How to: Custom Draw in the PDF Viewer

  • 3 minutes to read

The PDF Viewer can draw graphics in the PDF document in the Control.Paint event handler.

In this example, the filled rectangle is drawn at any document space when you hold down the left mouse button and move it.

The PDF Viewer gets the mouse position relative to the document by calling the PdfViewer.GetDocumentPosition method in the MouseDown (when the left mouse is pressed), and MouseMove event handlers (when the mouse is moving).

To draw a filled rectangle, the RectangleF.FromLTRB method is called in the Paint event handler. The start and end client points are obtained using the document position in the PdfViewer.GetClientPoint method.

This example also shows how to draw a rectangle using the Graphics.FillRectangle method.

using DevExpress.Pdf;
using System;
using System.Drawing;
using System.Windows.Forms;

namespace CustomDraw
{
    public partial class Form1 : Form
    {

        public Form1()
        {
            InitializeComponent();
            pdfViewer1.MouseDown += pdfViewer1_MouseDown;
            pdfViewer1.MouseMove += pdfViewer1_MouseMove;
            pdfViewer1.MouseUp += pdfViewer1_MouseUp;
            pdfViewer1.Paint += pdfViewer1_Paint;
        }

        bool mouseButtonPressed = false;
        PdfDocumentPosition startPosition;
        PdfDocumentPosition endPosition;

        void pdfViewer1_MouseDown(object sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                startPosition = pdfViewer1.GetDocumentPosition(e.Location);
                endPosition = null;
                mouseButtonPressed = true;
                pdfViewer1.Invalidate();
            }
        }

        void pdfViewer1_MouseMove(object sender, MouseEventArgs e)
        {
            if (mouseButtonPressed)
            {
                endPosition = pdfViewer1.GetDocumentPosition(e.Location);
                pdfViewer1.Invalidate();
            }
        }

        void pdfViewer1_MouseUp(object sender, MouseEventArgs e)
        {
            mouseButtonPressed = false;
        }

        void pdfViewer1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            g.DrawRectangle(Pens.Red, new Rectangle(150, 150, 800, 50));

            if (startPosition != null && endPosition != null)
            {
                PointF startPoint = pdfViewer1.GetClientPoint(startPosition);
                PointF endPoint = pdfViewer1.GetClientPoint(endPosition);

                g.FillRectangle(new SolidBrush(Color.FromArgb(128, Color.Aqua)),
                    RectangleF.FromLTRB(Math.Min(startPoint.X, endPoint.X), Math.Min(startPoint.Y, endPoint.Y),
                    Math.Max(startPoint.X, endPoint.X), Math.Max(startPoint.Y, endPoint.Y)));
            }
        }
    }
}