PdfDocument doc = new PdfDocument();
//Load file from disk.
doc.LoadFromFile(@"test.pdf");
//Get the first page.
PdfPageBase page = doc.Pages[0];
//Create PdfImageHelper object to get Image from page
PdfImageHelper helper = new PdfImageHelper();
Spire.Pdf.Utilities.PdfImageInfo[] images = helper.GetImagesInfo(page);
//Replace the first image on the page.
helper.ReplaceImage(images[0], PdfImage.FromFile(@"12.png"));
String result = "ReplaceImage_out2.pdf";
//Save the document
doc.SaveToFile(result);
PdfDocument doc = new PdfDocument();
doc.LoadFromFile(@"test2.pdf");
PdfPageBase page = doc.Pages[0];
PdfImageHelper helper = new PdfImageHelper();
Spire.Pdf.Utilities.PdfImageInfo[] images = helper.GetImagesInfo(page);
//删除原有图片
RectangleF rf= images[0].Bounds;
helper.DeleteImage(images[0]);
PdfImage image = PdfImage.FromFile(@"12.png");
//设置透明度绘制新图片
page.Canvas.SetTransparency(0.8f);
page.Canvas.DrawImage(image, rf);
String result = @"out.pdf";
doc.SaveToFile(result);
//加载原 PDF
PdfDocument doc = new PdfDocument();
doc.LoadFromFile(@"test2.pdf");
PdfPageBase page = doc.Pages[0];
//获取并删除原有图片
PdfImageHelper helper = new PdfImageHelper();
PdfImageInfo[] images = helper.GetImagesInfo(page);
RectangleF imageBounds = images[0].Bounds;
helper.DeleteImage(images[0]);
//创建新 PDF,添加与原页面相同大小的页面
PdfDocument newDoc = new PdfDocument();
PdfPageBase newPage = newDoc.Pages.Add(page.Size, new PdfMargins(0));
//在新页面的底层绘制新图片
PdfImage newImage = PdfImage.FromFile(@"IMG.png");
newPage.Canvas.DrawImage(newImage, imageBounds);
// 将原页面作为模板绘制到新页面的上层
PdfTemplate template = page.CreateTemplate();
newPage.Canvas.DrawTemplate(template, new PointF(0,0));
//保存并关闭文档
newDoc.SaveToFile(@"OUT.PDF");
newDoc.Close();
doc.Close();