怎样去除PDF中的空白页 - GdPicture.NET使用教程

在PDF文件进行扫描的时候，有时PDF中会有一些空白页存在，扫描出来也是空白的，所以在扫描前往往需要加载GdPicture.NET，先一页一页的进行检查，这样往往会很麻烦，实际上在使用GdPicture.NET的时候，只需要几段简单的代码，就可以除去PDF中的空白页，这里提供一段示例代码，适用于GdPicture.NET 8.5.3或者更高的版本。

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示例代码如下：

const int RASTER_DPI = 200;            GdPictureImaging oGdPictureImaging = new GdPictureImaging();            GdPicturePDF oGdPicturePDF = new GdPicturePDF();            oGdPicturePDF.LoadFromFile(@"c:\input.pdf", false);            oGdPicturePDF.SetMeasurementUnit(PdfMeasurementUnit.PdfMeasurementUnitPoint);            oGdPicturePDF.EnableCompression(true);            for (int i = 1; i <= oGdPicturePDF.GetPageCount(); i++)            {                oGdPicturePDF.SelectPage(i);                int rasterImageID = oGdPicturePDF.RenderPageToGdPictureImageEx(RASTER_DPI, false);                int bitDepth = oGdPictureImaging.GetBitDepth(rasterImageID);                if (oGdPictureImaging.IsBlank(rasterImageID))                {                    //page is blank, we remove it                    oGdPicturePDF.DeletePage(i--);                }                else                {                    //if the page is based on a single color image, we convert it to 1bpp. Warning: not 100% safe                    if (bitDepth > 8 && !oGdPicturePDF.PageHasText() && !oGdPicturePDF.PageHasShape() && oGdPicturePDF.GetPageImageCount() == 1)                    {                        if (oGdPictureImaging.ConvertTo1BppAT(rasterImageID) == GdPictureStatus.OK)                        {                            //we remove the page then create a new one to remove unused resources on pack                            float pageWidth = oGdPicturePDF.GetPageWidth();                            float pageHeight = oGdPicturePDF.GetPageHeight();                            oGdPicturePDF.DeletePage(i);                            oGdPicturePDF.InsertPage(pageWidth, pageHeight, i);                            string pdfImageResName = oGdPicturePDF.AddImageFromGdPictureImage(rasterImageID, false, false);                            if (pdfImageResName != "")                            {                                oGdPicturePDF.DrawImage(pdfImageResName, 0, 0, pageWidth, pageHeight);                            }                            else                            {                                throw new Exception("Error embedding bitmap in PDF");                            }                        }                        else                        {                            throw new Exception("Error during bitmap thresholding");                        }                    }                }                oGdPictureImaging.ReleaseGdPictureImage(rasterImageID);            }            oGdPicturePDF.SaveToFile(@"c:\newpdf.pdf", true); //we have to pack the doc to remove unused enbedded bitmaps            oGdPicturePDF.CloseDocument();