C# asp.net开源插件推荐：PdfiumViewer ( pdf 转成 图片png pdf convert to image )

// Define method to convert PDF to PNG
        public void ConvertPdfToPng(string pdfFilePath, string pngFileFolder, ImageFormat format)
        {
            // Set resolution (DPI)
            int dpi = 300;

            // Render PDF to image
            using (var document = PdfDocument.Load(pdfFilePath))
            {
                for (int i = 0; i < document.PageCount; i++)
                {
                    Thread.Sleep(100);
                    using (var image = document.Render(i, dpi, dpi, PdfRenderFlags.CorrectFromDpi))
                    {
                        var encoder = ImageCodecInfo.GetImageEncoders().First(c => c.FormatID == format.Guid);
                        var encParams = new EncoderParameters(1);
                        encParams.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 10L); //高质量
                        image.Save(pngFileFolder + i + ".png", encoder, encParams);

                    }
                }
            }
        }

 ConvertPdfToPng(inputPdfPath, outputImageFolder, ImageFormat.Png);