//
// This code is part of GrapeCity Documents for Imaging samples.
// Copyright (c) GrapeCity, Inc. All rights reserved.
//
using System;
using System.IO;
using System.Drawing;
using GrapeCity.Documents.Imaging;
using GrapeCity.Documents.Drawing;
namespace GcImagingWeb.Samples
{
// This sample loads an existing GIF with true color frames
// (produced by the MakeGif sample) and converts its frames
// to indexed 8bpp images. It also adds a global palette to the
// resulting GIF (the palette is taken from the first frame).
public class IndexedGif
{
public Stream GenerateImageStream(ImageEncoding targetEncoding, Size pixelSize, float dpi, bool opaque, string[] sampleParams = null)
{
if (targetEncoding != ImageEncoding.Gif)
throw new Exception("This sample only supports GIF output format.");
var ms = new MemoryStream();
// Read frames from the source GIF, convert them to 8bpp and save in the target GIF:
using (var gr = new GcGifReader(Path.Combine("Resources", "Gifs", "goldfish.gif")))
using (var gw = new GcGifWriter(ms))
{
for (int i = 0; i < gr.Frames.Count; ++i)
{
// Add a global palette to the target GIF based on the first frame:
if (i == 0)
using (var tbmp = gr.Frames[i].ToGcBitmap())
gw.GlobalPalette = tbmp.GenerateOctreePalette(256);
var indexedBmp = gr.Frames[i].ReadAsIndexed8bppBitmap();
gw.AppendFrame(indexedBmp, 0, 0, GifDisposalMethod.DoNotDispose, 16);
}
}
ms.Seek(0, SeekOrigin.Begin);
return ms;
}
public ImageEncoding DefaultEncoding { get => ImageEncoding.Gif; }
}
}