/// <summary>
/// Writes the graphics control extension to the stream.
/// </summary>
/// <typeparam name="TPixel">The pixel format.</typeparam>
/// <param name="image">The <see cref="ImageBase{TPixel}"/> to encode.</param>
/// <param name="metaData">The metadata of the image or frame.</param>
/// <param name="writer">The stream to write to.</param>
/// <param name="transparencyIndex">The index of the color in the color palette to make transparent.</param>
private void WriteGraphicalControlExtension <TPixel>(ImageBase <TPixel> image, IMetaData metaData, EndianBinaryWriter writer, int transparencyIndex)
where TPixel : struct, IPixel <TPixel>
{
GifGraphicsControlExtension extension = new GifGraphicsControlExtension()
{
DisposalMethod = metaData.DisposalMethod,
TransparencyFlag = transparencyIndex < 255,
TransparencyIndex = transparencyIndex,
DelayTime = metaData.FrameDelay
};
// Write the intro.
this.buffer[0] = GifConstants.ExtensionIntroducer;
this.buffer[1] = GifConstants.GraphicControlLabel;
this.buffer[2] = 4;
writer.Write(this.buffer, 0, 3);
PackedField field = default(PackedField);
field.SetBits(3, 3, (int)extension.DisposalMethod); // 1-3 : Reserved, 4-6 : Disposal
// TODO: Allow this as an option.
field.SetBit(6, false); // 7 : User input - 0 = none
field.SetBit(7, extension.TransparencyFlag); // 8: Has transparent.
writer.Write(field.Byte);
writer.Write((ushort)extension.DelayTime);
writer.Write((byte)extension.TransparencyIndex);
writer.Write(GifConstants.Terminator);
}
/// <summary>
/// Reads the graphic control extension.
/// </summary>
private void ReadGraphicalControlExtension()
{
this.currentStream.Read(this.buffer, 0, 6);
byte packed = this.buffer[1];
this.graphicsControlExtension = new GifGraphicsControlExtension
{
DelayTime = BitConverter.ToInt16(this.buffer, 2),
TransparencyIndex = this.buffer[4],
TransparencyFlag = (packed & 0x01) == 1,
DisposalMethod = (DisposalMethod)((packed & 0x1C) >> 2)
};
}
/// <summary>
/// Writes the graphics control extension to the stream.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <typeparam name="TPacked">The packed format. <example>uint, long, float.</example></typeparam>
/// <param name="image">The <see cref="ImageBase{TColor, TPacked}"/> to encode.</param>
/// <param name="writer">The stream to write to.</param>
/// <param name="transparencyIndex">The index of the color in the color palette to make transparent.</param>
private void WriteGraphicalControlExtension <TColor, TPacked>(ImageBase <TColor, TPacked> image, EndianBinaryWriter writer, int transparencyIndex)
where TColor : struct, IPackedPixel <TPacked>
where TPacked : struct
{
// TODO: Check transparency logic.
bool hasTransparent = transparencyIndex > -1;
DisposalMethod disposalMethod = hasTransparent
? DisposalMethod.RestoreToBackground
: DisposalMethod.Unspecified;
GifGraphicsControlExtension extension = new GifGraphicsControlExtension()
{
DisposalMethod = disposalMethod,
TransparencyFlag = hasTransparent,
TransparencyIndex = transparencyIndex,
DelayTime = image.FrameDelay
};
// Reduce the number of writes.
byte[] intro =
{
GifConstants.ExtensionIntroducer,
GifConstants.GraphicControlLabel,
4 // Size
};
writer.Write(intro);
PackedField field = default(PackedField);
field.SetBits(3, 3, (int)extension.DisposalMethod); // 1-3 : Reserved, 4-6 : Disposal
// TODO: Allow this as an option.
field.SetBit(6, false); // 7 : User input - 0 = none
field.SetBit(7, extension.TransparencyFlag); // 8: Has transparent.
writer.Write(field.Byte);
writer.Write((ushort)extension.DelayTime);
writer.Write((byte)(extension.TransparencyIndex == -1 ? 255 : extension.TransparencyIndex));
writer.Write(GifConstants.Terminator);
}
/// <summary>
/// Writes the graphics control extension to the stream.
/// </summary>
/// <typeparam name="TColor">The pixel format.</typeparam>
/// <param name="image">The <see cref="ImageBase{TColor}"/> to encode.</param>
/// <param name="metaData">The metadata of the image or frame.</param>
/// <param name="writer">The stream to write to.</param>
/// <param name="transparencyIndex">The index of the color in the color palette to make transparent.</param>
private void WriteGraphicalControlExtension <TColor>(ImageBase <TColor> image, IMetaData metaData, EndianBinaryWriter writer, int transparencyIndex)
where TColor : struct, IPackedPixel, IEquatable <TColor>
{
// TODO: Check transparency logic.
bool hasTransparent = transparencyIndex < 255;
DisposalMethod disposalMethod = hasTransparent
? DisposalMethod.RestoreToBackground
: DisposalMethod.Unspecified;
GifGraphicsControlExtension extension = new GifGraphicsControlExtension()
{
DisposalMethod = disposalMethod,
TransparencyFlag = hasTransparent,
TransparencyIndex = transparencyIndex,
DelayTime = metaData.FrameDelay
};
// Write the intro.
this.buffer[0] = GifConstants.ExtensionIntroducer;
this.buffer[1] = GifConstants.GraphicControlLabel;
this.buffer[2] = 4;
writer.Write(this.buffer, 0, 3);
PackedField field = default(PackedField);
field.SetBits(3, 3, (int)extension.DisposalMethod); // 1-3 : Reserved, 4-6 : Disposal
// TODO: Allow this as an option.
field.SetBit(6, false); // 7 : User input - 0 = none
field.SetBit(7, extension.TransparencyFlag); // 8: Has transparent.
writer.Write(field.Byte);
writer.Write((ushort)extension.DelayTime);
writer.Write((byte)extension.TransparencyIndex);
writer.Write(GifConstants.Terminator);
}
