Add Backgrounds in PDF ​

using ComPDFKit.PDFDocument;
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Runtime.InteropServices; 

namespace BackgroundTest
{
    internal class BackgroundTest
    {
        static private string outputPath = Path.GetDirectoryName(Path.GetDirectoryName(Path.GetDirectoryName(System.IO.Directory.GetCurrentDirectory()))) + "\\Output\\Background";
        static void Main(string[] args)
        {
            Console.WriteLine("Running Watermark test sample…\r\n");
            SDKLicenseHelper.LicenseVerify();
            CPDFDocument document = CPDFDocument.InitWithFilePath("CommonFivePage.pdf");
            if (!Directory.Exists(outputPath))
            {
                Directory.CreateDirectory(outputPath);
            }

            #region Sample 1: Add color background
            if (AddColorBackground(document))
            {
                Console.WriteLine("Add color background done.");
            }
            else
            {
                Console.WriteLine("Add color background  failed.");
            }
            document.Release();

            Console.WriteLine("--------------------");
            #endregion

            #region Sample 2: Add image background
            document = CPDFDocument.InitWithFilePath("CommonFivePage.pdf");
            if (AddImageBackground(document))
            {
                Console.WriteLine("Add image background done.");
            }
            else
            {
                Console.WriteLine("Add image background failed.");
            }
            document.Release();
            Console.WriteLine("--------------------");
            #endregion

            #region Remove background
            CPDFDocument colorBgDocument = CPDFDocument.InitWithFilePath("ColorBackground.pdf");
            CPDFDocument imageBgDocument = CPDFDocument.InitWithFilePath("ImageBackground.pdf");

            if (RemoveBackground(colorBgDocument, imageBgDocument))
            {
                Console.WriteLine("Remove background done.");
            }
            else
            {
                Console.WriteLine("Remove background failed.");
            }
            colorBgDocument.Release();
            imageBgDocument.Release();
            Console.WriteLine("--------------------");
            #endregion

            Console.WriteLine("Done!");
            Console.WriteLine("--------------------");
            Console.ReadLine();
        }

        /// <summary>
        /// Add color background                    
        /// </summary>
        /// <param name="document">Regular document</param> 
        static private bool AddColorBackground(CPDFDocument document)
        {
            CPDFBackground background = document.GetBackground();
            background.SetBackgroundType(C_Background_Type.BG_TYPE_COLOR);
            background.SetColor(new byte[] { 255, 0, 0 });
            background.SetOpacity(255);//0-255
            background.SetScale(1);//1 == 100%
            background.SetRotation(0);//Use radians
            background.SetHorizalign(C_Background_Horizalign.BG_HORIZALIGN_CENTER);
            background.SetVertalign(C_Background_Vertalign.BG_VERTALIGN_CENTER);
            background.SetXOffset(0);
            background.SetYOffset(0);
            background.SetPages("0-2");//Page numbering from 0
            background.Update();//Note: update after setup is complete
            string path = outputPath + "\\AddColorBackgroundTest.pdf";
            if (!document.WriteToFilePath(path))
            {
                return false;
            }
            Console.WriteLine("Browse the changed file in " + path);

            return true;
        }

        /// <summary>
        ///  Convert the bitmap to an array that can be set as an image watermark
        /// </summary>
        /// <param name="bitmap">Image source to be used as a image watermark.</param>
        /// <returns>An array for setting image</returns>
        public static byte[] BitmapToByteArray(Bitmap bitmap)
        {

            BitmapData bmpdata = null;

            try
            {
                bmpdata = bitmap.LockBits(new Rectangle(0, 0, bitmap.Width, bitmap.Height), ImageLockMode.ReadOnly, bitmap.PixelFormat);
                int numbytes = bmpdata.Stride * bitmap.Height;
                byte[] bytedata = new byte[numbytes];
                IntPtr ptr = bmpdata.Scan0;

                Marshal.Copy(ptr, bytedata, 0, numbytes);

                return bytedata;
            }
            finally
            {
                if (bmpdata != null)
                    bitmap.UnlockBits(bmpdata);
            }

        }

        /// <summary>
        /// Add image background.
        /// </summary>
        /// <param name="document">Regular document</param>
        static private bool AddImageBackground(CPDFDocument document)
        {
            CPDFBackground background = document.GetBackground();
            background.SetBackgroundType(C_Background_Type.BG_TYPE_IMAGE);
            Bitmap bitmap = new Bitmap("logo.png");
            background.SetImage(BitmapToByteArray(bitmap), bitmap.Width, bitmap.Height, ComPDFKit.Import.C_Scale_Type.fitCenter);
            background.SetOpacity(128);//0-255
            background.SetScale(1);//1 == 100%
            background.SetRotation(1f);//Use radians
            background.SetHorizalign(C_Background_Horizalign.BG_HORIZALIGN_CENTER);
            background.SetVertalign(C_Background_Vertalign.BG_VERTALIGN_CENTER);
            background.SetXOffset(0);
            background.SetYOffset(0);
            background.SetPages("0-2");//Page numbering from 0
            background.Update();//Note: update after setup is complete
            string path = outputPath + "\\AddImageBackgroundTest.pdf";
            if (!document.WriteToFilePath(path))
            {                                                
                return false;
            }
            Console.WriteLine("Browse the changed file in " + path);

            return true;
        }

        /// <summary>
        /// Check background type, and remove background. 
        /// </summary>
        /// <param name="colorBgDocument">Document with clolor background.78</param>
        /// <param name="imageBgDocument">Document with image background.</param>  
        /// <returns></returns>
        static private bool RemoveBackground(CPDFDocument colorBgDocument, CPDFDocument imageBgDocument)
        {
            CPDFBackground colorBackground = colorBgDocument.GetBackground();
            if(colorBackground.GetBackgroundType() != C_Background_Type.BG_TYPE_COLOR)
            {
                return false;
            } 

            colorBackground.Clear();
            string path1 = outputPath + "\\ClearColorBgTest.pdf";
            if (!colorBgDocument.WriteToFilePath(path1))
            {
                return false;
            }
            Console.WriteLine("Browse the changed file in " + path1);

            CPDFBackground imageBackground = imageBgDocument.GetBackground();
            if(imageBackground.GetBackgroundType()!= C_Background_Type.BG_TYPE_IMAGE)
            {
                return false;
            }

            imageBackground.Clear();
            string path2 = outputPath + "\\ClearImageBgTest.pdf";
            if (!imageBgDocument.WriteToFilePath(path2))
            {
                return false;
            }
            Console.WriteLine("Browse the changed file in " + path2);

            return true;
        }
    }
}