'''' 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.ImagingImports GCTEXT = GrapeCity.Documents.TextImports GCDRAW = GrapeCity.Documents.Drawing
'' This sample demonstrates how quantization and dithering'' algorithms can be used to convert a 24 bits per pixel image'' to a reasonably looking image with a limited palette'' (16 colors, 4 bits per pixel).Public Class LimitedPalette    Function GenerateImage(        ByVal pixelSize As Size,        ByVal dpi As Single,        ByVal opaque As Boolean,        Optional ByVal sampleParams As String() = Nothing) As GcBitmap
        opaque = True
        Dim bmp = New GcBitmap(pixelSize.Width, pixelSize.Height, opaque, dpi, dpi)        Using origBmp = New GcBitmap()            '' Load a sample photo:            Dim imagePath = Path.Combine("Resources", "ImagesBis", "clivia.jpg")            Using stm = New FileStream(imagePath, FileMode.Open, FileAccess.Read, FileShare.Read, 4096, FileOptions.RandomAccess)                origBmp.Load(stm)            End Using
            '' Resize the original photo so we can place 4 samples of it            '' on the resulting bitmap:            Dim w = pixelSize.Width / 2            Dim h = pixelSize.Height / 2            Using sizedBmp = origBmp.Resize(w, h, InterpolationMode.Cubic)                '' Resized original image:                bmp.BitBlt(sizedBmp, 0, 0)
                '' Simple dithering                Using ind = sizedBmp.ToIndexed4bppBitmap(DitheringMethod.Stucki), bm = ind.ToGcBitmap()                    bmp.BitBlt(bm, w, 0)                End Using
                '' Octree quantizer algorithm without dithering                Using ind = sizedBmp.ToIndexed4bppBitmap(16), bm = ind.ToGcBitmap()                    bmp.BitBlt(bm, 0, h)                End Using
                '' Octree quantizer + dithering:                Dim pal = sizedBmp.GenerateOctreePalette(16)                Using ind = sizedBmp.ToIndexed4bppBitmap(pal, DitheringMethod.Stucki), bm = ind.ToGcBitmap()                    bmp.BitBlt(bm, w, h)                End Using            End Using
            '' Add borders between the quadrants, And captions for each:            Dim lineh = 2            Using g = bmp.CreateGraphics(Nothing)                Dim foreColor = Color.Yellow                Dim backColor = Color.Blue                Dim fnt = GCTEXT.Font.FromFile(Path.Combine("Resources", "Fonts", "FreeMono.ttf"))                g.DrawLine(w, 0, w, h * 2, New GCDRAW.Pen(Color.Gray, lineh * 2))                g.DrawLine(0, h, w * 2, h, New GCDRAW.Pen(Color.Gray, lineh * 2))                Dim tf = New TextFormat() With {.Font = fnt, .FontSize = 18, .ForeColor = foreColor, .BackColor = backColor, .FontBold = True}                Dim th = g.MeasureString("QWERTY", tf).Height                g.DrawString(" Original image (24bpp) ", tf, New PointF(0, h - th + lineh))                g.DrawString(" Simple dithering (4bpp) ", tf, New PointF(w + lineh, h - th + lineh))                g.DrawString(" Octree quantizer (4bpp) ", tf, New PointF(0, h * 2 + lineh - th + lineh))                g.DrawString(" Octree + dithering (4bpp) ", tf, New PointF(w + lineh, h * 2 + lineh - th + lineh))            End Using        End Using        Return bmp    End FunctionEnd Class