C#/VB.NET 实现彩色PDF转为灰度PDF

using Spire.Pdf.Conversion;

namespace ToGrayPDF
{
    class Program
    {
        static void Main(string[] args)
        {
            //创建一个PdfGrayConverter实例并加载文档
            PdfGrayConverter converter = new PdfGrayConverter("sample.pdf");

            //将彩色PDF转换为灰度
            converter.ToGrayPdf("Grayscale.pdf");
            converter.Dispose();
        }
    }
}

Imports Spire.Pdf.Conversion

Namespace ToGrayPDF
    Class Program
        Private Shared Sub Main(args As String())
            '创建一个PdfGrayConverter实例并加载文档
            Dim converter As New PdfGrayConverter("sample.pdf")

            '将彩色PDF转换为灰度
            converter.ToGrayPdf("Grayscale.pdf")
            converter.Dispose()
        End Sub
    End Class
End Namespace

public static Bitmap ChangeGray(Bitmap b) 
 { 
  BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, 
   PixelFORMat.Format24bppRgb); 
  int stride = bmData.Stride;   // 扫描的宽度 
   
   
  unsafe
  { 
   byte* p = (byte*)bmData.Scan0.ToPointer(); // 获取图像首地址 
   int nOffset = stride - b.Width * 3;  // 实际宽度与系统宽度的距离 
   byte red, green, blue; 
   for (int y = 0; y < b.Height; ++y) 
   { 
    for (int x = 0; x < b.Width; ++x) 
    { 
     blue = p[0]; 
     green = p[1]; 
     red = p[2]; 
   
     p[0] = p[1] = p[2] = (byte)(.299 * red + .587 * green + .114 * blue); // 转换公式 
     p += 3;  // 跳过3个字节处理下个像素点 
    } 
    p += nOffset; // 加上间隔 
   } 
  } 
  b.UnlockBits(bmData); // 解锁 
  return b; 
 }