Programming

At present, more and more e-books and e-magazines are created with PDF because people can insert beautiful images, flash or some other attractive elements in PDF, which make the e-books or e-magazines be more appealed for readers.

Besides inserting images or flash, sometimes, people may draw shapes or tables in PDF document according to the document contents. For example, if one paragraph has shown much data information, the author may create a data table to make reader learn clearly about the data.

But, there is a question. How to draw in PDF? And now, I want to talk something about how to draw shape in PDF.

Generally speaking, if we want to edit one PDF document, we need to use some professional tools. The most frequently used tool is Adobe Acrobat. People can follow the guide about how to use these tools to meet their requirements.

The method I introduce is how to draw shape by using C#. This method is useful for developers who want to create PDF drawing tools. And I use one component, Spire.PDF in this method.

The shapes I draw include star and circle.

using System;

using System.Drawing;

using Spire.Pdf;

using Spire.Pdf.Graphics;

namespace DrawShape

{

    class Program

    {

        static void Main(string[] args)

        {

            //Create a pdf document.

            PdfDocument doc = new PdfDocument();

            // Create one page

            PdfPageBase page = doc.Pages.Add();

            DrawSpiro(page);

            DrawPath(page);

            //Save pdf file.

            doc.SaveToFile("DrawShape.pdf");

            doc.Close();

            //Launching the Pdf file.

            System.Diagnostics.Process.Start("DrawShape.pdf");

        }

        private static void DrawPath(PdfPageBase page)

        {

            PointF[] points = new PointF[5];

            for (int i = 0; i < points.Length; i++)

            {

                float x = (float)Math.Cos(i * 2 * Math.PI / 5);

                float y = (float)Math.Sin(i * 2 * Math.PI / 5);

                points[i] = new PointF(x, y);

            }

            PdfPath path = new PdfPath();

            path.AddLine(points[2], points[0]);

            path.AddLine(points[0], points[3]);

            path.AddLine(points[3], points[1]);

            path.AddLine(points[1], points[4]);

            path.AddLine(points[4], points[2]);

            //save graphics state

            PdfGraphicsState state = page.Canvas.Save();

            PdfPen pen = new PdfPen(Color.DeepSkyBlue, 0.02f);

            PdfBrush brush1 = new PdfSolidBrush(Color.CadetBlue);

            page.Canvas.ScaleTransform(50f, 50f);

            page.Canvas.TranslateTransform(5f, 1.2f);

            page.Canvas.DrawPath(pen, path);

            page.Canvas.TranslateTransform(2f, 0f);

            path.FillMode = PdfFillMode.Alternate;

            page.Canvas.DrawPath(pen, brush1, path);

            page.Canvas.TranslateTransform(2f, 0f);

            path.FillMode = PdfFillMode.Winding;

            page.Canvas.DrawPath(pen, brush1, path);

            PdfLinearGradientBrush brush2

                = new PdfLinearGradientBrush(new PointF(-2, 0), new PointF(2, 0), Color.Red, Color.Blue);

            page.Canvas.TranslateTransform(-4f, 2f);

            path.FillMode = PdfFillMode.Alternate;

            page.Canvas.DrawPath(pen, brush2, path);

            PdfRadialGradientBrush brush3

                = new PdfRadialGradientBrush(new PointF(0f, 0f), 0f, new PointF(0f, 0f), 1f, Color.Red, Color.Blue);

            page.Canvas.TranslateTransform(2f, 0f);

            path.FillMode = PdfFillMode.Winding;

            page.Canvas.DrawPath(pen, brush3, path);

            PdfTilingBrush brush4 = new PdfTilingBrush(new RectangleF(0, 0, 4f, 4f));

            brush4.Graphics.DrawRectangle(brush2, 0, 0, 4f, 4f);

            page.Canvas.TranslateTransform(2f, 0f);

            path.FillMode = PdfFillMode.Winding;

            page.Canvas.DrawPath(pen, brush4, path);

            //restor graphics

            page.Canvas.Restore(state);

        }

        private static void DrawSpiro(PdfPageBase page)

        {

            //save graphics state

            PdfGraphicsState state = page.Canvas.Save();

            //Draw shap - spiro

            PdfPen pen = PdfPens.DeepSkyBlue;

            int nPoints = 1000;

            double r1 = 30;

            double r2 = 25;

            double p = 35;

            double x1 = r1 + r2 - p;

            double y1 = 0;

            double x2 = 0;

            double y2 = 0;

            page.Canvas.TranslateTransform(100, 100);

            for (int i = 0; i < nPoints; i++)

            {

                double t = i * Math.PI / 90;

                x2 = (r1 + r2) * Math.Cos(t) - p * Math.Cos((r1 + r2) * t / r2);

                y2 = (r1 + r2) * Math.Sin(t) - p * Math.Sin((r1 + r2) * t / r2);

                page.Canvas.DrawLine(pen, (float)x1, (float)y1, (float)x2, (float)y2);

                x1 = x2;

                y1 = y2;

            }

            //restor graphics

            page.Canvas.Restore(state);

        }

    }

}