Spire.Pdf Prints PDF Files as Image PDF Files

The source file is a PDF composed of various points, lines, text, and tables, and all content needs to be converted into image format and stored in a PDF.

Introduction:

  <ItemGroup>
    <PackageReference Include="FreeSpire.PDF" Version="8.6.0" />
    <PackageReference Include="Microsoft.IO.RecyclableMemoryStream" Version="2.3.2" />
  </ItemGroup>

	internal class Program
	{
		private static readonly RecyclableMemoryStreamManager StreamManager = new();

		[SupportedOSPlatform("windows")]
		static async Task Main()
		{
			using PdfDocument oldPdf = new PdfDocument();
			using PdfDocument newPdf = new PdfDocument();

			oldPdf.LoadFromFile("old.pdf");
			for (int i = 0; i < oldPdf.Pages.Count; i++)
			{
				PdfPageBase oldPage = oldPdf.Pages[i];
				var newPage = newPdf.AppendPage();
				
				// Convert the page to an image
				Image image = oldPdf.SaveAsImage(i, PdfImageType.Bitmap);
				using var stream = StreamManager.GetStream();
				image.Save(stream, ImageFormat.Png);
				
				// Insert the image into the new PDF page
				var pdfImage = PdfImage.FromStream(stream);
				var size = GetSize(newPage, image);
				// Draw image and set coordinates
				newPage.Canvas.DrawImage(pdfImage, new PointF(0, 0), size);
			}
			newPdf.SaveToFile("new.pdf");
		}

		/// <summary>
		/// Resize image<br />
		/// If the image is too long or large, it will be automatically reduced.<br />
		/// If the image is small, it will be centered horizontally.
		/// </summary>
		/// <param name="page"></param>
		/// <param name="image"></param>
		/// <returns></returns>
		[SupportedOSPlatform("windows")]
		static SizeF GetSize(PdfPageBase page, Image image)
		{
			float x = 0;  // X coordinate of the image on the page
			// float y = 0;  // Y coordinate of the image on the page

			float imageWidth = image.Width;
			float imageHeight = image.Height;

			// ClientSize gives the actual displayable area after removing borders; Size is the full paper area
			var clientSize = page.GetClientSize();
			float pageWidth = clientSize.Width;
			float pageHeight = clientSize.Height;

			// Final calculated results
			float width = image.Width;
			float height = image.Height;

			// If the image is too long
			if (imageWidth >= pageWidth)
			{
				float ratio = imageWidth / pageWidth;
				width = pageWidth;
				height = imageHeight / ratio;
			}
			// Center the image if it is smaller than the page
			else if (imageHeight < pageWidth)
			{
				x = (pageWidth - imageWidth) / 2;
			}
			return new SizeF(width: width, height: height);
		}
	}