'''' This code is part of Document Solutions for PDF .NET demos.'' Copyright (c) MESCIUS inc. All rights reserved.''Imports SystemImports System.IOImports System.DrawingImports System.NumericsImports GrapeCity.Documents.PdfImports GCTEXT = GrapeCity.Documents.Text
'' This sample shows how to add a simple text watermark-Like overlay'' to all pages of an existing PDF.Public Class AddWatermark    Function CreatePDF(ByVal stream As Stream) As Integer        Dim doc = New GcPdfDocument()        Using fs = File.OpenRead(Path.Combine("Resources", "PDFs", "SlidePages.pdf"))            doc.Load(fs)            For Each page In doc.Pages                Dim g = page.Graphics
                '' Text layout used to draw the 'watermark':                Dim tl = g.CreateTextLayout()                tl.Append("DsPdf Demo")                tl.DefaultFormat.Font = GCTEXT.Font.FromFile(Path.Combine("Resources", "Fonts", "NotoSans-Bold.ttf"))                tl.DefaultFormat.FontSize = g.Resolution                '' Semi-transparent color:                tl.DefaultFormat.ForeColor = Color.FromArgb(128, Color.Yellow)                tl.DefaultFormat.GlyphAdvanceFactor = 1.5F                tl.PerformLayout()
                '' Rotation angle (radians) - from left/bottom to right/top corners of the page:                Dim angle = -Math.Asin(g.CanvasSize.Width / g.CanvasSize.Height)                '' Page center:                Dim center = New PointF(g.CanvasSize.Width / 2, g.CanvasSize.Height / 2)                '' Additional offset from text size:                Dim delta = New PointF(                    ((tl.ContentWidth * Math.Cos(angle) - tl.ContentHeight * Math.Sin(angle)) / 2),                    ((tl.ContentWidth * Math.Sin(angle) + tl.ContentHeight * Math.Cos(angle)) / 2))
                '' Draw watermark text diagonally in the center of the page                '' (matrix transforms are applied from last to first):                g.Transform =                    Matrix3x2.CreateRotation(angle) *                    Matrix3x2.CreateTranslation(center.X - delta.X, center.Y - delta.Y)                g.DrawTextLayout(tl, PointF.Empty)                g.Transform = Matrix3x2.Identity            Next            doc.Save(stream)        End Using        Return doc.Pages.Count    End FunctionEnd Class