'''' This code is part of Document Solutions for Imaging demos.'' Copyright (c) MESCIUS inc. All rights reserved.''Imports System.IOImports System.DrawingImports System.Collections.GenericImports System.LinqImports System.NumericsImports GrapeCity.Documents.DrawingImports GrapeCity.Documents.TextImports GrapeCity.Documents.Imaging
'' This sample loads an existing GIF and modifies its frames.'' Specifically, it applies a color matrix to change the colors,'' and flips the images horizontally.'' The GIF loaded in this sample is the one produced by IndexedGif.Public Class UpdateGif    Function GenerateImageStream(                ByVal targetMime As String,                ByVal pixelSize As Size,                ByVal dpi As Single,                ByVal opaque As Boolean,                Optional sampleParams As String() = Nothing) As Stream
        If Not targetMime = MimeTypes.GIF Then            Throw New Exception("This sample only supports GIF output format.")        End If
        '' Matrix to change colors to greenish blues:        Dim colorMatrix = New ColorMatrix5x4() With            {                .M11 = 0.2F,                .M12 = 0.3F,                .M22 = 0.5F            }
        Dim ms = New MemoryStream()        '' Read source GIF, write modified one (change palette And flip And rotate frames)        Using gr = New GcGifReader(Path.Combine("Resources", "Gifs", "goldfish-indexed.gif")), gw = New GcGifWriter(ms)
            Dim pal = gr.GetGlobalPalette()            '' This sample will only work with GIFs that have a global palette            If pal Is Nothing Then                Throw New Exception("Source GIF does not have a global palette.")            End If            '' Use color matrix to update the palette            Using palBmp = New GcBitmap(pal, pal.Length, 1, True)                palBmp.ApplyColorMatrix(colorMatrix)            End Using
            '' Set target paletter And other properties            gw.GlobalPalette = pal            gw.LogicalScreenWidth = gr.LogicalScreenWidth            gw.LogicalScreenHeight = gr.LogicalScreenHeight            gw.PixelAspectRatio = gr.PixelAspectRatio            gw.AllowAddingTransparentColor = False            Using tbmp = New GcBitmap()                For i = 0 To gr.Frames.Count - 1                    Dim frame = gr.Frames(i)                    frame.ToGcBitmap(tbmp, i - 1)
                    '' Flip the image horizontally (this will reverse the 'rotation' of the fish):                    Using bmp = tbmp.FlipRotate(FlipRotateAction.FlipHorizontal)                        '' Apply the color matrix And append the frame to the target GIF:                        bmp.ApplyColorMatrix(colorMatrix)                        gw.AppendFrame(bmp, pal, DitheringMethod.NoDithering, 0, 0, GifDisposalMethod.DoNotDispose, frame.DelayTime, False)                    End Using                Next            End Using        End Using        ms.Seek(0, SeekOrigin.Begin)        Return ms    End Function
    Public ReadOnly Property DefaultMime() As String        Get            Return MimeTypes.GIF        End Get    End PropertyEnd Class