PDF patterns and shadings in C#

//
// Copyright (c) 2001-2021 by PDFTron Systems Inc. All Rights Reserved.
//

using System;
using pdftron;
using pdftron.Common;
using pdftron.Filters;
using pdftron.SDF;
using pdftron.PDF;

using NUnit.Framework;

namespace MiscellaneousSamples
{
	/// <summary>
	/// This example illustrates how to create PDF patterns and shadings.
	/// </summary>
	class PatternTest
	{
		static PatternTest() {}
		
		// Relative path to the folder containing test files.
		const string input_path =  "TestFiles/";

		[Test]
		public static void Sample()
		{
			try	
			{
				using (PDFDoc doc = new PDFDoc())
				using (ElementWriter writer = new ElementWriter())
				using (ElementBuilder eb = new ElementBuilder())
				{
					// The following sample illustrates how to create and use tiling patterns
					Page page = doc.PageCreate();
					writer.Begin(page);

					Element element = eb.CreateTextBegin(Font.Create(doc, Font.StandardType1Font.e_times_bold), 1);
					writer.WriteElement(element);  // Begin the text block

					element = eb.CreateTextRun("G");
					element.SetTextMatrix(720, 0, 0, 720, 20, 240);
					GState gs = element.GetGState();
					gs.SetTextRenderMode(GState.TextRenderingMode.e_fill_stroke_text);
					gs.SetLineWidth(4);

					// Set the fill color space to the Pattern color space. 
					gs.SetFillColorSpace(ColorSpace.CreatePattern());
					gs.SetFillColor(CreateTilingPattern(doc));

					writer.WriteElement(element);
					writer.WriteElement(eb.CreateTextEnd()); // Finish the text block

					writer.End();	// Save the page
					doc.PagePushBack(page);
					//-----------------------------------------------

					/// The following sample illustrates how to create and use image tiling pattern
					page = doc.PageCreate();
					writer.Begin(page);
			
					eb.Reset();
					element = eb.CreateRect(0, 0, 612, 794);

					// Set the fill color space to the Pattern color space. 
					gs = element.GetGState();
					gs.SetFillColorSpace(ColorSpace.CreatePattern());
					gs.SetFillColor(CreateImageTilingPattern(doc));
					element.SetPathFill(true);		

					writer.WriteElement(element);

					writer.End();	// Save the page
					doc.PagePushBack(page);
					//-----------------------------------------------

					/// The following sample illustrates how to create and use PDF shadings
					page = doc.PageCreate();
					writer.Begin(page);

					eb.Reset();
					element = eb.CreateRect(0, 0, 612, 794);

					// Set the fill color space to the Pattern color space. 
					gs = element.GetGState();
					gs.SetFillColorSpace(ColorSpace.CreatePattern());
					gs.SetFillColor(CreateAxialShading(doc));
					element.SetPathFill(true);		

					writer.WriteElement(element);

					writer.End();	// save the page
					doc.PagePushBack(page);
					//-----------------------------------------------

					doc.Save(Utils.CreateExternalFile("patterns.pdf"), SDFDoc.SaveOptions.e_remove_unused);
					Console.WriteLine("Done. Result saved in patterns.pdf...");
				}
			}
			catch (PDFNetException e)
			{
				Console.WriteLine(e.Message);
				Assert.True(false);
			}
		}

		static PatternColor CreateTilingPattern(PDFDoc doc) 
		{
			using (ElementWriter writer = new ElementWriter())
			using (ElementBuilder eb = new ElementBuilder())
			{
				// Create a new pattern content stream - a heart. ------------
				writer.Begin(doc);
				eb.PathBegin();
				eb.MoveTo(0, 0);
				eb.CurveTo(500, 500, 125, 625, 0, 500);
				eb.CurveTo(-125, 625, -500, 500, 0, 0);
				Element heart = eb.PathEnd();
				heart.SetPathFill(true); 
	
				// Set heart color to red.
				heart.GetGState().SetFillColorSpace(ColorSpace.CreateDeviceRGB()); 
				heart.GetGState().SetFillColor(new ColorPt(1, 0, 0)); 
				writer.WriteElement(heart);

				Obj pattern_dict = writer.End();

				// Initialize pattern dictionary. For details on what each parameter represents please 
				// refer to Table 4.22 (Section '4.6.2 Tiling Patterns') in PDF Reference Manual.
				pattern_dict.PutName("Type", "Pattern");
				pattern_dict.PutNumber("PatternType", 1);

				// TilingType - Constant spacing.
				pattern_dict.PutNumber("TilingType", 1); 

				// This is a Type1 pattern - A colored tiling pattern.
				pattern_dict.PutNumber("PaintType", 1);

				// Set bounding box
				pattern_dict.PutRect("BBox", -253, 0, 253, 545);

				// Set the pattern matrix
				pattern_dict.PutMatrix("Matrix", new Matrix2D(0.04, 0, 0, 0.04, 0, 0));

				// Set the desired horizontal and vertical spacing between pattern cells, 
				// measured in the pattern coordinate system.
				pattern_dict.PutNumber("XStep", 1000);
				pattern_dict.PutNumber("YStep", 1000);
	
				return new PatternColor(pattern_dict); // finished creating the Pattern resource
			}
		}

		static PatternColor CreateImageTilingPattern(PDFDoc doc) 
		{
			using (ElementWriter writer = new ElementWriter())
			using (ElementBuilder eb = new ElementBuilder())
			{

				// Create a new pattern content stream - a single bitmap object ----------
				writer.Begin(doc);
				Image  img = Image.Create(doc, Utils.GetAssetTempFile(input_path + "butterfly.png"));
				Element img_element = eb.CreateImage(img, 0, 0, img.GetImageWidth(), img.GetImageHeight());
				writer.WritePlacedElement(img_element);
				Obj pattern_dict = writer.End();

				// Initialize pattern dictionary. For details on what each parameter represents please 
				// refer to Table 4.22 (Section '4.6.2 Tiling Patterns') in PDF Reference Manual.
				pattern_dict.PutName("Type", "Pattern");
				pattern_dict.PutNumber("PatternType", 1);

				// TilingType - Constant spacing.
				pattern_dict.PutNumber("TilingType", 1); 

				// This is a Type1 pattern - A colored tiling pattern.
				pattern_dict.PutNumber("PaintType", 1);

				// Set bounding box
				pattern_dict.PutRect("BBox", -253, 0, 253, 545);

				// Set the pattern matrix
				pattern_dict.PutMatrix("Matrix", new Matrix2D(0.3, 0, 0, 0.3, 0, 0));

				// Set the desired horizontal and vertical spacing between pattern cells, 
				// measured in the pattern coordinate system.
				pattern_dict.PutNumber("XStep", 300);
				pattern_dict.PutNumber("YStep", 300);
			
				return new PatternColor(pattern_dict); // finished creating the Pattern resource
			}
		}

		static PatternColor CreateAxialShading(PDFDoc doc) 
		{
			// Create a new Shading object ------------
			Obj pattern_dict = doc.CreateIndirectDict();

			// Initialize pattern dictionary. For details on what each parameter represents 
			// please refer to Tables 4.30 and 4.26 in PDF Reference Manual
			pattern_dict.PutName("Type", "Pattern");
			pattern_dict.PutNumber("PatternType", 2); // 2 stands for shading
					
			Obj shadingDict = pattern_dict.PutDict("Shading");
			shadingDict.PutNumber("ShadingType", 2);
			shadingDict.PutName("ColorSpace", "DeviceCMYK");
					
			// Set the coordinates of the axial shading to the output
			shadingDict.PutRect("Coords", 0, 0, 612, 794);

			// Set the Functions for the axial shading
			Obj funct = shadingDict.PutDict("Function");
			Obj C0 = funct.PutArray("C0");
			C0.PushBackNumber(1);
			C0.PushBackNumber(0);
			C0.PushBackNumber(0);
			C0.PushBackNumber(0);

			Obj C1 = funct.PutArray("C1");
			C1.PushBackNumber(0);
			C1.PushBackNumber(1);
			C1.PushBackNumber(0);
			C1.PushBackNumber(0);
					
			Obj domain = funct.PutArray("Domain");
			domain.PushBackNumber(0);
			domain.PushBackNumber(1);
			
			funct.PutNumber("FunctionType", 2);
			funct.PutNumber("N", 1);

			return new PatternColor(pattern_dict);
		}
	}
}