'''' This code is part of Document Solutions for PDF .NET demos.'' Copyright (c) MESCIUS inc. All rights reserved.''Imports System.IOImports System.DrawingImports System.NumericsImports GrapeCity.Documents.PdfImports GCTEXT = GrapeCity.Documents.TextImports GCDRAW = GrapeCity.Documents.Drawing
Public Class TransparencyLayer    Public 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                tl.DefaultFormat.ForeColor = Color.Blue                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(                    CSng((tl.ContentWidth * Math.Cos(angle) - tl.ContentHeight * Math.Sin(angle)) / 2),                    CSng((tl.ContentWidth * Math.Sin(angle) + tl.ContentHeight * Math.Cos(angle)) / 2))
                ' Create semi-opaque transparency layer. All subsequent drawing operations                ' will be drawn using the specified opacity till the PopTransparencyLayer() call:                g.PushTransparencyLayer(Nothing, 0.5F)
                ' Draw watermark text diagonally in the center of the page                ' (matrix transforms are applied from last to first):                g.Transform =                    Matrix3x2.CreateRotation(CSng(angle)) *                    Matrix3x2.CreateTranslation(center.X - delta.X, center.Y - delta.Y)                g.DrawTextLayout(tl, PointF.Empty)                ' Add a border around the text, it will also be drawn semi-transparently:                Dim rc = New RectangleF(-30, -20, tl.ContentWidth + 60, tl.ContentHeight + 40)                g.DrawRoundRect(rc, 30, New GCDRAW.Pen(Color.DarkOrange, 8))                g.Transform = Matrix3x2.Identity
                ' Pop transparency layer:                g.PopTransparencyLayer()            Next            doc.Save(stream)            Return doc.Pages.Count        End Using    End FunctionEnd Class