public static void Encode(Image image, string filePath)
{
using (var fileStream = File.Open(filePath, FileMode.Create))
{
Encode(image, fileStream);
}
}
public static void Encode(Image image, Stream stream)
{
stream.WriteString(image.Header);
stream.WriteBytes(image.LogicalScreenDescriptor.ToBytes());
if (image.LogicalScreenDescriptor.GlobalColorTableFlag)
{
stream.WriteBytes(image.GlobalColorTable);
}
foreach (var applicationExtension in image.ApplictionExtensions)
{
stream.WriteBytes(applicationExtension.ToBytes());
}
foreach (var commentExtension in image.CommentExtensions)
{
stream.WriteBytes(commentExtension.ToBytes());
}
WriteFrames(image.Frames, stream);
}
public static Image Decode(Stream stream)
{
var result = new Image
{
Header = stream.ReadString(6),
LogicalScreenDescriptor = LogicalScreenDescriptor.Read(stream)
};
if (result.LogicalScreenDescriptor.GlobalColorTableFlag)
{
result.GlobalColorTable = stream.ReadBytes(result.LogicalScreenDescriptor.GlobalColorTableSize * 3);
}
GraphicControlExtension graphicControlExtension = null;
var componentType = stream.ReadByte();
while (componentType != 0)
{
if (componentType == ImageDescriptor.ImageSeparator)
{
var imageFrame = ReadImageFrame(stream, result.GlobalColorTable, graphicControlExtension);
result.Frames.Add(imageFrame);
}
else if (componentType == Const.ExtensionIntroducer)
{
var extensionType = stream.ReadByte();
switch (extensionType)
{
case GraphicControlExtension.GraphicControlLabel:
{
graphicControlExtension = GraphicControlExtension.Read(stream);
break;
}
case CommentExtension.CommentLabel:
{
var commentExtension = CommentExtension.Read(stream);
result.CommentExtensions.Add(commentExtension);
break;
}
case ApplicationExtension.ExtensionLabel:
{
var applicationExtension = ApplicationExtension.Read(stream);
result.ApplictionExtensions.Add(applicationExtension);
break;
}
case PlainTextExtension.PlainTextLabel:
{
var plainTextExtension = PlainTextExtension.Read(stream);
result.PlainTextEntensions.Add(plainTextExtension);
break;
}
}
}
else if (componentType == Const.EndIntroducer)
{
break;
}
componentType = stream.ReadByte();
}
return result;
}
private static void ProcessDisposalMethod(Image image)
{
Bitmap lastBitmap = null;
var lastDisposal = 0;
var index = 0;
foreach (var frame in image.Frames)
{
var offsetX = frame.ImageDescriptor.ImageLeftPosition;
var offsetY = frame.ImageDescriptor.ImageTopPosition;
var frameWidth = frame.ImageDescriptor.ImageWidth;
var frameHeight = frame.ImageDescriptor.ImageHeight;
if (frame.Bitmap.Width != image.Width || frame.Bitmap.Height != image.Height)
{
frame.ImageDescriptor.ImageLeftPosition = 0;
frame.ImageDescriptor.ImageTopPosition = 0;
frame.ImageDescriptor.ImageWidth = image.Width;
frame.ImageDescriptor.ImageHeight = image.Height;
}
var transparentColorIndex = -1;
if (frame.GraphicControlExtension != null && frame.GraphicControlExtension.TransparentColorFlag)
{
transparentColorIndex = frame.GraphicControlExtension.TransparentColorIndex;
}
if (frameWidth != image.Width || frameHeight != image.Height || index != 0)
{
var bgColor = Convert.ToInt32(image.GlobalColorIndexedTable[transparentColorIndex]);
var color = Color.FromArgb(bgColor);
var bitmap = new Bitmap(image.Width, image.Height);
using (var graphics = Graphics.FromImage(bitmap))
{
if (lastBitmap != null)
{
graphics.DrawImageUnscaled(lastBitmap, new Point(0, 0));
}
if (frame.GraphicControlExtension != null && frame.GraphicControlExtension.DisposalMethod == 1)
{
graphics.DrawRectangle(new Pen(new SolidBrush(color)), new Rectangle(offsetX, offsetY, frameWidth, frameHeight));
}
if (frame.GraphicControlExtension != null && frame.GraphicControlExtension.DisposalMethod == 2 && lastDisposal != 1)
{
graphics.Clear(color);
}
graphics.DrawImageUnscaled(frame.Bitmap, new Point(offsetX, offsetY));
}
frame.Bitmap.Dispose();
frame.Bitmap = bitmap;
}
lastBitmap = frame.Bitmap;
DefaultQuantizer.Quantize(frame.Bitmap, frame.GetPalette());
if (frame.GraphicControlExtension != null)
{
lastDisposal = frame.GraphicControlExtension.DisposalMethod;
}
index++;
}
}
