PdfGraphics.AddToPageBackground(PdfPage, Single, Single) Method

Adds graphics to a PDF page background with the specified horizontal and vertical resolutions.

Namespace: DevExpress.Pdf

Assembly: DevExpress.Pdf.v23.2.Drawing.dll

NuGet Package: DevExpress.Pdf.Drawing

Declaration

C#

public void AddToPageBackground(
    PdfPage page,
    float dpiX,
    float dpiY
)

VB.NET

Public Sub AddToPageBackground(
    page As PdfPage,
    dpiX As Single,
    dpiY As Single
)

Parameters

Name	Type	Description
page	PdfPage	A PdfPage object that is the page where graphics are drawn (measured in points - 1/72 of an inch).
dpiX	Single	A Single object that represents the value, in dots per inch, for the horizontal resolution.
dpiY	Single	A Single object that represents the value, in dots per inch, for the vertical resolution.

Remarks

Call the AddToPageBackground method to draw graphics as the background of the page. To draw graphics as the foreground of the page content, call the PdfGraphics.AddToPageForeground method.

The overloaded AddToPageBackground method automatically converts world coordinates to page coordinates. See Coordinate Systems to learn more.

The world coordinates (units) are converted to page coordinates (points) using the following formula:

x = (unitX / dpiX) * 72;

y = cropBoxHeight - (unitY / dpiY) * 72.

To render graphics on a PDF document page, pass 72 as a DPI value to this method. The DPI value you pass into this method does not affect graphics quality and used for coordinates transformation only (world coordinates to page coordinates). For example, the 72 DPI value allows you to transform coordinates without any scaling.

Example

View Example

Program.cs

using System.Drawing;
using System.Collections.Generic;
using DevExpress.Pdf;

const float DrawingDpi = 72f;

static void Main(string[] args)
{
    using (PdfDocumentProcessor processor = new PdfDocumentProcessor())
    {
        processor.LoadDocument("..\\..\\RotatedDocument.pdf");
        using (SolidBrush textBrush = new SolidBrush(Color.FromArgb(100, Color.Blue)))
            AddGraphics(processor, "text", textBrush);
        processor.SaveDocument("..\\..\\RotatedDocumentWithGraphics.pdf");
    }
}

static void AddGraphics(PdfDocumentProcessor processor, string text, SolidBrush textBrush)
{
    IList<PdfPage> pages = processor.Document.Pages;
    for (int i = 0; i < pages.Count; i++) {
        PdfPage page = pages[i];
        using (PdfGraphics graphics = processor.CreateGraphics())
        {
            SizeF actualPageSize = PrepareGraphics(page, graphics, DrawingDpi, DrawingDpi);
            using (Font font = new Font("Segoe UI", 20, FontStyle.Regular))
            {
                SizeF textSize =
                    graphics.MeasureString(text, font, PdfStringFormat.GenericDefault);
                PointF topLeft = new PointF(0, 0);
                PointF bottomRight =
                    new PointF(actualPageSize.Width - textSize.Width, actualPageSize.Height - textSize.Height);
                graphics.DrawString(text, font, textBrush, topLeft);
                graphics.DrawString(text, font, textBrush, bottomRight);
                graphics.AddToPageForeground(page, DrawingDpi, DrawingDpi);
            }
        }
    }
}

static SizeF PrepareGraphics(PdfPage page, PdfGraphics graphics, float dpiX, float dpiY) {
    PdfRectangle cropBox = page.CropBox;
    float cropBoxWidth = ConvertFromPdfUnits((float)cropBox.Width, dpiX);
    float cropBoxHeight = ConvertFromPdfUnits((float)cropBox.Height, dpiY);
    switch(page.Rotate) {
        case 90:
            graphics.RotateTransform(-90);
            graphics.TranslateTransform(-cropBoxHeight, 0);
            return new SizeF(cropBoxHeight, cropBoxWidth);
        case 180:
            graphics.RotateTransform(-180);
            graphics.TranslateTransform(-cropBoxWidth, -cropBoxHeight);
            return new SizeF(cropBoxWidth, cropBoxHeight);
        case 270:
            graphics.RotateTransform(-270);
            graphics.TranslateTransform(0, -cropBoxWidth);
            return new SizeF(cropBoxHeight, cropBoxWidth);
    }
    return new SizeF(cropBoxWidth, cropBoxHeight);
}

static float ConvertFromPdfUnits(float pdfValue, float targetDpi) {
    return pdfValue / 72f * targetDpi;
}

Program.vb

Imports System.Drawing
Imports System.Collections.Generic
Imports DevExpress.Pdf

Private Const DrawingDpi As Single = 72F

Shared Sub Main(ByVal args() As String)
    Using processor As New PdfDocumentProcessor()
        processor.LoadDocument("..\..\RotatedDocument.pdf")
        Using textBrush As New SolidBrush(Color.FromArgb(100, Color.Blue))
            AddGraphics(processor, "text", textBrush)
        End Using
        processor.SaveDocument("..\..\RotatedDocumentWithGraphics.pdf")
    End Using
End Sub

Shared Sub AddGraphics(ByVal processor As PdfDocumentProcessor, ByVal text As String, ByVal textBrush As SolidBrush)
    Dim pages As IList(Of PdfPage) = processor.Document.Pages
    For i As Integer = 0 To pages.Count - 1
        Dim page As PdfPage = pages(i)
        Using graphics As PdfGraphics = processor.CreateGraphics()
            Dim actualPageSize As SizeF = PrepareGraphics(page, graphics, DrawingDpi, DrawingDpi)
            Using font As New Font("Segoe UI", 20, FontStyle.Regular)
                Dim textSize As SizeF = graphics.MeasureString(text, font, PdfStringFormat.GenericDefault)
                Dim topLeft As New PointF(0, 0)
                Dim bottomRight As New PointF(actualPageSize.Width - textSize.Width, actualPageSize.Height - textSize.Height)
                graphics.DrawString(text, font, textBrush, topLeft)
                graphics.DrawString(text, font, textBrush, bottomRight)
                graphics.AddToPageForeground(page, DrawingDpi, DrawingDpi)
            End Using
        End Using
    Next i
End Sub

Shared Function PrepareGraphics(ByVal page As PdfPage, ByVal graphics As PdfGraphics, ByVal dpiX As Single, ByVal dpiY As Single) As SizeF
    Dim cropBox As PdfRectangle = page.CropBox
    Dim cropBoxWidth As Single = ConvertFromPdfUnits(CSng(cropBox.Width), dpiX)
    Dim cropBoxHeight As Single = ConvertFromPdfUnits(CSng(cropBox.Height), dpiY)
    Select Case page.Rotate
        Case 90
            graphics.RotateTransform(-90)
            graphics.TranslateTransform(-cropBoxHeight, 0)
            Return New SizeF(cropBoxHeight, cropBoxWidth)
        Case 180
            graphics.RotateTransform(-180)
            graphics.TranslateTransform(-cropBoxWidth, -cropBoxHeight)
            Return New SizeF(cropBoxWidth, cropBoxHeight)
        Case 270
            graphics.RotateTransform(-270)
            graphics.TranslateTransform(0, -cropBoxWidth)
            Return New SizeF(cropBoxHeight, cropBoxWidth)
    End Select
    Return New SizeF(cropBoxWidth, cropBoxHeight)
End Function

Shared Function ConvertFromPdfUnits(ByVal pdfValue As Single, ByVal targetDpi As Single) As Single
    Return pdfValue / 72F * targetDpi
End Function