type)) { return FindImageInPDFDictionary(tg); } //image inside a group else if (PdfName.GROUP.Equals(type)) { return FindImageInPDFDictionary(tg); } } } } return null; }
这是一个更简单的解决scheme：
iTextSharp.text.pdf.parser.PdfImageObject pdfImage = new iTextSharp.text.pdf.parser.PdfImageObject(imgPRStream); System.Drawing.Image img = pdfImage.GetDrawingImage();
下面的代码结合了上面所有的Dave和R Ubben的想法，再加上它返回所有图像的完整列表，并且还处理多个位深度。 我不得不把它转换为VB的工作，虽然我很抱歉，…
Private Sub getAllImages(ByVal dict As pdf.PdfDictionary, ByVal images As List(Of Byte()), ByVal doc As pdf.PdfReader) Dim res As pdf.PdfDictionary = CType(pdf.PdfReader.GetPdfObject(dict.Get(pdf.PdfName.RESOURCES)), pdf.PdfDictionary) Dim xobj As pdf.PdfDictionary = CType(pdf.PdfReader.GetPdfObject(res.Get(pdf.PdfName.XOBJECT)), pdf.PdfDictionary) If xobj IsNot Nothing Then For Each name As pdf.PdfName In xobj.Keys Dim obj As pdf.PdfObject = xobj.Get(name) If (obj.IsIndirect) Then Dim tg As pdf.PdfDictionary = CType(pdf.PdfReader.GetPdfObject(obj), pdf.PdfDictionary) Dim subtype As pdf.PdfName = CType(pdf.PdfReader.GetPdfObject(tg.Get(pdf.PdfName.SUBTYPE)), pdf.PdfName) If pdf.PdfName.IMAGE.Equals(subtype) Then Dim xrefIdx As Integer = CType(obj, pdf.PRIndirectReference).Number Dim pdfObj As pdf.PdfObject = doc.GetPdfObject(xrefIdx) Dim str As pdf.PdfStream = CType(pdfObj, pdf.PdfStream) Dim bytes As Byte() = pdf.PdfReader.GetStreamBytesRaw(CType(str, pdf.PRStream)) Dim filter As String = tg.Get(pdf.PdfName.FILTER).ToString Dim width As String = tg.Get(pdf.PdfName.WIDTH).ToString Dim height As String = tg.Get(pdf.PdfName.HEIGHT).ToString Dim bpp As String = tg.Get(pdf.PdfName.BITSPERCOMPONENT).ToString If filter = "/FlateDecode" Then bytes = pdf.PdfReader.FlateDecode(bytes, True) Dim pixelFormat As System.Drawing.Imaging.PixelFormat Select Case Integer.Parse(bpp) Case 1 pixelFormat = Drawing.Imaging.PixelFormat.Format1bppIndexed Case 24 pixelFormat = Drawing.Imaging.PixelFormat.Format24bppRgb Case Else Throw New Exception("Unknown pixel format " + bpp) End Select Dim bmp As New System.Drawing.Bitmap(Int32.Parse(width), Int32.Parse(height), pixelFormat) Dim bmd As System.Drawing.Imaging.BitmapData = bmp.LockBits(New System.Drawing.Rectangle(0, 0, Int32.Parse(width), Int32.Parse(height)), System.Drawing.Imaging.ImageLockMode.WriteOnly, pixelFormat) Marshal.Copy(bytes, 0, bmd.Scan0, bytes.Length) bmp.UnlockBits(bmd) Using ms As New MemoryStream bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png) bytes = ms.GetBuffer End Using End If images.Add(bytes) ElseIf pdf.PdfName.FORM.Equals(subtype) Or pdf.PdfName.GROUP.Equals(subtype) Then getAllImages(tg, images, doc) End If End If Next End If End Sub
De c＃版本：
private IList<System.Drawing.Image> GetImagesFromPdfDict(PdfDictionary dict, PdfReader doc){ List<System.Drawing.Image> images = new List<System.Drawing.Image>(); PdfDictionary res = (PdfDictionary)(PdfReader.GetPdfObject(dict.Get(PdfName.RESOURCES))); PdfDictionary xobj = (PdfDictionary)(PdfReader.GetPdfObject(res.Get(PdfName.XOBJECT))); if (xobj != null) { foreach (PdfName name in xobj.Keys) { PdfObject obj = xobj.Get(name); if (obj.IsIndirect()) { PdfDictionary tg = (PdfDictionary)(PdfReader.GetPdfObject(obj)); pdf.PdfName subtype = (pdf.PdfName)(pdf.PdfReader.GetPdfObject(tg.Get(pdf.PdfName.SUBTYPE))); if (pdf.PdfName.IMAGE.Equals(subtype)) { int xrefIdx = ((pdf.PRIndirectReference)obj).Number; pdf.PdfObject pdfObj = doc.GetPdfObject(xrefIdx); pdf.PdfStream str = (pdf.PdfStream)(pdfObj); byte[] bytes = pdf.PdfReader.GetStreamBytesRaw((pdf.PRStream)str); string filter = tg.Get(pdf.PdfName.FILTER).ToString(); string width = tg.Get(pdf.PdfName.WIDTH).ToString(); string height = tg.Get(pdf.PdfName.HEIGHT).ToString(); string bpp = tg.Get(pdf.PdfName.BITSPERCOMPONENT).ToString(); if (filter == "/FlateDecode") { bytes = pdf.PdfReader.FlateDecode(bytes, true); System.Drawing.Imaging.PixelFormat pixelFormat; switch (int.Parse(bpp)) { case 1: pixelFormat = System.Drawing.Imaging.PixelFormat.Format1bppIndexed; break; case 24: pixelFormat = System.Drawing.Imaging.PixelFormat.Format24bppRgb; break; default: throw new Exception("Unknown pixel format " + bpp); } var bmp = new System.Drawing.Bitmap(Int32.Parse(width), Int32.Parse(height), pixelFormat); System.Drawing.Imaging.BitmapData bmd = bmp.LockBits(new System.Drawing.Rectangle(0, 0, Int32.Parse(width), Int32.Parse(height)), System.Drawing.Imaging.ImageLockMode.WriteOnly, pixelFormat); Marshal.Copy(bytes, 0, bmd.Scan0, bytes.Length); bmp.UnlockBits(bmd); using (var ms = new MemoryStream()) { bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Png); bytes = ms.GetBuffer(); } } images.Add(System.Drawing.Image.FromStream(new MemoryStream(bytes))); } else if (pdf.PdfName.FORM.Equals(subtype) || pdf.PdfName.GROUP.Equals(subtype)) { images.AddRange(GetImagesFromPdfDict(tg, doc)); } } } } return images; }
以上只能使用JPEG。 不包括embedded式图像和embedded式文件，您需要浏览IMAGE子types的对象，然后查看filter并采取适当的操作。 这是一个例子，假设我们有一个IMAGE子types的PdfObject：
PdfReader pdf = new PdfReader("c:\\temp\\exp0.pdf"); int xo=pdf.XrefSize; for (int i=0;i<xo;i++) { PdfObject obj=pdf.GetPdfObject(i); if (obj!=null && obj.IsStream()) { PdfDictionary pd=(PdfDictionary)obj; if (pd.Contains(PdfName.SUBTYPE) && pd.Get(PdfName.SUBTYPE).ToString()=="/Image") { string filter=pd.Get(PdfName.FILTER).ToString(); string width=pd.Get(PdfName.WIDTH).ToString(); string height=pd.Get(PdfName.HEIGHT).ToString(); string bpp=pd.Get(PdfName.BITSPERCOMPONENT).ToString(); string extent="."; byte [] img=null; switch (filter) { case "/FlateDecode": byte[] arr=PdfReader.FlateDecode(PdfReader.GetStreamBytesRaw((PRStream)obj),true); Bitmap bmp=new Bitmap(Int32.Parse(width),Int32.Parse(height),PixelFormat.Format24bppRgb); BitmapData bmd=bmp.LockBits(new Rectangle(0,0,Int32.Parse(width),Int32.Parse(height)),ImageLockMode.WriteOnly, PixelFormat.Format24bppRgb); Marshal.Copy(arr,0,bmd.Scan0,arr.Length); bmp.UnlockBits(bmd); bmp.Save("c:\\temp\\bmp1.png",ImageFormat.Png); break; default: break; } } } }
当然，由于Microsoft BGR，这会弄脏颜色，但我想保持简短。 为“/ CCITTFaxDecode”做类似的事情
这只是别人想法的另一种回应，而是为我工作的那个。 在这里，我用@马尔科的图像抓取片段与R Ubben的循环：
private IList<System.Drawing.Image> GetImagesFromPdfDict(PdfDictionary dict, PdfReader doc) { List<System.Drawing.Image> images = new List<System.Drawing.Image>(); PdfDictionary res = (PdfDictionary)(PdfReader.GetPdfObject(dict.Get(PdfName.RESOURCES))); PdfDictionary xobj = (PdfDictionary)(PdfReader.GetPdfObject(res.Get(PdfName.XOBJECT))); if (xobj != null) { foreach (PdfName name in xobj.Keys) { PdfObject obj = xobj.Get(name); if (obj.IsIndirect()) { PdfDictionary tg = (PdfDictionary)(PdfReader.GetPdfObject(obj)); PdfName subtype = (PdfName)(PdfReader.GetPdfObject(tg.Get(PdfName.SUBTYPE))); if (PdfName.IMAGE.Equals(subtype)) { int xrefIdx = ((PRIndirectReference)obj).Number; PdfObject pdfObj = doc.GetPdfObject(xrefIdx); PdfStream str = (PdfStream)(pdfObj); iTextSharp.text.pdf.parser.PdfImageObject pdfImage = new iTextSharp.text.pdf.parser.PdfImageObject((PRStream)str); System.Drawing.Image img = pdfImage.GetDrawingImage(); images.Add(img); } else if (PdfName.FORM.Equals(subtype) || PdfName.GROUP.Equals(subtype)) { images.AddRange(GetImagesFromPdfDict(tg, doc)); } } } } return images; }
