'''' This code is part of Document Solutions for Imaging demos.'' Copyright (c) MESCIUS inc. All rights reserved.''Imports System.IOImports System.DrawingImports GrapeCity.Documents.DrawingImports GrapeCity.Documents.TextImports GrapeCity.Documents.ImagingImports GCTEXT = GrapeCity.Documents.Text
'' This sample demonstrates the use of TransparencyMaskBitmap'' when drawing on a bitmap. The transparency mask used is'' created on the fly by filling an intermediary bitmap'' with a linear gradient brush from 0 (black, transparent)'' to 255 (white, opaque).Public Class TransparencyMask    Public Function GenerateImage(        ByVal pixelSize As Size,        ByVal dpi As Single,        ByVal opaque As Boolean,        Optional ByVal sampleParams As String() = Nothing) As GcBitmap
        Dim h2 As Integer = pixelSize.Width \ 2
        '' Prepare a linear gradient transparency mask,        '' from 0 (transparent) to 255 (opaque):        Using mask As New GcBitmap(h2, h2, True)            Using gmask = mask.CreateGraphics()                Dim grad = New LinearGradientBrush(Color.Black, Color.White)                gmask.FillRectangle(New RectangleF(0, 0, mask.Width, mask.Height), grad)            End Using            '' Convert to GrayscaleBitmap to be used as Renderer.TransparencyMaskBitmap:            Using gsb = mask.ToGrayscaleBitmap()
                '' Create a bitmap to draw on, fill it with yellow background:                Using bmp1 As New GcBitmap(h2, h2, True)                    Using g = bmp1.CreateGraphics(Color.Yellow)
                        '' Apply the transparency mask:                        g.Renderer.TransparencyMaskBitmap = gsb
                        '' Fill 3 circles, note how the fill gradually changes                        '' from transparent to opaque (left to right) along with the gradient:                        Dim d As Single = CSng(h2) / 25.0!                        Dim rc As New RectangleF(0, 0, h2 * 0.7F, h2 * 0.7F)
                        Dim bmp = New GcBitmap(pixelSize.Width, pixelSize.Height, True, dpi, dpi)                        bmp.Clear(Color.White)                        FillCircles(g, rc, h2, d)                        bmp.BitBlt(bmp1, 0, 0)
                        g.Renderer.TransparencyMaskBitmap = Nothing                        FillCircles(g, rc, h2, d)                        bmp.BitBlt(bmp1, h2, 0)
                        '' Add some explanatory texts below the images:                        Dim gg = bmp.CreateGraphics()                        rc = New RectangleF(0, h2 + d, h2 - d * 2, h2 - d * 2)                        Dim tf = New TextFormat() With {                            .Font = GCTEXT.Font.FromFile(Path.Combine("Resources", "Fonts", "FreeMono.ttf")),                            .FontSize = 16                        }                        gg.DrawString(                            "The circles in the image above were rendered with TransparencyMaskBitmap " &                            "on the target graphics set to a linear gradient from transparent to opaque.",                            tf, rc, TextAlignment.Center, ParagraphAlignment.Near)
                        rc.Offset(h2, 0)                        gg.DrawString(                            "The circles in the image above were rendered with no TransparencyMaskBitmap " &                            "on the target graphics.",                            tf, rc, TextAlignment.Center, ParagraphAlignment.Near)
                        Return bmp                    End Using                End Using            End Using        End Using    End Function
    Private Sub FillCircles(ByVal g As GcBitmapGraphics, ByVal rc As RectangleF, ByVal h2 As Single, ByVal d As Single)        Dim r = rc        r.Offset((h2 - rc.Width) / 2, 0)        r.Inflate(-d, -d)        g.FillEllipse(r, Color.Red)
        r = rc        r.Offset(h2 - rc.Width, h2 - rc.Height)        r.Inflate(-d, -d)        g.FillEllipse(r, Color.Green)
        r = rc        r.Offset(0, h2 - rc.Height)        r.Inflate(-d, -d)        g.FillEllipse(r, Color.Blue)    End SubEnd Class