/// <summary>
/// Writes the image descriptor to the stream.
/// </summary>
/// <param name="image">The <see cref="QuantizedImage"/> containing indexed pixels.</param>
/// <param name="quality">The quality (number of colors) to encode the image to.</param>
/// <param name="stream">The stream to write to.</param>
private void WriteImageDescriptor(QuantizedImage image, int quality, Stream stream)
{
this.WriteByte(stream, GifConstants.ImageDescriptorLabel); // 2c
// TODO: Can we capture this?
this.WriteShort(stream, 0); // Left position
this.WriteShort(stream, 0); // Top position
this.WriteShort(stream, image.Width);
this.WriteShort(stream, image.Height);
// Calculate the quality.
int bitDepth = this.GetBitsNeededForColorDepth(quality);
// No LCT use GCT.
this.WriteByte(stream, 0);
// Write the image data.
this.WriteImageData(image, stream, bitDepth);
}
/// <summary>
/// Writes the image pixel data to the stream.
/// </summary>
/// <param name="image">The <see cref="QuantizedImage"/> containing indexed pixels.</param>
/// <param name="stream">The stream to write to.</param>
/// <param name="bitDepth">The bit depth of the image.</param>
private void WriteImageData(QuantizedImage image, Stream stream, int bitDepth)
{
byte[] indexedPixels = image.Pixels;
LzwEncoder encoder = new LzwEncoder(indexedPixels, (byte)bitDepth);
encoder.Encode(stream);
this.WriteByte(stream, GifConstants.Terminator);
}
