/// <summary>
/// 替换PDF中的图片
/// </summary>
/// <param name="src">pdf文件流</param>
/// <param name="distinguishMethod">识别需要被替换图片的方法</param>
/// <param name="replaceToImg">替换成这个图片</param>
/// <returns></returns>
private static MemoryStream ReplaceImage(Stream src, DistinguishImage distinguishMethod, Image replaceToImg)
{
PdfReader reader2 = new PdfReader(src);
PdfMemoryStream outMemoryStream = new PdfMemoryStream();
outMemoryStream.AllowClose = false;
using (PdfStamper stamper = new PdfStamper(reader2, outMemoryStream))
{
int pageCount2 = reader2.NumberOfPages;
for (int i = 1; i <= pageCount2; i++)
{
//Get the page
var page = reader2.GetPageN(i);
PdfObject obj = FindImageInPDFDictionary(page, distinguishMethod);
if (obj != null)
{
PdfReader.KillIndirect(obj);//移除老图片
//Image img = Image.GetInstance(replaceToImg, BaseColor.WHITE, true);
Image img = Image.GetInstance(replaceToImg);
Image maskImage = img.ImageMask;
if (maskImage != null)
{
stamper.Writer.AddDirectImageSimple(maskImage);
stamper.Writer.AddDirectImageSimple(img, (PRIndirectReference)obj);
}
}
}
}
outMemoryStream.Position = 0;
return(outMemoryStream);
}
//在pdf页面中 找到logo图片
private static PdfObject FindImageInPDFDictionary(PdfDictionary pg, DistinguishImage distinguishMethod)
{
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)
{
Console.WriteLine(name.ToString());
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))
{
if (distinguishMethod(tg) == true)
{
return(obj);
}
else
{
continue;//继续找
}
}// image inside a form
else if (PdfName.FORM.Equals(type))
{
return(FindImageInPDFDictionary(tg, distinguishMethod));
} //image inside a group
else if (PdfName.GROUP.Equals(type))
{
return(FindImageInPDFDictionary(tg, distinguishMethod));
}
}
}
}
return(null);
}